Comments on Draft Transmission Plan

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

ACP-California greatly appreciates CAISO’s efforts to conduct studies and propose transmission solutions in the 2025-26 Draft Transmission Plan. CAISO has undertaken significant work and is proposing a notable set of projects to advance reliability across the system. ACP-California supports the reliability-driven project set recommended for approval in the Draft 2025-26 Transmission Plan. The 33 projects reflect a reasonable response to the load growth and system conditions documented in the plan. ACP-California also notes that three reliability projects in this cycle are categorized as utilizing advanced conductors or other grid-enhancing technologies (GETs) and supports the deployment of GETs where technically and economically appropriate.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

ACP-California greatly appreciates the work of the CAISO team (as well as the work of the CPUC IRP team) to evaluate policy-driven transmission projects to support access to a broad set of generation and storage resources. ACP-California supports moving forward with approval of the policy-driven projects proposed in the 2025-26 Draft Transmission Plan.

ACP-California strongly supports approval of the Trout Canyon–Lugo 500 kV line which may be the most important project in the 2025-26 Draft Transmission Plan for promoting clean energy development to meet California's needs. CAISO has indicated this project unlocks roughly 7 GW of resource deliverability in the Lugo-Victorville area and helps to address East of Pisgah constraints which have caused the 2025 TPD allocation cycle to be severely constrained for TPD allocations in this area. Trout Canyon–Lugo was previously proposed in the 2022-23 Draft Transmission Plan. However, the project did not proceed to approval at that time as CAISO needed to further investigate alternative project proposals. Since then, the severity of the constraints in the area have grown and the quantity of diverse, clean resources has grown as part of the CPUC’s TPP portfolios, now encompassing roughly 500 MW of geothermal, 4 GW of out-of-state wind, 1.6 GW or solar, 1.2 GW of in-state wind and 320 MW of batteries. Thus, this project is essential to achieving the diverse, reliable portfolio of clean energy resources California needs online in the next 10-15 years. We appreciate that the ISO has brought the Trout Canyon – Lugo project back in this plan and urge the ISO to expeditiously approve the project and move it through the competitive solicitation process.

ACP-California also appreciates CAISO’s efforts to continually evaluate previously approved projects to ensure that they continue to meet the needs of the state for reliability, affordability, and achieving policy objectives. ACP-California understands the CAISO’s reasoning for cancelling the Del Amo–Mesa–Serrano 500 kV project and proposing more cost-effective alternatives after the estimate grew from $1.125 billion at approval to $5.0 billion at the detailed engineering stage. The Del Amo–Mesa–Serrano project clearly warranted reevaluation, and the ISO's willingness to reconsider and propose alternative solutions based on updated portfolios is an appropriate outcome.

However, it is critical for CAISO and other stakeholders to understand that there are significant impacts associated with the cancellation of transmission projects such as this one, particularly given how CAISO has so strictly aligned the interconnection queue process with the availability of Transmission Plan Deliverability (TPD) at particular points of interconnection (POIs). The cancellation of this project will result in a loss of TPD at project interconnection locations (most notably Lugo) where there was previously TPD available. The ISO’s latest assessments indicate that the removal of the Serrano project from planning models resulted in the identification of a new Mira Loma–Mesa area constraint. This downstream constraint currently traps the deliverability of generators in the East of Pisgah (EOP) and North of Lugo areas; notably, the 2025 Transmission Plan Deliverability (TPD) study found that no deliverability could be allocated to seeking generators in these regions specifically because of this new Mira Loma–Mesa limitation.

This will likely make a significant number of projects in the queue in the East of Pisgah area no longer viable for continued development given the loss of TPD at their POIs. Many of these projects – absent the cancellation of this transmission upgrade – were likely viable for development and commercialization, having entered the queue in C14 or C15.In fact, it is likely that developers requested project interconnection locations in large part due to the anticipated availability of TPD for Cluster 15 interconnection requests. We understand that TPD – at specific POIs – will be lost with the cancellation of Del Amo–Mesa–Serano line and will not be fully mitigated by approval of other projects in the area (e.g., the Mesa - Laguna Bell 230 kV #2 Upgrade). In addition, ACP-California understands that part of the alternative solution includes additional battery storage that has been mapped to locations downstream of the constraint in the LA basin. However, development of a large amount of battery storage in this region may be highly challenging, especially given the increase in local opposition to battery projects in recent months.[1]

As a result, we recommend the CAISO evaluate and consider proposing additional solutions to provide deliverability for EOP resources into the LA Basin as part of the final 2025-2026 TPP. This need is urgent given the quantity or new resources forecast as necessary in the TPP portfolios, including the over 7 GW of resources expected from the EOP region by 2035. If CAISO waits until the next cycle to approve additional deliverability solutions, many of these resources may need to defer to C17 to proceed with development. For C14 projects, that would represent a delay of 7 years, potentially hindering commercial viability.

ACP-California strongly supports CAISO’s reevaluation of projects to propose more cost-effective alternatives, as such an approach is essential to supporting affordability and promoting efficient grid expansion.  However, going forward, we ask that CAISO also consider the downstream impacts of project cancellation, given the recent interconnection process changes restrict project interconnection locations to specific POIs based on the then current availability of TPD at that location. While the Trout Canyon–Lugo project successfully resolves local interconnection issues, a comprehensive long-term solution must also address this downstream constraint to ensure that carbon-free generators are not ultimately blocked from delivering their power to California load centers.

While we’re seeking a solution to the remaining Trout Canyon-Lugo constraint this cycle, ACP-California also sees opportunities for improvement going forward. As CAISO moves to a two-year TPP cycle, it should incorporate an evaluation of the impact of TPP projects it is considering cancelling on generation/storage projects in the interconnection queue. As part of a two-year planning cycle, CAISO should consider additional upgrades that would mitigate the negative impacts on projects proceeding through the interconnection queue.

[1] See: https://www.latimes.com/environment/story/2026-04-23/california-is-ground-zero-for-growing-battery-opposition

3. Please provide your organization’s comments on the Economic Assessment.

ACP-California appreciates CAISO’s economic assessment and recognition of the growing need to address congestion on Path 15 in the 2025-26 Draft Transmission Plan. ACP-California has previously commented that it may be appropriate to conduct an evaluation of the Transmission Economic Assessment Methodology (TEAM), given that it appears to under-report benefits of projects that can address significant congestion on the CAISO system. ACP-California was concerned TEAM might be so conservative that CAISO would not come forward recommending projects to address the significant congestion the system is expected to experience. But we are encouraged to see CAISO has determined mitigation is economic – when using the more appropriate congestion revenue treatment[1] – and that CAISO is looking at a phased approval process to address congestion on Path 15. We observe the CAISO’s examination of 19 preliminary alternatives for resolving the Path 15 corridor as indication that it is serious in its intent to bring forward a solution next cycle. We also commend the CAISO for considering the Path 15 corridor more broadly as extending North to Tesla and South to Whirlwind. Altogether, we support the CAISO’s proposed phased approval for the Path 15 corridor as it will provide time for analysis of the complex system dynamics associated with a more complete solution.

Specific to the 2025-26 Draft Transmission Plan, ACP-California supports approval of the Gates–Los Banos #3 500 kV Line Series Compensation as a reasonable near-term solution which does not foreclose more significant future upgrades to address Path 15 congestion, as the CAISO intends to put forward in the 2026-27 TPP. Specifically, CAISO believes Alternative 6 (the new Windhub–Tesla 500 kV line with Midway and Gates ties) is likely to be recommended for approval in the next planning cycle, pending additional assessments of its impacts on the system, especially given the complex interactions between Path 15 and Path 26. ACP-California supports expeditiously conducting the necessary analyses so that a larger solution for congestion on Path 15 – whether that is Alternative 6 or another alternative the ISO identifies as preferable – is ready for approval in the 2026-27 TPP. Path 15 congestion costs have grown sharply in recent cycles, and the economic case for a larger fix is no longer marginal. We greatly appreciate the CAISO’s efforts to evaluate and consider alternatives to help mitigate these costs and improve resource access and enhance economic system flows.

Although the Path 15 corridor was identified as a potential economic-driven upgrade, we also emphasize the importance of such and upgrade for increasing capacity and deliverability for several clean energy resource zones in-state, including Fresno solar and storage, Kern county solar and storage, and central coast offshore wind. We encourage the CPUC to work with the CAISO to integrate these resources into its TPP planning in such a manner that maximizes the economic and policy benefits of a Path 15 corridor project.

[1] ACP-California also supports CAISO plans to update the congestion revenue allocation within TEAM in 2026 and looks forward to additional stakeholder discussions on the planned updates and other TEAM-updates that may be appropriate.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

While ACP-California appreciates CAISO’s development of the MIC Expansion Request process, we note it remains insufficient to provide the commercial certainty that LSEs and generators require and to address the scale of out-of-state resource development now embedded in CPUC portfolios. ACP-California, along with other parties, have encouraged CAISO to take up a MIC Enhancements initiative in 2026/27 and we continue to encourage CAISO to do so, given that the MIC Expansion Request process has not been sufficient to address ongoing needs to reform MIC.

5. Please provide your organization’s comments on Frequency Response.

ACP-California appreciates the ISO's continued attention to frequency response as inverter-based resources (IBR) displace conventional synchronous generation on the CAISO system. The study finds that enabling frequency response on IBRs (particularly battery storage) materially improves system recovery from frequency events. As the share of IBRs on the system continues to grow, ACP-California encourages the ISO to examine whether existing market products adequately compensate battery storage resources for providing the headroom-based frequency response the study demonstrates is valuable. To take advantage of these BESS capabilities where installed, there must be operational incentives to support them.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

No additional comments at this time.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

3. Please provide your organization’s comments on the Economic Assessment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

Balanced Rock Power supports GridLiance West's initiative to construct the Trout Canyon - Lugo 500 kV project and supports the project advancing into the final 2025-2026 TPP. 

The proposed solution is a robust reliability solution which addresses some of the most binding and persistent constraints on the system such as the Lugo-Victorville constraint (which resulted in East of Pisgah being a merchant zone in C15). This upgrade could help enable deliverability for large volumes of generation from the East of Pisgah study area which are needed to meet California's energy targets. It is also a more durable solution versus relying on incremental fixes or RAS schemes in the coming years.

The Trout Canyon-Lugo 500 kV project is a long awaited upgrade intended to remove the bottleneck for moving power from the East of Pisgah region to the LA Basin. While some additional downstream upgrades will be needed, this upgrade provides a path for all generation types to reach urban load pockets. 

3. Please provide your organization’s comments on the Economic Assessment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

The Bay Area Municipal Transmission group (BAMx)^[1] appreciates the opportunity to comment on the CAISO’s 2025-2026 Draft Transmission Plan (“Draft Plan”) posted on April 7, 2026, and the material presented at the CAISO Stakeholder meeting on April 15, 2026. BAMx recognizes the tremendous amount of work the CAISO staff has completed in this planning cycle. However, as noted below, several material inconsistencies exist in the reporting of the assumptions and results in the Draft Plan and its appendices, which need to be corrected in the Revised Final Plan. BAMx supports transparent, internally consistent, and reproducible transmission planning analyses. Addressing the internal inconsistencies between the Draft Plan and Appendix B, and reconciling the Appendix C reliability results with the posted final power-flow cases, would significantly improve the clarity and credibility of the Draft Plan and facilitate more effective stakeholder review. BAMx also believes the CAISO staff must allow a corresponding amount of time to engage the stakeholders to explain the staff’s work.

1. Inconsistencies Between the Draft Plan and Appendix B Regarding the South Bay Reinforcement Project
   
   BAMx has identified material internal inconsistencies between the description of the Project in the Draft Plan and the presentation of the project scope in Appendix B. Specifically, the project scope described in the body of the Draft Plan appears to align with the scope approved in the 2024–2025 Transmission Plan, when the South Bay Reinforcement Project was originally approved. In contrast, Appendix B presents an “Original Scope” for the same project that differs materially from the scope described in the Draft Plan, including differences in how individual upgrade elements are defined and ordered.

At the same time, BAMx observes that the “Revised Scope” elements described in Appendix B appear internally consistent with the ordering and configuration presented in that appendix, rather than with the “Original Scope” as labeled in Appendix B. As a result, it is unclear how the revisions described in Appendix B map to the originally approved configuration reflected in the Draft Plan text.

This misalignment between:

• the Draft Plan narrative[2],
• the “Original Scope” description in Appendix B[3], and
• the “Revised Scope” elements presented in Appendix B[4]

creates substantial ambiguity as to what configuration was originally approved versus what configuration is now proposed for modification.

BAMx therefore requests that the CAISO revise Appendix B to ensure that the ordering, labeling, and description of original scope elements are fully aligned with the configuration previously approved and reflected in the Draft Plan, such that any proposed revised scope elements clearly and transparently correspond to the appropriate original project components. This clarification is necessary for stakeholders to meaningfully assess the nature and justification of the proposed scope changes.

2. Lack of Reproducibility Between Appendix C Reliability Results and Posted Final Power-Flow Cases

BAMx is also concerned that the reliability power-flow results presented in Appendix C do not appear to be reproducible using the final reliability power-flow cases posted to the CAISO Market Participant Portal (“MPP”).

In reviewing the South Bay area reliability results, BAMx notes that several overloads identified in Appendix C are not observed when the same contingencies are simulated using the final reliability cases currently posted to the MPP. This discrepancy raises questions regarding:

• whether Appendix C results were produced using updated or unpublished modeling assumptions,
• whether differences exist between the cases used for Appendix C and those posted for stakeholder review, or
• whether certain contingency definitions or system configurations differ between the two datasets.

This lack of reconciliation is particularly material where Appendix C results appear to inform revised project scopes or recommendations for approval. Absent a clear reconciliation, stakeholders are unable to independently validate or replicate the reliability findings presented in Appendix C, particularly with respect to the South Bay area.

BAMx respectfully requests that the CAISO clarify the relationship between the Appendix C results and the final reliability power-flow cases posted to the MPP, including whether:

• additional case modifications were applied for Appendix C analyses,
• different contingency definitions were used, or
• updated assumptions were incorporated that are not reflected in the posted cases.

Providing this clarification—and, if necessary, updated or annotated power-flow cases—would materially improve transparency and allow stakeholders to meaningfully assess the reliability basis for the proposed projects.

3. Need Additional Clarifications/Justifications for Selected Projects Recommended for Approval

1. Mariposa 70 kV Reactive Support

The Draft Plan recommends adding voltage support at Mariposa Substation, as this project would mitigate the low-voltage issue mentioned above and protect against the NERC TPL-001-5 Category P1 violation.[5] Did CAISO consider closing the normally open breaker on the Mariposa-Exchequer-Yosemite 70 kV line and raising the scheduled voltage at Exchequer as a potential mitigation? Also, the Draft Plan recommends installing a 20 MVAr voltage support device at Mariposa Substation. In particular, installing a 20 MVAr STATCOM at Mariposa Substation.[6] Did CAISO consider a shunt capacitor instead of a STATCOM device for this mitigation? Shunt capacitors at this size are a lower cost solution and may be flexible enough to fix these voltage issues at 70 kV.

2. Monta Vista – Loyola – Los Altos 60 kV Line Reconductoring

Did CAISO consider closing the Normally Open breaker on the Loyola to Los Altos-Cooley Landing 60 kV line as a potential mitigation to address the 3% overload on the Loyola – Los Altos section of the 60 kV line? BAMx seeks clarification as to whether this alternative configuration was evaluated as a potential screening-level mitigation. Furthermore, if the overload persists in 2040, then reconductoring only the 3.2-mile section of the Loyola – Los Altos section of the Monta Vista – Loyola – Los Altos 60 kV line might be adequate.[7] BAMx urges further review of this project recommended for approval.

3. Monta Vista 230/115 kV Transformer Bank Addition

The cost estimate of $104 million for the Monta Vista 230/115 kV Transformer Bank Addition is considerably higher than other similar scoped projects with the same Transformer Bank ratings like Newark ($63 million) and San Jose B ($69 million) 230/115 kV Bank Addition.[8]Please explain why the cost of this Bank Addition has a higher cost.

[1] BAMx consists of City of Palo Alto Utilities and City of Santa Clara, Silicon Valley Power.

[2] Draft Plan, pp.85-86.

[3] Appendix B, pp. B-110 – B-111.

[4] Appendix B, p. B-111

[5] Draft Plan, pp. 49-50.

[6] CAISO’s April 15^th Presentation, p. 27.

[7] CAISO’s April 15^th Presentation, p. 38.

[8] Draft Plan, p.8.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

1. Justification for East Shore 230 kV Area Reinforcement Project Needs Further Review

Appendix F cites thermal overloading of the Pittsburg-San Mateo 230 kV Line under NERC category P1 contingency as the justification for the East Shore 230 kV Area Reinforcement Project.[1] However, the contingency that entails the loss of Newark-Ravenswood 230 kV and Tesla-Ravenswood 230 kV lines, which BAMx understands to constitute a NERC TPL-001-5 Category P7 (common-mode) contingency, requires clarification as to how this contingency was treated in the Appendix F assessment.[2] Furthermore, BAMx seeks clarification on whether the CAISO has evaluated any of the reliability projects recommended by the CAISO in this Draft Plan, such as Tesla – Trimble – Metcalf 230 kV Corridor Expansion, to help alleviate this P7 overload on the Pittsburg-San Mateo 230 kV Line that is driving the need for the East Shore 230 kV Area Reinforcement. In other words, if the CAISO finds that some reliability projects help address the deliverability constraint, the CAISO should hold off approving the East Shore 230 kV Area Reinforcement Project in the current planning cycle. BAMx urges further review of this project recommended for approval.

2. Trout Canyon-Lugo 500 kV Line Approval Needs to be Followed by a Competitive Solicitation Process with Robust Cost Containment Measures

The East of Pisgah area policy-driven assessment identified severe portfolio resource deliverability limitations due to the GLW-VEA area constraint, Lugo – Victorville 500 kV constraint, Eldorado – McCullough 500 kV constraint, Victorville – McCullough 500 kV constraint and Sloan Canyon – Eldorado 500 kV constraint associated with the 2035 baseline and sensitivity portfolios and 2040 baseline portfolio under peak and off-peak scenarios.[3]

In the current transmission planning cycle, CAISO has now affirmatively recommended the Trout Canyon – Lugo 500 kV project for approval and have proposed to open it for competitive solicitation. In doing so, CAISO appears to have reaffirmed several core conclusions from the earlier cycle:

1. The Lugo – Victorville / East of Pisgah area requires a structural, transmission-based solution;
2. Reliance on incremental RAS expansion is not a durable or scalable long-term strategy; and
3. A new 500 kV facility provides system-level benefits that extend beyond mitigation of a single modeled constraint, including increased robustness, optionality, and policy-driven access to remote clean resources.

BAMx believes that the CAISO makes a good case for the justification for the Trout Canyon - Lugo 500 kV Line to address these deliverability constraints, but notes that this assessment is driven by portfolio resources behind the constraint, which are subject to high levels of uncertainty. Those include 3,000 MW of Wyoming wind connected to Eldorado and 1,100 MW of Idaho wind connected to Harry Allen, and a considerable amount of 4-hour and 8-hour battery storage. BAMx is concerned that if some of these resources do not materialize, it will drive down the need to build a project like the Trout Canyon - Lugo 500 kV line costing as high as $1.685 billion.[4]

Given that uncertainty, CAISO must remain nimble as the project advances. Competitive solicitation should be accompanied by strong cost-containment and risk-mitigation expectations, including disciplined cost caps, scope flexibility where feasible, and clear recognition of CAISO’s ability to rescope, defer, or cancel the project if underlying resource assumptions do not materialize. Such safeguards are essential to ensure that approval today does not translate into undue ratepayer risk tomorrow. Some of recently approved project sponsor agreements (APSA) have required specific cost containment mechanisms. For example, the CAISO is imposing a pre-condition on the approved project sponsor executing an APSA, that the approved project sponsor must agree that no major project costs on the project can be incurred without the express written approval of the CAISO, helping mitigate the abandoned plant cost risk.[5] BAMx believes that additional stricter cost containment provisions are warranted in the APSA for the proposed project that would allow the CAISO to revisit the need for the project in light of substantial and material regulatory and/or market conditions.

[1] Appendix F of the Draft Plan, p. 62.

[2] Id.

[3] CAISO’s April 15^th Presentation, p. 92.

[4] Draft Plan, p.10.

[5] “New Humboldt to Fern Road 500 kV Line Project” Project Sponsor Selection Report, June 2, 2025, p.82.

3. Please provide your organization’s comments on the Economic Assessment.

Please provide cost breakdown details for the Gates – Los Banos #3 500 kV Line Series Compensation project recommended for approval.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

 No comments at this time.

5. Please provide your organization’s comments on Frequency Response.

 No comments at this time.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. Need to Fully Understand the TAC Impact of the Recommended Transmission Projects

The Draft Plan does not include an estimate of future High Voltage Transmission Access Charge (HV TAC) rate impacts. BAMx appreciates that the CAISO is currently in the process of updating the “starting point” for the HV TAC estimating tool to January 1, 2025, and is targeting updating these results for inclusion in the revised draft transmission plan to be presented to the CAISO Board of Governors in May 2026.[1] BAMx used the CAISO 2024-2025 TAC estimate calculation to determine that the  nearly $5 billion in high-voltage transmission projects the CAISO is considering for approval in the current TPP cycle out of overall $7 billion, would increase the CAISO-wide HV TAC by about $3/MWh by the 2035-2036 timeframe.

As shown in the figure below, the transmission cost associated with the approvals in the last five (5) planning cycles (average of $5,408 million) since 2021-2022 TPP are substantially higher than the earlier nine (9) planning cycles since 2012-2013 TPP (average of $643 million). BAMx fully appreciates that the more recent project approvals are driven by increased load growth including building and transportation electrification, manufacturing, and large loads including data centers, and the state’s policy goals. However, the sky-rocketing TAC rates also reinforces the need to avoid excessive and unneeded transmission upgrades and to closely monitor and control costs, once the transmission upgrades are approved.

* Note the removal of the Serrano–Del Amo–Mesa 500 kV Transmission Reinforcement project ($1.125 billion) from the 2022-2023 TPP, as it is proposed for cancellation in the Draft 2025-2026 Transmission Plan.

[1] Draft Plan, p.173.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

The California Community Choice Association (CalCCA) applauds the California Independent System Operator (CAISO) for its efforts to develop the 2025-2026 Transmission Plan. Transmission is the key to unlocking additional generating capacity that is critically needed to support the clean energy transition. It is also necessary to ensure that new and existing load can be served in a reliable manner.

CalCCA’s comments on the Transmission Planning Process (TPP) are included below in Section 6. 

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

Please see section 6.

3. Please provide your organization’s comments on the Economic Assessment.

Please see section 6.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

Please see section 6.

5. Please provide your organization’s comments on Frequency Response.

Please see section 6.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

CalCCA recommends the CAISO make the following enhancements to the TPP:

• Reserved Transmission Plan Deliverability (TPD) Release Process: The CAISO proposes to reserve deliverability for geothermal, offshore wind, out-of-state (OOS) wind, and non-battery long-duration energy storage resources in the quantities and locations included in the 2035 base portfolios. A reservation process is necessary to allocate deliverability to long-lead time (LLT) resources that have longer project development cycles that extend beyond the cycle for TPD allocations to non-LLT resources. Reservations of deliverability for LLT resources, however, limit the amount of deliverability available to allocate to other resources that may be commercially viable and contracted for to meet policy and reliability objectives. The California Public Utilities Commission (CPUC) portfolios are developed using assumptions about technology availability and cost. To the extent these assumptions change, procured resources may differ from the portfolios. The CAISO should ensure that its process for releasing reserved TPD considers the local regulatory authorities’ planning assumptions and actual investments in new capacity and development milestones of contracted resources. This process should take place annually within the TPP to ensure reservations continue to reflect actual resource procurement and development.

• Maximum Import Capability (MIC) Enhancements: CalCCA appreciates the CAISO conducting the maximum import capability (MIC) expansion process to facilitate the contracting of imports necessary to support long-term policy needs. However, the MIC expansion process, and other elements of the MIC process, may be insufficient to provide load serving entities (LSE) and developers the certainty necessary to move forward with long-term procurement activities that support the amount of imports projected in the CPUC portfolios. As stated in CalCCA’s December 5, 2025, Comments,[1] the process for expanding MIC through upgrades should account for both local regulatory authority (LRA) planning assumptions and actual investments and development milestones of contracted out-of-state resources.  This is conceptually similar to the way in which transmission development is conducted for resources interconnecting to the CAISO grid in which: (1) the TPP has the benefit of the CPUC portfolios; and (2) the Generator Interconnection Process reviews resource needs, available queued projects, and commercial interest to develop transmission needed for deliverability. In addition, the CAISO should prioritize the MIC enhancements initiative submitted in the 2026 catalog process to explore ways to support the availability and certainty of MIC.[2]

• Stranded Cost Prevention for Data Center Driven Upgrades: A significant portion of TPP upgrades is being driven by load growth, including significant forecasted growth from data centers. Load growth from data centers is very uncertain at this time, meaning that there is a risk of stranded costs if the CAISO invests in infrastructure upgrades for load that does not materialize. When evaluating transmission solutions to support data center load growth, the CAISO should seek to minimize risk of stranded costs by identifying upgrades that support data center load growth and provide other policy, reliability, or economic benefits where possible.

Further, many of the upgrades are substantial and resemble area supply or reliability reinforcements, creating potential ambiguity around long-term cost responsibility absent clear guardrails. This risk is heightened because many of the upgrades are below 200 kV, meaning that any reclassification out of the load-interconnection framework could disproportionately burden TAC customers rather than being spread across the ISO system. The Joint CCAs also note that final cost allocation remains unsettled pending issuance of the CPUC’s final Rule 30 decision. Advancing a large portfolio of load-driven upgrades ahead of that decision increases the risk of misalignment between transmission planning outcomes and ultimate cost-responsibility rules.

• TPD Scarcity: CalCCA appreciates the CAISO’s efforts to identify policy driven upgrades to support the development of new clean resources. CalCCA is concerned that existing TPD is scarce and new TPD associated with policy approvals in this TPP may severely limit the amount of Cluster 16 projects that can enter the interconnection queue. The CAISO and CPUC should work together to ensure the policy portfolios result in sufficient TPD to support reliability and policy objectives with new deliverable capacity. 
•  
• OOS Wind: The CPUC portfolios include a significant amount of OOS wind. CAISO has signaled that, to its knowledge, there is limited OOS transmission development identified to support delivery of these projects to California. CalCCA supports the CAISO’s proposed Request for Information (RFI) to investigate whether the amount of OOS resources in the portfolio is realistic. If these projects do not materialize in sufficient volumes, the CPUC and CAISO will need to refine its portfolio development and resulting transmission planning to ensure state requirements can continue to be met.  

[1]            See CalCCA Comments on Policy & Economic Preliminary Assessment and Study Updates (Dec. 5, 2025), https://stakeholdercenter.caiso.com/Comments/AllComments/8dedac49-35a3-4164-96aa-f620710b1a18#org-78bbd38a-c496-43a8-9140-b07f4ff11739.

[2]      See Joint Parties Comments on Catalog Submissions – 2026 Market Policy Catalog and Roadmap Process (Mar. 2, 2026), https://stakeholdercenter.caiso.com/Comments/AllComments/04c6df24-b13b-4e59-b83b-7dd99085b4ef#org-85e61823-658d-40e8-9bfe-16753fbfe6cb.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

Introduction

The California Public Utilities Commission’s Integrated Resource Planning (IRP) process seeks to ensure that Load Serving Entities in the CPUC’s jurisdiction meet targets that allow the electricity sector to contribute to California’s economy-wide greenhouse gas emissions reductions at least cost, while maintaining electric service reliability and meeting other statutorily mandated state policy targets established in Senate Bill (SB) 350 (De León, 2015), Senate Bill (SB) 100 (De León, 2018), Senate Bill (SB) 1020 (Laird, 2022) and Assembly Bill (AB) 1279 (Muratsuchi, 2022). 

A key aspect of IRP and infrastructure development in the state is the robust coordination between the CPUC, which develops portfolios of future generation and storage resources over 10- and 15-year planning horizon, the California Energy Commission (CEC), which provides demand forecasts, and the CAISO, which identifies the transmission implications resulting from these resource portfolios and load forecasts. 

CPUC Staff appreciate CAISO’s work on this 2025-2026 Draft Transmission Plan, as well as the collaborative efforts throughout this TPP cycle. Ongoing interagency coordination to tighten linkages between transmission planning and the development and interconnection of new, cost-effective resources remains integral to meeting California’s clean energy goals.

Reliability-driven Projects

CPUC Staff recognizes the significant transmission build-out driven largely by expected load growth, especially in the Bay Area.  We appreciate CAISO’s consideration of multiple alternatives, including grid-enhancing technologies, to identify the most efficient solution to meet reliability requirements. The explanations for recommending utilization of high-capacity conductors on some projects (like the Tesla – Trimble – Metcalf 230 kV Corridor Expansion) but not for other projects is especially helpful.  

We note that the Draft Transmission Plan anticipates that “the steadily increasing load growth being identified in the Greater Bay area suggests additional capacity may be required in future planning cycles.”

Given this trend, CPUC Staff suggests CAISO continue to coordinate with CPUC on large loads and that future TPP cycles include a deeper analysis of how large load additions impact the sizing of components for CAISO-recommended transmission projects.

CPUC Staff supports CAISO’s recommendation to cancel the previously approved Serrano-Del Amo-Mesa 500 kV Transmission Reinforcement project, as well as the Helm 230/70 kV Bank project, due to significantly higher cost estimates resulting from increased requirements identified in the detailed engineering phase.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

CPUC Staff notes the continuation of a trend observed in prior TPP cycles: there is a smaller number (4) of policy-driven transmission projects relative to the number (33) of reliability driven projects.  Given that the CPUC provided TPP base portfolio analyzed by CAISO for this TPP cycle includes over 100 GW additional capacity by 2040 (beyond existing under-development resources), CAISO’s recommendation for only four policy-driven projects demonstrates that coordinated state efforts to map expected resources to transmission zones with available capacity are working well to use the existing system efficiently, in concert with the already approved policy driven projects in prior cycles. More resources do not necessarily mean more transmission investment when coordinated planning focuses on efficient use of the existing (and already underway) grid.     

An additional factor that may have contributed to fewer policy-driven projects than expected, given the number of transmission exceedances identified in the CPUC’s busbar mapping, is the addition of resources that CAISO includes in its analysis. Nearly 2.8 GW of storage were added by CAISO to the resource portfolios to reflect resources that came online and entered development after the CPUC’s transmittal of portfolios in Decision (D.) 25-02-026 or were added from utilities that are not CPUC-jurisdictional, perhaps mitigating the need for new transmission.

CAISO’s TPP analysis includes “unaccounted-for Transmission Plan Deliverability” (TPD) — capacity that has been awarded TPD by the CAISO but does not match resources in the CPUC portfolio baseline at the relevant points of interconnection — while the CPUC’s busbar mapping does not. CPUC Staff has discussed this gap with CAISO and, as noted on page 93 in D.26-02-057 (which conveyed the CPUC portfolios for the 2026-2027 TPP cycle), “Commission staff will continue to work with the CAISO to further refine a standardized policy and methodology for considering unaccounted-for TPD in busbar mapping, as feasible.”

CPUC Staff look forward to continued work with CAISO staff on cost-effectively addressing local reliability, and to better understand the local procurement-related matters discussed in the April 15, 2026, stakeholder meeting.

Finally, CPUC Staff anticipated and supports CAISO’s recommendation on the Trout Canyon – Lugo 500 kV Line, the largest policy-driven project in this Draft Transmission Plan. This project is expected to support the delivery of key out-of-state wind and geothermal resources identified in IRP portfolios.

3. Please provide your organization’s comments on the Economic Assessment.

CPUC Staff commend CAISO on proactively identifying the congestion impacts along the Path 15 Corridor and thoroughly evaluating 19 potential solutions. Furthermore, we applaud refinements to the TEAM methodology to better capture the value of congestion relief in a changing market context. CPUC Staff supports the proposed 70% series compensation on the Gates – Los Banos #3 500 kV line as a least-regrets economic-driven upgrade.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

CPUC Staff have no comments at this time.

5. Please provide your organization’s comments on Frequency Response.

CPUC Staff have no comments at this time.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

IRP Portfolios for the 2025-2026 TPP

CPUC staff would also like to provide broad comments on the Draft Transmission Plan. This annual TPP assessment by the CAISO utilized the portfolio of generation and storage resources that was adopted by the Commission in D.25-02-026, which optimizes clean energy resource procurement to reach GHG emissions reduction targets while continuing to maintain system reliability. Specifically, the CPUC’s  25-26 TPP base case portfolio included over 70 GW of new clean generation and storage resources to cost-effectively achieve a 25 million metric ton GHG emissions level by 2035, while maintaining system reliability at the lowest cost to ratepayers. 

Notably, this portfolio includes in aggregate the individual Integrated Resource Plans (IRPs) of all Load Serving Entities (LSEs) to develop the base portfolio, reflecting the resource preferences of those LSEs through 2035. CPUC Staff augmented these resources using modeling analysis to develop a portfolio that meets reliability standards and GHG reductions targets through 2040.

The CPUC also transmitted a sensitivity portfolio to CAISO to help understand the transmission implications of a portfolio with a greater volume of long lead-time (LLT) resources. This portfolio reflects the resource types online,  under contract identified in LSE plans, with amounts and types similar to the those included in D.24-08-064 pursuant to Assembly Bill (AB) 1373 (Garcia, 2023), while also including the LSE planned resources as submitted in November 2022 only through 2030. This sensitivity analysis will help the state better analyze the transmission development that could be needed for a portfolio  reflecting the maximum amount and types of LLT resources included in D.24-08-064.

IRP Process Develops Least Cost Portfolio that Considers Expected Transmission Costs

As explained in CAISO’s presentation (slide 11) at the April 15, 2026, stakeholder meeting, the CPUC’s resource portfolio and the CEC’s demand assumptions are the key inputs driving the transmission infrastructure that CAISO staff has identified for development within the 2025-2026 Draft Transmission Plan. Importantly, the CPUC’s modeling that developed this base case portfolio selects optimal resources based on several factors, including capital costs of new resources and costs associated with transmission that might be needed to support these resources.  Thus, CAISO’s analysis and the resulting identification of transmission projects needed to accommodate this ongoing build-out of clean energy and storage resources represent a cost-effective path toward to meeting the state’s goals by 2045. 

IRP Process Contributes to Efficient Transmission Build-out

This draft Transmission Plan identifies need for 33 reliability-driven transmission projects with an estimated cost of $4.4 billion, explaining that “reliability projects driven by load growth and evolving grid conditions as the generation fleet transitions to increased renewable generation … [transmission] projects are required to reliably meet the increase in forecasted load related to electrification, large loads such as data centers and electric vehicle transportation loads.” In contrast, the draft Plan identifies four policy-driven transmission projects, with an estimated $2.4 billion cost.

CPUC Staff also notes that the base case portfolios that the CPUC has transmitted to the CAISO to analyze over the past three TPP cycles have remained fairly consistent in policy targets. Thus, many transmission needs in the 2025-2026 base case are already addressed by upgrades approved in previous TPP cycles.  This aligns with the Commission’s Decision (D.) 23-02-040 which encouraged this head start to mitigate longer development lead-times for major transmission projects. 

The coordination between state agencies and the CAISO includes in the process documented in the CPUC’s busbar mapping methodology, which involves a working group comprised of CPUC, CAISO, and CEC staff mapping expected resources to areas with current or future transmission capacity, as CAISO’s TPP identifies, to minimize overall costs to ratepayers. The methodology has also been developed with considerable stakeholder input.

CPUC staff will continue to work with CAISO staff to continually refine this integrated planning approach to support the development of the necessary clean electricity infrastructure needed to continue maintaining system reliability, meet state climate goals, and serve all electric customers.  

Large Load Project Concurrences

CPUC Staff note that CAISO has issued ‘concurrences’ for six network upgrades intended to support PG&E large load interconnections / energizations.  CPUC understands from the Draft Transmission Plan that in issuing a concurrence, rather than approval, CAISO is affirming that the identified upgrades meet reliability requirements and are consistent with long-term transmission plans in the area(s).  The CPUC understands that a concurrence is not an approval and does not represent the position that the identified upgrades serve to benefit the greater grid.

This distinction is important because the scope of Application (A.) 24-11-007 (PG&E’s pending Rule 30 Application) includes cost causation, cost allocation, jurisdictional treatment, cost recovery refunds, prefunding, and stranded-cost protections for the facilities needed to energize large-load retail customers at the transmission level, including transmission network upgrades. The CPUC can foresee that these concurrences may introduce ambiguity regarding which network upgrades are approved by the CAISO as benefiting the overall grid, and which are caused by specific large load customers seeking energization.  The CPUC recommends additional clarifying language to further distinguish TPP approvals from concurrences, does not consider a concurrence to be CAISO approval of a network upgrade, and continues to expect PG&E to include such network upgrades as components of their transmission-level energization filings at the CPUC.

Absence of Impacts on the Transmission Access Charge

As has been the case for at least a decade, CAISO has not provided information in Section 8.3 (Capital Program Impacts on Transmission High-Voltage Access Charge) in the Draft Transmission Plan.  This section is important for Stakeholders to understand an estimate of future High Voltage TAC rates resulting from the Projects approved in the TPP.  CAISO notes that it is “in the process of updating the ‘starting point’ for the HV TAC estimating tool,” and that results would be included in the Revised Draft Transmission Plan, which is typically published only two weeks before the Board of Governors' approval in May.

To enable Stakeholders to understand and comment on cost impacts, the CPUC requests that, in the future, CAISO include this important information related to impacts on the High Voltage TAC in its Draft Transmission Plans.

Summarizing Comments

Overall, CPUC staff greatly appreciate CAISO’s efforts to produce this comprehensive transmission analysis, which is key for maintaining system reliability and achieving the state’s clean energy goals. We especially appreciate the focus on minimizing ratepayer impacts through CAISO’s comprehensive evaluation of alternatives, the cancellation of previously approved projects that had grown too costly, the utilization of storage resources to mitigate transmission needs and, finally, CAISO’s recognition that increased Path 15 congestion warrants economic-driven transmission.

Regarding concurrences of transmission network upgrades related to large load energization, the CPUC requests clarification that these do not constitute CAISO approvals but are simply acknowledgment that these projects are not inconsistent with the grid’s reliability needs.  Finally, the CPUC requests that the CAISO work to include the impacts of approved projects on the High Voltage TAC in earlier drafts of the Transmission Plan.   

We largely support this 2025-2026 Draft Transmission Plan in which CAISO has identified the transmission buildout currently needed to reliably integrate the resource mix that will keep the state on the optimal and most cost-effective pathway to meet established state goals.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

The Public Advocates Office at the California Public Utilities Commission (Cal Advocates) provides these comments on the California Independent System Operator’s (CAISO) 2025-2026 Transmission Planning Process (TPP) – Draft Transmission Plan (Draft Plan), and April 15, 2026 stakeholder meeting.  Cal Advocates is an independent ratepayer advocate with a statutory mandate to obtain the lowest possible rates for utility services, consistent with reliable and safe service levels and the state’s environmental goals.[1]

1. CAISO’s Proposed Project Approvals and Concurrences Should Consider California’s Skyrocketing Electric Rates.

California is in a rates crisis, with the second highest electricity rates in the country.[2]  The Draft Plan recommends approval of $7.0 billion in new transmission capital expenditures (e.g., transmission network upgrades and local network upgrades).[3]  Additionally, CAISO concurs with PG&E as to $1.9 billion in local network upgrades to interconnect 11 data centers.[4] These upgrades amount to an additional $8.9 billion in total project costs.  Previous TPPs approved costs of $7.3 billion,[5] $6.1 billion,[6] and $4.8 billion[7] between 2023 and 2025, respectively, totaling $27.1 billion in TPP approved costs in the last 4 years. The four most recent TPPs average more than 9 times the yearly average of the previous 22 years.[8] This staggering financial commitment to transmission infrastructure is unsustainable and could result in an increase of the High-Voltage Transmission Access Charge (HV TAC) from its current rate of $15.75/MWh to $24.03/MWh by 2036.[9]  

Accordingly, Cal Advocates recommends that CAISO continue to (1) re-evaluate previously approved projects for necessity, (2) ensure that approved projects are the most cost-effective, and (3) consider low-cost grid enhancing technologies (GETs), where feasible.  Cal Advocates is encouraged by CAISO’s cancelling or placing on hold three previously approved projects due to extreme cost increases.[10] For example, CAISO canceled the Del Amo - Mesa - Serrano 500 kV project, the cost of which increased from $1.125 billion to $5.0 billion.  The CAISO should complete thorough reviews and analysis to ensure the most cost-effective alternative is selected, while re-evaluating and, where appropriate, eliminating costly and unnecessary projects.

2. Utilities Treat Concurrence the Same as CAISO Approval and the Costs of Concurrence Projects should be Reflected in the Draft Plan Totals.

The Draft Plan recommends approval for $7.0 billion in new transmission capital expenditures[11] and concurs with $1.9 billion in data center network upgrades,[12]^{, [13]} for a total $8.9 billion in project costs. The utilities often treat CAISO project concurrences the same as a CAISO approval.  For example, in a recent hearing considering a new large-load interconnection tariff (Rule 30 proceeding) at the California Public Utilities Commission (CPUC), Pacific Gas and Electric Company (PG&E) stated that “CAISO concurrence allows us to proceed forward.”[14]  For improved transparency on the impacts to ratepayers, the Draft Plan should reflect that it is approving $8.9 billion in transmission network upgrades and concurred local network upgrades, rather than the $7.0 billion described in the plan.   

3. To Protect Ratepayers, CAISO Should Require Signed Interconnection Agreements as a Condition for CAISO Concurrence of Data Center Interconnection Projects.

In the Draft Plan, CAISO concurs with PG&E proposed upgrades to interconnect numerous data centers, totaling $1.9 billion.[15]  This constitutes an outsized addition to an already costly transmission plan, further impacting the TAC.  However, PG&E has yet to demonstrate that these customers have fully committed to interconnecting with Signed Agreements.  

PG&E submits applications to CAISO after customers sign off on an Engineering Study.  The Engineering Study is a step in PG&E’s interconnection process to get to the final Signed Agreement for Electric Service.[16]  Unlike when an applicant cancels a data center project after a Signed Agreement, applicants can withdraw their application after the Engineering Study or after its application is submitted to CAISO, without penalty.[17]  On the other hand, customers with Signed Agreements have agreed to a payment schedule and are financially obligated to pay their initial advance.[18]  Thus, customers with a Signed Agreement, compared to an Engineering Study, demonstrate a higher commitment to bring load to the system and use the facilities CAISO approves or concurs with.

PG&E failed to demonstrate that the customers it proposed to CAISO have Signed Agreements.  However, with CAISO’s concurrence, PG&E would have the go ahead to build transmission projects, regardless of whether the customer’s load comes online.[19]  CAISO should provide its concurrence for any required transmission projects only after PG&E demonstrates a customer’s commitment to interconnect through a Signed Agreement.

4. CAISO and PG&E Should Explain the $68 Million Increase for the Concurred Project to Interconnect LC24-3.

At the September 25, 2025 Stakeholder meeting, PG&E presented the scope for projects studied in PG&E’s 2024 Cluster Study.  In the Draft Plan, the scope of an unnamed project increased by $68 million without explanation.  CAISO should explain why this project has changed scope and what the details of the project change include to justify the $68 million cost increase.

At the September meeting, the project to support the interconnection of LC24-3 included the following scope items.

• Interconnection:
  • Build new 115 kV switching station, Charcot, near Trimble 115 kV and associated service lines.
  • Build (2) 0.8-mile 115 kV transmission line to connect Charcot to Trimble 115 kV.
• Capacity Upgrade:
  • Trimble 230 kV/115 kV Substation expansion looping onto NRS-San Jose B 230 kV Line.[20]

In the Draft Plan, the scope now includes an additional item under Capacity Upgrades, without any discussion of the change: Trimble-Montague 115 kV line upgrade.[21]  This change increases the cost from $242 million - $484 million to $276 million - $552 million.  Further, this project now references five other large loads to be supported by this project, even though these large loads are already supported by other projects in the Cluster Study.  Cal Advocates recommends that CAISO and PG&E clarify why this item was added to the scope, explain which data centers rely on the project, provide the details of the project change, and justify the $34 million - $68 million increase in cost.

5. CAISO Should Include the Draft Plan Impacts on the High-Voltage Transmission Access Charge (HV TAC) for Transparency and Due Process.

CAISO’s Draft Plan does not include analysis of cost impacts of the Draft Plan to HV TAC rates.[22]  This has been a recurring problem in the last four TPP cycles.[23]  CAISO’s HV TAC analysis provides critical cost information necessary to fully evaluate the impact of the Draft Plan on transmission rates.  Failing to include the HV TAC analysis reduces transparency and denies stakeholders the ability to analyze and vet the cost impacts of CAISO’s proposed plan.  Given California’s ongoing electric rates crisis, it is critical that stakeholders have the opportunity to provide feedback on this analysis.  To improve transparency and to provide due process, CAISO should expeditiously post its 2025-2026 HV TAC forecasts and include HV TAC estimates in all future draft TPP plans.

Cal Advocates analyzed CAISO’s 2024-2025 HV TAC model, and added the capital expenditures proposed in the Draft Plan to estimate the potential HV TAC impact in lieu of an analysis in the Draft Plan.  The model forecasts that the HV TAC rate will rise to $24.03/MWh by 2036, compared to the current HV TAC rate of $15.75/MWh.[24]^{, [25]}  This change amounts to a 53% increase in the HV TAC over 10 years.  Further, $2.89/MWh, or 35% of the HV TAC increase, is attributed to projects recommended for approval in this year’s Draft Plan alone.  This increase will further exacerbate the current electric rates crisis.  Notably, this analysis excludes the $1.9 billion in CAISO concurred data center interconnection projects, which will additionally impact transmission rates.

6. CAISO and the Participating Transmission Owners Should Provide Details on the Costs to Integrate New Data Center Loads.

CAISO and the Participating Transmission Owners (PTOs) do not provide the cost impacts for the different drivers of new transmission investments in the TPP.   As a result, the cost impacts associated with accommodating new data center demand are undistinguishable from other loads.  CAISO should identify all projects that are primarily driven by the data center loads in the Draft Plan.  Only one project recommended for approval in the $9 Billion Draft Plan references data center load as a driver,[26] although it is likely that many other projects that cite load growth in the Greater Bay Area share this project driver.  To increase transparency, Cal Advocates recommends that CAISO and its PTOs identify the data center-driven transmission costs in the 2025-2026 TPP.  This will enable stakeholders to properly evaluate the impact of integrating data center loads.  Demands to integrate these new types of data centers started increasing in 2022, and state and federal policies to respond to the impact of these new types of data centers on grid reliability and potential cost shifts are still being formulated.[27]^{, [28], [29]}  New California and federal policies may require new data centers to pay their share of new transmission investments -- making it imperative that CAISO identify data center driven transmission costs.

Cal Advocates also recommends that the CAISO 2025-2026 TPP identify any new transmission investments that would be unnecessary if not for new data center load.  This will enable stakeholders to understand the impacts of data center loads on the transmission system and points to specific projects that could be canceled, reduced, or modified if the data center load does not materialize.

7. CAISO and its PTOs Should Provide Itemized Project Cost Estimates and the Length of Proposed New and Reconductored Lines for All Proposed Projects.

In the Draft Plan, CAISO does not provide information on the cost for individual project components or consistently provide the length of new and reconductored lines.  These deficiencies obscure the cost of individual project scope items.  Without this information, it is difficult for stakeholders to compare the proposed project descriptions to PTO cost benchmarks to confirm whether the project costs estimates are reasonable.  

For example, projects with similar scopes may have very different costs.  The Monta Vista 230/115 kV Transformer Bank Addition and San Jose B 230/115 kV Transformer Bank Addition projects both install one 230/115 kV transformer bank and have cost ranges of $52 million - $104 million and $35 million - $70 million, respectively.[30]  This cost difference cannot be discerned from the Draft Plan and PTO Per Unit Cost Guides.  Further, projects that do not include line lengths cannot be checked using the PTO Per Unit Cost Guides.  Neither the Lincoln – Pleasant Grove Line Reconductoring Project nor the TL623C Reconductor project includes line lengths in the transmission plan.

Federal Energy Regulatory Commission (FERC) Order No. 890 and the proceeding transmission planning Order No. 1000-A require that transmission providers provide sufficient details in their regional transmission planning process to allow one to replicate the results of the planning study.[31]^{, [32]}

To comply with the FERC Orders No. 890 and 1000-A’s openness and transparency transmission planning principles, Cal Advocates recommends that CAISO include the costs for each component and the approximate length of new transmission lines or reconducted lines for every proposed project in the Draft Plan.

8. Southern California Edison (SCE) Should Include Reconductoring Cost Estimates in the Per Unit Cost Guide.

SCE’s Per Unit Cost Guide does not include a cost estimate for reconductoring, which makes it difficult to determine whether the cost of the Mesa - Laguna Bell 230 kV #2 Upgrade (Advanced Reconductoring) is reasonable.  Cal Advocates recommends that SCE’s costs for reconductoring be included in the Draft Plan, as well as be updated in SCE’s Per Unit Cost Guide.

[1] Cal. Pub. Util. Code § 309.5.

[2] Californians pay second highest electricity rates in the country, according to a new report, Megan Myscofski, January 9, 2025, available at https://www.capradio.org/articles/2025/01/09/californians-pay-second-highest-electricity-rates-in-the-country-according-to-a-new-report/.

[3] CAISO Draft 2025-2026 Transmission Plan at 5.

[4] CAISO Draft 2025-2026 Transmission Plan at 92-94.

[5] CAISO 2022-2023 Transmission Plan at 3.

[6] CAISO 2023-2024 Transmission Plan at 3.

[7] CAISO 2024-2025 Transmission Plan at 7.

[8] Cal Advocates Transmission Data Dashboard at 3, available at https://www.publicadvocates.cpuc.ca.gov/press-room/reports-and-analyses/transmission-data-dashboard-2025.

[9] See section 5 for analysis.

[10] Southern California Edison (SCE) informed CAISO that the cost of the Coolwater 115 kV Line Looping into Tortilla 115 kV Substation project has increased from $37 million to $105 million.  Further, the load in the area has decreased.  This project is now on hold.  CAISO Draft 2025-2026 Transmission Plan at 90.

SCE informed CAISO that the cost of the Julian Hind-Mirage 230 kV Line Upgrade Project has increased from $76 million to $178 million.  Further, the amount of Department of Energy (DOE) subsidization is still being evaluated.  This project is now on hold.  CAISO Draft 2025-2026 Transmission Plan at 89.

SCE informed CAISO that the cost of the Del Amo - Mesa - Serrano 500 kV project has increased from $1.125 billion to $5.0 billion.  This project is now canceled.  CAISO Draft 2025-2026 Transmission Plan at 109.

[11] CAISO Draft 2025-2026 Transmission Plan at 5.

[12] CAISO Draft 2025-2026 Transmission Plan at 92-94.

[13] To address a new large load interconnection request that comes in after development of the demand forecast and CPUC resource portfolios, Participating TOs may submit proposals into the ISO’s Transmission Planning Process for the ISO’s concurrence in the Transmission Plan.  Large Load Considerations Issue Paper, CAISO, January 30, 2026 at 9.

[14] Reporter’s Transcript, Evidentiary Hearing, A.24-11-007, April 15, 2026 at 523, lines 9-10.

[15] CAISO Draft 2025-2026 Transmission Plan at 92-94.

[16] Comments on the December 17, 2025 California Energy Commission (CEC) Integrated Energy Policy Report (IEPR) Commissioner Workshop on Energy Demand Forecast Results, Cal Advocates, December 31, 2026, available at https://www.energy.ca.gov/event/workshop/2025-12/iepr-commissioner-workshop-energy-demand-forecast-results.

[17] Data center applicants can cancel or withdraw its data center project without penalty prior to signing binding interconnection agreements with the utility.  An Engineering Study is not the same thing as a binding interconnection agreement.  An Engineering Study is part of the process that leads up to the signing of binding interconnection agreement(s).  Comments on the December 17, 2025 California Energy Commission (CEC) Integrated Energy Policy Report (IEPR) Commissioner Workshop on Energy Demand Forecast Results, Cal Advocates, December 31, 2026, available at https://www.energy.ca.gov/event/workshop/2025-12/iepr-commissioner-workshop-energy-demand-forecast-results.

[18] Comments on the December 17, 2025 California Energy Commission (CEC) Integrated Energy Policy Report (IEPR) Commissioner Workshop on Energy Demand Forecast Results, Cal Advocates, December 31, 2026, available at https://www.energy.ca.gov/event/workshop/2025-12/iepr-commissioner-workshop-energy-demand-forecast-results.

[19] Reporter’s Transcript, Evidentiary Hearing, A.24-11-007, April 15, 2026, at 523, lines 9-10. (PG&E witness describing that “the CAISO concurrence allows us to proceed forward.”)

[20] CAISO 2025-2026 Transmission Planning Process, September 25, 2025, PG&E Presentation at 63.

[21] CAISO Draft 2025-2026 Transmission Plan at 93.

[22] CAISO Draft 2025-2026 Transmission Plan at 173.

[23] Only the previous four draft transmission plans were checked.  See CAISO Draft 2024-2025 Transmission Plan at 194; CAISO Draft 2023-2024 Transmission Plan at 161; CAISO Draft 2022-2023 Transmission Plan at 170; CAISO Draft 2021-2022 Transmission Plan at 382.

[24] High Voltage Access Charge Rates Effective Jan 30, 2026 (Revised Apr 8, 2026), CAISO, April 10, 2026, available at high-voltage-access-charge-rates-effective-jan-30-2026-revised-apr-08-2026.pdf.

[25] The starting point was not updated in CAISO’s 2024-2025 HV TAC model to the current HV TAC ($15.75/MWh).  The actual TAC rate in 2036 may be higher.

[26] San Jose B 230/115 kV Transformer Bank Addition project refers to data center load specifically.  CAISO Draft 2025-2026 Transmission Plan at 61.

[27] Department of Energy (DOE) Advanced Notice of Proposed Rulemaking (ANOPR), Interconnection of Large Loads to the Interstate Transmission System (FERC Docket No. RM26-4-000), October 23, 2025.

[28] Ratepayer Protection Pledge, March 4, 2026, available at https://www.whitehouse.gov/releases/2026/03/ratepayer-protection-pledge/.

[29] PG&E Rule 30 Application (CPUC Application Number: A.24-11-007), November 21, 2024.

[30] CAISO Draft 2025-2026 Transmission Plan at 56 and 61.

[31] Order No. 890, FERC Stats. & Regs. ¶ 31, 241 item 471 at 269-270.

[32] Order No. 1000-A, FERC Stats. & Regs. ¶ 61,132, item 281 at 211.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

1. Cal Advocates Recommends Ratepayer Protections in the Competitive Solicitation Process and Continued CAISO Evaluation of the Trout Canyon – Lugo 500 kV Line.

CAISO recommends approval of the Trout Canyon – Lugo 500 kV Line in the Draft Plan.  This is the most expensive project in the Draft Plan.  CAISO estimates the cost to be $1.3 billion - $1.8 billion.[1]  This policy-driven project intends to help enable the delivery of out-of-state wind resources and is eligible for competitive solicitation.  Recent uncertainty in large wind projects increases the likelihood of this project being unable to fulfil its expected role.[2]  CAISO should maintain the ability to cancel, reduce, or modify the project if the intended resources fail to materialize.

Cal Advocates recommends that CAISO continue to monitor this project’s need and feasibility.  If the out-of-state resources do not materialize as expected, ratepayers will be paying for a massive, stranded asset.  Further, Cal Advocates recommends that CAISO insert provisions into the competitive solicitation process that allow for flexibility based on need and feasibility.  CAISO should maintain the ability to cancel, reduce, or modify the project if the intended generation resources fail to materialize.  In this way, ratepayers will be protected if CAISO decides to alter the Trout Canyon – Lugo 500kV Line in the future.

[1] CAISO Draft 2025-2026 Transmission Plan at 108.

[2] Exclusive: Wind projects pile up as Pentagon reviews stall, Amy Harder, March 30, 2026, available at https://www.axios.com/2026/03/30/trump-war-department-wind-projects-pentagon.

3. Please provide your organization’s comments on the Economic Assessment.

Cal Advocates has no comments on the Economic Assessment study results at this time.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

Cal Advocates has no comments on the Maximum Import Capability Expansion requests at this time.

5. Please provide your organization’s comments on Frequency Response.

Cal Advocates has no comments on the Frequency Response study results at this time.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. CAISO Should Review Concurred Projects in the Stakeholder Meeting.

CAISO did not provide stakeholders an opportunity to review the concurred projects in the April 15, 2026 Stakeholder meeting.  In the Draft Plan, CAISO concurs with PG&E as to $1.9 billion in local upgrades to interconnect 11 data centers.[1] This will increase the Draft Plan projects costs by 27%.[2]  This constitutes a significant addition to an already expensive transmission plan.  Stakeholders should have the opportunity to review concurred projects and ask questions about CAISO’s process for concurrence.  To improve transparency and to provide due process, Cal Advocates recommends that all future concurred projects be reviewed as part of the Draft Transmission Plan Stakeholder Meeting.

2. Cal Advocates Supports the Addition of IDs for CAISO-Approved Projects.

CAISO implements unique IDs for new and previously approved projects in the Draft Plan.  This will improve project tracking and transparency in the TPP, Transmission Development Forum, and Transmission Project Review.  Cal Advocates supports this addition by CAISO and encourages CAISO to continue this practice in all future TPPs.

CAISO should also assign IDs to concurred projects.  The concurred projects in the Draft Plan have no ID or name.  This makes it difficult to refer to specific concurred projects.  

[1] CAISO Draft 2025-2026 Transmission Plan at 92-94.

[2] $7.0 billion (Projects recommended for approval) + $1.9 billion (Project concurred for large load interconnections) = $8.9 billion.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

Cal Western has not comments on Reliability driven projects

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

Cal Western has no comments on Policy driven projects

3. Please provide your organization’s comments on the Economic Assessment.

California Western Grid Development LLC Comments

  On the April 7, 2026 Draft Plan in the 2025-2026 TPP    

April 27, 2026

California Western Grid Development LLC (“Cal Western” or” CWG”) hereby submits these comments on April 7, 2026, Draft Plan in the 2025-2026 TPP.  (“Draft Plan”).  CWG’s
Pacific Transmission Expansion Project (“PTE” or “PTEP”) has been studied in the 2025-2026 Transmission Planning Process as an economic transmission solution as well as a solution to reliability needs, and State Public Policy needs as part of CAISO’s Multi-Value Project (“MVP”) analysis.

Consistent with CWG’s past recommendations, the April 7^th Draft Plan contemplates a change in the TEAM methodology for evaluating congestion benefits in the 2026-27 TPP.  As shown on slide 106 of the CAISO presentation at the April 15, 2026 stakeholder meeting, in large part due to that one change, PTEP’s benefit to cost ratio (“BCR”) improved from 0.17 to 1.06, establishing that PTEP is an economic project.  In addition, the 2025-25 TPP draft study results indicate the LCR benefits for PTEP are likely to improve as the local reliability requirement for the LA Basin continues to grow.

Since the change in the TEAM methodology will be finalized and implemented, we respectfully request that PTEP be held-over and studied in the 2026-2027 TPP.

Respectfully submitted

Marty Walicki

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

Cal Western has no comments on MIC expansion requests

5. Please provide your organization’s comments on Frequency Response.

Cal Western has no comments on Frequency Response

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

No comment.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

As a result of CAISO’s drastic changes to the TPD allocation data and assumptions in SCE’s system, the proposed Trout Canyon-Lugo 500 kV transmission line will not be able to provide any deliverability capacity to projects in the SCE East of Pisgah study area that is needed to justify its cost of up to $1.8B.  (See April 15, 2026, Stakeholder Meeting Presentation at Slide 92.)  To provide sufficient policy value, CAISO should augment this plan with upgrades that enable on-peak delivery into load centers.

Prior to the recent updates to TPD data and assumptions, the Trout Canyon-Lugo upgrade would have provided deliverability capacity for thousands of megawatts of resources in CAISO’s EOP area.  However, CAISO’s recent modifications to its TPD allocation study data and assumptions* will prevent any project in EOP from getting deliverability.  To remedy this, CAISO should plan for additional upgrades from the Lugo substation to the Mesa substation, either directly or via the Mira Loma or Vincent substations.  Ideally, this should occur in the current TPP cycle.  At a minimum, CAISO should indicate that the companion deliverability upgrades will be planned in the next TPP cycle. Alternatively, the proposed Trout Canyon-Lugo upgrade could be held over and considered in the next cycle.

*The TPD allocation study is now based on the 2035 study year, which includes a very large load increase in the western SCE Metro study zone (LA Basin).

3. Please provide your organization’s comments on the Economic Assessment.

No comment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

No comment.

5. Please provide your organization’s comments on Frequency Response.

No comment.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

No comment.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

3. Please provide your organization’s comments on the Economic Assessment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

 No comment.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

 No comment.

3. Please provide your organization’s comments on the Economic Assessment.

Introduction: Citizens Energy Corporation (“Citizens”) submits these comments as both an existing Participating Transmission Owner (PTO) in the CAISO system[1], and a partner with Golden State Clean Energy (“GSCE”) in their Valley Clean Infrastructure Plan (“VCIP”) being developed with Westlands Water District (“WWD”).

Citizens is a non-profit energy company, founded by former Congressman Joseph P. Kennedy II, with a track record of providing over $600 million of charitable assistance since its founding in 1979. Citizens fulfills its charitable mission by investing in for-profit businesses and using the profits to fund various charitable activities. Since 2012, Citizens has pioneered a unique transmission investment business model that creates significant charitable assistance/community benefits for the communities that host the infrastructure – without adding to project costs. This is the role and value Citizens brings to the VCIP development team.

Comments: Citizens supports the draft 2025-2026 Transmission Plan and its recognition that additional transmission infrastructure is needed to access and deliver in-state renewable resources. The CAISO’s economic analysis and focus on the Path 15 corridor congestion highlights the need to find a solution to interconnecting solar and battery storage resources in the San Joaquin Valley. Citizens supports CAISO’s decision to conduct comprehensive bulk system impact studies and detailed engineering studies for the Path 15 corridor and the upstream and downstream systems, and to identify specific solution(s) in the next planning cycle.

The draft plan identifies significant annual Path 15 congestion costs of $1.8 billion by 2035.^[2] These costs exacerbate an already-critical affordability crisis and support the need to bring new Path 15 infrastructure in-service as soon as possible. Accordingly, the CAISO should seek transmission solutions with accelerated development and construction timelines, thus delivering real cost savings from faster congestion relief. VCIP is uniquely positioned to provide these benefits: expedited Path 15 infrastructure development, already certified Program Environmental Impact Report, WWD’s existing statutory authority to construct transmission within its footprint, and Citizens’ documented ability to provide significant community benefits without adding to project costs.  Citizens supports CAISO completing the engineering studies to identify comprehensive regional solutions, and then prioritizing solutions, like VCIP, that can be constructed quickly.

Citizens also agrees with the draft plans’ focus on the importance of a separate right of way for the proposed new 500 kV line in the San Joaquin Valley. Existing corridors, including the current Path 15 alignment, are already heavily utilized and constrained. Any new 500 kV infrastructure should be routed close to planned or permitted renewable resources in the San Joaquin Valley to avoid the need to develop lengthy, expensive, and difficult-to-site genties (needing to cross I-5 and active agricultural land). A new Path 15 corridor solution that integrates solar from the San Joaquin Valley will also complement California land use and environmental planning principles for low conflict land use.

Citizens believes VCIP is a uniquely effective solution to the Path 15 corridor congestion – it is cost-effective, enjoys an accelerated development and construction timeframe due to AB 2661 and the certified Program Environmental Impact Report, and has proactively begun to address the need to deliver significant community benefits through its partnership with Citizens.

[1] Citizens-Sunrise Transmission LLC, Citizens Sycamore-Penasquitos Transmission LLC, and Citizens S-Line Upgrade Transmission LLC

[2] CAISO, draft 2025-2026 Transmission Plan, at pg. 119 (Table 4-1), April 7, 2026.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

 No comment.

5. Please provide your organization’s comments on Frequency Response.

 No comment.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

Citizens appreciates the ISO’s stated coordination between the Transmission Planning Process and the Transmission Project Execution and Completion Process in addressing many of the significant barriers to transmission development[1]. Citizens’ unique transmission investment model has a track record of creating significant, sustained community benefits for the areas that host the projects (importantly, without adding incremental project costs), which significantly increases the likelihood of local buy-in and acceptance for the projects. As this has already proven to be an effective tool for Citizens and its partners for successful project execution and completion on three different occasions within the CAISO footprint, Citizens encourages the CAISO to prioritize projects that have proven strategies for delivering clear community benefits without adding to project costs.

Citizens Energy Corporation supports the draft 2025-2026 Transmission Plan and urges the CAISO Board to approve the draft plan.

[1] CAISO, draft 2025-2026 Transmission Plan, at pg. 34 (Section 1.6.5), April 7, 2026

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

The City of Palo Alto (“Palo Alto” hereafter) appreciates the opportunity to comment on the CAISO’s 2025-2026 Draft Transmission Plan posted on April 7, 2026, and the material presented at the CAISO Stakeholder meeting on April 15, 2026. 

1. Palo Alto Supports Revised Project Scope for New Ames Distribution–Palo Alto 115 kV
   
   Palo Alto appreciates CAISO’s continued focus on reliability needs in the Greater Bay Area and strongly supports the revised scope of the New Ames Distribution–Palo Alto 115 kV project included in the Draft 2025–2026 Transmission Plan. The revised scope incorporating advanced conductors capable of achieving a summer emergency rating of 3,000 amps or higher, as well as limited reconductoring of the existing Ames Distribution 115 kV line directly responds to reliability needs previously identified by CAISO and by Palo Alto in its October 2025 comments.[1] The enhanced capacity of this configuration materially strengthens the project’s ability to mitigate thermal overloads on the Cooley Landing #1 and Ravenswood–Palo Alto #1 and #2 115 kV facilities identified in CAISO’s reliability assessments.[2] Palo Alto commends CAISO and PG&E for refining the project scope in a manner that improves reliability while remaining focused on an efficient, targeted transmission solution.
    
2. Need for an Accelerated In-Service Date

While Palo Alto strongly supports the revised project scope, Palo Alto is concerned that the Draft Plan continues to reflect an in-service date of 2034, which does not align with the timing of observed and forecasted reliability violations.

As CAISO’s own reliability assessments demonstrate, thermal overloads on the Cooley Landing #1 and Ravenswood–Palo Alto #1 and #2 115 kV lines emerge as early as 2027 and worsen materially by 2030[3] due to increased load levels. Delaying the project’s completion until 2034 would leave Palo Alto and the surrounding system exposed to multiple years of identified reliability risk, despite the availability of a well-defined and now appropriately scoped transmission solution.

Palo Alto reiterates its prior position that:

• The need for the project is near-term, not distant;

• The revised scope further strengthens the case for earlier project delivery, given the enhanced capability of the line; and

• Advancing the project timeline would directly address CAISO-identified violations rather than prolong interim exposure.

Accordingly, Palo Alto urges CAISO to revise the Draft Plan to accelerate the project’s targeted in-service date, with the objective of having the New Ames Distribution–Palo Alto 115 kV project online no later than 2030, and earlier if feasible.

3. Palo Alto Supports Parallel-Track Execution
   
   Palo Alto recognizes that CAISO and PG&E have previously attributed the later in-service date to sequencing considerations associated with other PG&E work in the area. However, given the severity and timing of the reliability concerns, Palo Alto believes it is appropriate for CAISO and PG&E to re-examine opportunities to parallel-track activities, including:

• Preliminary engineering;
• Environmental review; and
• Construction planning and procurement.

Palo Alto is committed to work collaboratively with CAISO and PG&E to identify practical strategies to compress the overall project schedule, consistent with sound engineering and environmental practices. In Palo Alto’s view, initiating and advancing these efforts now is a prudent response to clearly identified reliability needs and rapid load growth already being observed in service.

4. Conclusion
   
   Palo Alto strongly supports the revised scope of the New Ames Distribution–Palo Alto 115 kV project, as included in the Draft 2025–2026 Transmission Plan and commends CAISO for incorporating higher-capacity conductors and targeted reconductoring. However, Palo Alto respectfully urges CAISO to align the project’s in-service date with the timing of documented reliability violations by accelerating the schedule well ahead of 2034.

Given the emergence of overloads beginning in 2027 and intensifying by 2030, advancing this project is essential to maintaining reliable service to Palo Alto customers and the broader Bay Area system.

[1] Draft 2025–2026 Transmission Plan, pp.83-84.

[2] Final Reliability Assessment Results for PG&E Greater Bay

[3] Id.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

No comments at this time.

3. Please provide your organization’s comments on the Economic Assessment.

No comments at this time.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

No comments at this time.

5. Please provide your organization’s comments on Frequency Response.

No comments at this time.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

No comments at this time.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

Clearway appreciates CAISO’s work and supports the proposed set of reliability-driven projects as a pragmatic response to the load growth and system conditions described in the Draft Plan. We also encourage CAISO to explicitly address short-circuit duty (SCD) mitigation sequencing and cost responsibility in the final plan. If SCD impacts of reliability-driven upgrades are not accounted for in the plan assumptions, mitigation can be pushed to generation Interconnection Customers even when the upgrades are not caused by those projects. Clearway recommends that CAISO clarify in the final plan whether the reliability analyses include the SCD mitigation needed for (a) previously approved upgrades and (b) upgrades recommended in this cycle, to ensure the mitigation is included alongside the approved or recommended upgrades.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

Clearway strongly supports approval of the Trout Canyon–Lugo 500 kV Line. This is a no-regrets project that addresses persistent constraints and enables deliverability for large volumes of renewables and storage needed to meet California’s goals.

However, Clearway is concerned that the benefits of Trout Canyon–Lugo will be materially limited without a credible path to address downstream constraints, especially the newly identified Mira Loma–Mesa limitation. The 2025 Transmission Plan Deliverability (TPD) Allocation Report states, “The 2025 TPD study identified a new Mira Loma-Mesa area constraint resulting from the removal of the Del Amo project.” This constraint has left ~16 GW of eligible TPD candidates without TPD in zones that have one of the highest quality resources because only 73 MW of TPD could be allocated. Clearway requests that the CAISO explore all options to address the Mira Loma–Mesa constraint, including any interim and operational mitigations.

Clearway requests that CAISO:

1. Quantify in the final Transmission Plan the TPD created by Trout Canyon–Lugo to enable better alignment between transmission planning and the reformed interconnection intake process;
2. Explain whether downstream constraints (including Mira Loma–Mesa) will prevent several high-quality resource zones from realizing meaningful TPD in upcoming allocation cycles, and identify the forum/timeline for evaluating mitigation options; and
3. Avoid over-reliance on assumptions that large volumes of new storage will materialize in dense load centers as a substitute for “wires” solutions, given development feasibility risks; instead, ensure the final plan transparently compares feasible alternatives and their timing.

Clearway also encourages CAISO to reassess whether the proposed in-service timing for Trout Canyon–Lugo can be advanced to better align with near-term procurement needs, including the 6 GW NQC procurement ordered in February by the CPUC. Interim or operational mitigations could also help address the near-term procurement need if it is not possible to accelerate construction of Trout Canyon-Lugo.

3. Please provide your organization’s comments on the Economic Assessment.

Clearway supports CAISO’s recommendation to approve the Gates – Los Banos #3 500 kV Line Series Compensation project and appreciates CAISO’s growing focus on the scale and persistence of congestion on major corridors.

Clearway also supports CAISO’s conclusion that the system needs additional 500 kV reinforcement on the San Joaquin Valley backbone (Path 15 / portions of Path 26). Considering the clear demonstration of the need for upgrades, we encourage CAISO to explore performing the technical work plan to identify preferred upgrade option extending from Tesla to Midway/Windhub on an expedited evaluation path that could result in an out-of-cycle TPP approval recommendation to the CAISO board.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

No comments.

5. Please provide your organization’s comments on Frequency Response.

No comments.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

Clearway is concerned by the widespread impact of the Mira Loma-Mesa constraint on available TPD as a result of the cancellation of the Del Amo project. Given the rapid buildout of new resources needed to meet the CPUC’s identified procurement needs, CAISO should take steps to avoid this type of unintended consequence in the future. Even a modification or delay of a major transmission upgrade could create downstream constraints with adverse impacts on available deliverability and interconnection feasibility. Clearway encourages CAISO to formalize a consistent approach where major project cancellations include: (i) a quantified assessment of the impact of the cancellation or modification on deliverability/interconnection due to downstream constraints, and (ii) a clearly defined plan and timeline to evaluate feasible mitigation options, including wires-based solutions where needed. 

In addition to our support for the San Joaquin Valley backbone upgrade, Clearway is also aware of significant obstacles for generators seeking to connect to the planned Manning substation. Clearway encourages CAISO to explore the potential value of an additional collector station in that area that could be networked to address the identified Path 15/Path 26 congestion.

Clearway appreciates CAISO’s leadership and stakeholder engagement in the 2025–2026 TPP.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

Environmental Defense Fund (EDF) appreciates the opportunity to provide comments on CAISO’s 2025-2026 Draft Transmission Plan. Transmission infrastructure investment is necessary and urgent to keep the grid affordable, reliable and help eliminate greenhouse gas emissions and local air pollution. California’s clean energy goals, growing electricity demand, and the integration of new resources all depend on a well-planned, thought-out transmission system and the investments identified in the plan. EDF generally approves of the 2025-2026 Draft TPP and the direction CAISO has set for the coming planning cycle.  

EDF supports the proposed reliability projects needed to serve load reliably across California. EDF acknowledges and appreciates CAISO’s attempt to reflect the increased rate of electricity demand growth reflected in California Energy Commission (CEC)’s 2024 Integrated Energy Policy Report (IEPR) in its planning.

In particular, EDF commends CAISO in utilizing advance conductors and grid enhancing technologies (GETs) to achieve reliability in the Mesa – Laguna Bell 230 kV #2 Upgrade, Lugo 500kV Reactive Power Reinforcement, and Ames Distribution – Palo Alto 115 kV line. This is the right outcome and is a no regrets investment for the ratepayer to make. However, EDF notes under the current process, GETs are still considered alternatives, which in practice limits their deployment and hinders potential cost savings. Although CAISO now formally considers non-wire alternatives as part of its standard alternatives analysis, often alternative solutions are hindered because of the plan’s embedded bias toward more conventional solutions. EDF urges CAISO to take note of the lessons learned from this part of the Transmission Planning Process (TPP) for the future. EDF is concerned that the planning process underutilizes non-wire solutions. GETs are currently evaluated after a project need has been identified and after a conventional solution has been assumed. By the time an additional line on an existing right-of-way has been sited, the planning process has already treated the new infrastructure as the default answer. GETs are evaluated against a conventional solution that was never required to justify its cost or necessity, which ends up placing the burden of proof on the cheaper option while the more expensive one goes unchallenged.

For existing right-of-way constraints, this framework should invert to a “GETs-first, justify the deviation” standard. The burden of proof should fall on incumbent utilities or intervenors to demonstrate why a conventional upgrade is more appropriate, not on proving that a GET is acceptable. For these reasons, EDF urges CAISO to consider this approach to deploy grid solutions quickly and affordably.

EDF appreciates CAISO’s decision to utilize the Mesa – Laguna Bell 230 kV #2 Upgrade as a near-term bridge to meet the anticipated 10-year planning horizon for the LA Basin Area. EDF highlights the previously approved Serrano-Del Amo-Mesa 500kV Transmission Reinforcement project that ultimately was canceled due to significant cost increases. EDF acknowledges transmission costs have increased drastically over the past few years; however, the referenced project went from a cost estimate of $1.125B in the 2022-2023 cycle to $5.0B in the 2025-2026 draft plan. For projects that end up going drastically overbudget, EDF requests that CAISO publish detailed findings on those costs and underlying assumptions to ensure that there are no implications for future projects. This transparency is essential not only for ratepayer accountability but also to protect the credibility of the transmission planning process as a whole. Notwithstanding these cost concerns, EDF reaffirms that transmission investment is necessary, and cost overruns should prompt better oversight, not reduced ambition.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

EDF notes that the overarching policy objective for CAISO is to meet renewable energy and greenhouse gas (GHG) reduction targets while maintaining reliability. To best do so, CAISO should continue to set itself up in advance for the development of long lead-time (LLT) resources. LLT resources such as offshore wind and geothermal require transmission infrastructure that must be planned years in advance of completion. Acting proactively now ensures that the LLT resources California needs to meet its clean energy goals are ready to meet the moment of growing demand.  

EDF supports the policy-driven projects recommended for approval. Projects like the proposed Trout-Canyon-Lugo 500kV line represent forward-looking infrastructure that supports both California’s reliability goals and future clean energy targets. EDF notes that the east-west connection will help relieve congestion on the Lugo-Victorville bottleneck and support the delivery of out-of-state wind resources.

Furthermore, the infrastructure needed for emerging resources like offshore wind and geothermal takes significant time, and CAISO should invest in planning for the interconnection of these resources and ensure they can be delivered where load is located. To do so, CAISO should treat LLT transmission planning as a standing priority across TPP cycles, not an ad hoc exercise. EDF believes that this standing priority will help yield additional certainty and reduce development costs as a result.

EDF notes that offshore wind development in California will not only serve California ratepayers, but the state is the only one on the west coast with an authorized lease from the Federal government. California serves as the regional gateway for accessing offshore wind across the West. As a result, California is uniquely positioned to lead early deployment and shape the broader market. In the near to medium term, other Western states interested in procuring offshore wind energy will likely depend on projects developed off California’s coast.

Given this dynamic, EDF encourages CAISO to proactively plan for how LLT resources, like offshore wind, can be integrated into and exported across the Western grid.

3. Please provide your organization’s comments on the Economic Assessment.

EDF supports CAISO’s Economic Assessment and the proposed Gates – Los Banos #3 500kV Line Series Compensation. The proposed project is a “no brainer” near-term measure that will help reduce congestion while a long-term solution is finalized.

EDF acknowledges that Path 15 faces significant congestion issues. Recent forecasts predict $1.8B in aggregate congestion costs by 2035, which are significantly higher than what was last studied. Given that 2035 is the earliest year studied in this TPP cycle, it is reasonable to assume significant congestion costs arise even sooner. Because of this, EDF encourages CAISO to act sooner rather than later to accelerate the full backbone reinforcement study and revised congestion revenue methodology so that Alternative 6 can be approved in the next cycle. Acting now will result in cost savings for the State.

While much of the discussion surrounding Path 15 has rightfully focused on the economic case, EDF notes that addressing Path 15 congestion is also critical to advancing policy goals. EDF observes that there is a substantial and growing pipeline of utility-scale renewable projects that will become feasible if Path 15 congestion is relieved. The urgency of accelerating the full backbone reinforcement study will move California’s energy goals forward and ultimately save costs.

EDF also notes that the launch of the Extended Day-Ahead Market (EDAM) on May 1, 2026, may reduce some congestion along Path 15 by alleviating curtailment problems in Fresno and Kern by utilizing export paths eastward. EDF acknowledges that although this congestion issue would only be slightly alleviated, and that an additional 500 kV line is still necessary.

Nonetheless, EDF urges CAISO to treat EDAM’s launch as an opportunity and data-gathering exercise. Power flows generated by expanded western market participation will reveal congestion patterns that may confirm or modify specific transmission investments. EDF strongly encourages CAISO to analyze power flow data and feed the findings into the next TPP cycle to refine investments.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

EDF has no comments at this time.

5. Please provide your organization’s comments on Frequency Response.

EDF has no comments at this time.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

EDF encourages CAISO to meaningfully incorporate Tribal engagement into the 2025-2026 TPP and future planning cycles. FERC Order 1920 requires transmission providers to account for federally recognized Tribal laws and policy goals when developing long-term planning scenarios. EDF recommends that CAISO treat this mandate as a floor, not a ceiling.

A report from EDF and Clean Air Task Force (CATF) demonstrates the benefits of Tribal engagement.[1] By making the Morongo Band of Mission Indians a participating transmission owner rather than compensating the Tribe for a simple right-of-way, Southern California Edison (SCE) accelerated project delivery up to seven years and finished five months ahead of schedule and under budget. When communities have a stake in a project’s success, local opposition diminishes and the permitting and siting processes that most commonly trigger delays are streamlined.

EDF urges CAISO to incorporate Tribal policy goals as substantive inputs into its long-term scenario developing, encourage Tribal co-ownership structures for LLT projects near Tribal lands, and work with the CPUC and utilities to build a standing Tribal engagement framework rooted in long-term relationship building.

EDF thanks CAISO for the opportunity to comment on the 2025-26 Transmission Planning Process Draft Plan.

[1] “Beyond the Wires: Community Benefits from Transmission Projects | EDF,” November 10, 2025, https://www.edf.org/beyond-wires-community-benefits-transmission-projects.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

EDFps appreciates the extensive technical studies and comprehensive transmission solutions proposed by the ISO in the 2025-2026 Draft Transmission Plan. We support the approval of the 33 recommended reliability-driven projects, which represent a reasonable response to the significant load growth and evolving system conditions documented in this cycle. EDFps supports the inclusion of durable, physical transmission solutions, as expanded physical capacity provides superior long-term grid stability compared to a continued reliance on temporary operational schemes.

Furthermore, we support the strategic deployment of advanced conductors and other grid-enhancing technologies (GETs) where they are technically and economically appropriate to enhance system efficiency.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

EDFps appreciates the extensive work performed by the ISO and the CPUC IRP team to evaluate the policy-driven transmission projects required to meet California’s ambitious clean energy goals. We support the overall set of policy-driven projects recommended in the Draft 2025-2026 Transmission Plan in response to the state’s evolving resource portfolios. While we favor the ISO’s transition toward more durable, physical grid reinforcements, we urge the ISO to remain mindful of how project cancellations and new downstream constraints impact the commercial viability of resources already in the interconnection queue.

We strongly support the approval of the Trout Canyon-Lugo 500 kV project. This critical no-regrets investment provides a networked solution that addresses some of the system's most persistent constraints, including the Lugo-Victorville and East of Pisgah (GLW-VEA) area constraints. By unlocking approximately 7 GW of resource deliverability, this project is essential for integrating the vast volumes of resources identified in the CPUC base portfolios. Furthermore, EDFps supports this project as a superior alternative to continued reliance on over-subscribed operational schemes like the Sloan Canyon and Lugo-Victorville Remedial Action Schemes (RAS).

While EDFps understands the ISO’s rationale for cancelling the Serrano-Del Amo-Mesa 500 kV project due to significant cost increases, we are greatly concerned by the resulting downstream impacts. The removal of this major reinforcement from planning models has led to the identification of a new, binding Mira Loma-Mesa area constraint. This bottleneck effectively traps the deliverability of resources into the LA Basin, negating some of the benefits provided by the Trout Canyon-Lugo on-ramp and resulting in a substantial loss of available deliverability.

The 2025 Transmission Plan Deliverability (TPD) Allocation Report confirms the crushing impact of this unaddressed constraint, showing that zero MW of deliverability were allocated to seeking generators in the North of Lugo (NOL) and SDG&E areas during the 2025 cycle. This lack of deliverability threatens the viability of numerous projects, particularly those in Cluster 14 and prior, which may now face multi-year delays. 

3. Please provide your organization’s comments on the Economic Assessment.

EDFps appreciates the ISO’s robust economic assessment and the clear recognition of the urgent need to address escalating congestion on Path 15. We support the proposed phased approval process, beginning with the Gates-Los Banos #3 500 kV Line Series Compensation, which provides immediate relief without delaying more significant long-term solutions like the Windhub-Tesla 500 kV line. Expediting the necessary analysis for this larger reinforcement is critical to ensuring it is ready for approval in the 2026-27 TPP, as it will be instrumental in increasing deliverability for high-priority clean energy zones in Fresno and Kern counties. 

Furthermore, EDFps strongly echoes the concerns raised by ACP-CA regarding the conservative nature of the current Transmission Economic Assessment Methodology (TEAM). We believe it is appropriate to evaluate how the current framework may under-report project benefits, and we are pleased to see the ISO utilizing more realistic congestion revenue treatments in its preliminary evaluations. We fully support the ISO's commitment to officially updating the TEAM framework in 2026 to ensure economic assessments accurately reflect the evolving grid’s needs and the true value of congestion mitigation. 

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

No comments at this time.

5. Please provide your organization’s comments on Frequency Response.

EDFps supports the ISO’s continued focus on frequency response as inverter-based resources (IBRs) increasingly displace conventional synchronous generation across the CAISO system. We support the ongoing assessment of frequency response obligations and FERC Order 842 requirements to ensure that all new IBRs contribute effectively to grid stability and system recovery.

Furthermore, as the share of IBRs grows, we encourage the ISO to evaluate whether existing market products and operational incentives provide adequate compensation for the headroom-based frequency response these resources provide, ensuring these vital capabilities are fully leveraged to support the reliable integration of clean energy. 

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

No comments at this time. 

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

No comments.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

Redwood Coast Energy Authority (RCEA) and Sonoma Clean Power (SCP) file these comments jointly. As transmission constrained Northern California LSEs, RCEA and SCP have similar recommendations for the 2025-2026 TPP. RCEA and SCP are henceforth referred to as the Joint CCAs.

Policy-Driven Transmission and TPD Scarcity

After accounting for the cancellation of the Del Amo–Mesa–Serrano 500 kV project, the Joint CCAs note that the Draft Plan reflects only a modest net increase in policy-driven transmission investment. Given the severe scarcity of TPD today, the Joint CCAs view this outcome as unacceptable.

While the queue has been cleared as a response to recent Interconnection Process Enhancements, there is still very little TPD availability. Without new policy-driven deliverability, the pipeline of viable projects in Cluster 16 and future clusters will be extremely limited, particularly for diverse resources that cannot site opportunistically in unconstrained areas. The Joint CCAs urge CAISO to treat policy-driven expansion of TPD as a core objective of the TPP rather than a secondary outcome.

Support for Northern California Development and VCIP

The Joint CCAs appreciate CAISO’s recognition of Valley Clean Infrastructure Project (VCIP) in its discussion of Path 15 constraints. The Joint CCAs urge CAISO to more actively support more opportunities to mitigate Path 15 and Path 26 congestion by alleviating TPD constraints for cost-effective generation development in Northern California. Past SCP comments have highlighted that prior RESOLVE modeling does not fully capture the value of Northern California generation in reducing transfer path congestion.

The Joint CCAs recommend that CAISO explicitly credit policy-driven TPD expansion in Northern California with avoided economic upgrades before advancing larger-scale backbone reinforcements in future cycles.  Additionally, the Joint CCAs ask CAISO to review the design of the New Humboldt to Collinsville 500 kV line and New Humboldt to Fern Road 500kV line to assess whether they can be leveraged to improve TPD availability for a diverse range of resources in Northern California alongside providing access to offshore wind, including the ~3 GW of incremental geothermal and the onshore wind resources mapped in the final IRP portfolios that will be studied in the 2026-27 TPP. Modifications to these projects could include additional staging or reconfiguring to allow for a phased build out with additional incremental TPD for local projects.

Northeast California Expansion

The CPUC requested the CAISO study 1,150 MW of capacity in Northeastern California outside the ISO system.  This wind resource is especially valuable to the system, given its ability to deliver direct to the PG&E system and resource diversity benefits.  Northeastern California is further highlighted as an important resource area in the forthcoming 2026-2027 TPP, where the CPUC also maps in-state geothermal and access to Northern Nevada resources.  The Joint CCAs request the CAISO to not simply map these resources at Malin, but consider potential solutions to expand their system with a direct intertie at the Hilltop substation in NVE territory.  Relying on delivery at Malin adds significant wheeling costs and requires resources important to California’s climate and reliability targets to compete with the infrastructure demands of other states.  The Joint CCAs would like the CAISO expansion to Hilltop to be evaluated in the 2025-26 TPP, at least at a high-level, to enable an actionable project in the 2026-27 TPP. 

Charging Deliverability and Early Study of Energy-Only Resources

The Joint CCAs encourage CAISO to consider performing a charging deliverability study for the modeled policy portfolio in the 2025–2026 TPP, rather than deferring this analysis until the subsequent planning cycle. Evaluating charging deliverability now would provide valuable insight into the extent to which energy-only and storage-heavy resources can reliably contribute across specific slices of the day, consistent with issues currently under consideration in the CPUC’s Resource Adequacy proceeding. Earlier assessment of charging constraints and opportunities would help accelerate benefits associated with energy-only resources’ reliability contributions, inform procurement and siting decisions, and reduce the risk that transmission limitations unnecessarily constrain otherwise viable, policy-aligned resources. The Joint CCAs believe advancing this analysis in parallel with the current TPP would better align transmission planning with evolving RA frameworks and support more efficient implementation of state policy objectives.

3. Please provide your organization’s comments on the Economic Assessment.

Redwood Coast Energy Authority (RCEA) and Sonoma Clean Power (SCP) file these comments jointly. As transmission constrained Northern California LSEs, RCEA and SCP have similar recommendations for the 2025-2026 TPP. RCEA and SCP are henceforth referred to as the Joint CCAs.

Path 15 Congestion and Backbone Reinforcement

The Joint CCAs support approval of the Gates–Los Banos #3 500 kV Line Series Compensation project as a prudent near-term mitigation measure. However, the Joint CCAs remain concerned that the Draft Plan acknowledges the need for additional 500 kV reinforcement extending from Windhub to Tesla while deferring this solution to the 2026–2027 planning cycle. CAISO’s own production cost modeling shows Path 15 as the most economically congested corridor in California, with congestion costs exceeding $1.7 billion annually by the mid-2030s. Incremental and operational mitigations alone are insufficient to address this trend. The Joint CCAs urge CAISO to advance engineering, functional specification development, and competitive readiness for the identified backbone reinforcement in parallel with this Plan to avoid prolonged congestion costs and inefficient use of the existing grid.  The CAISO should also consider alternatives that provide the faster path to energization by leveraging existing infrastructure and expedited permitting processes.  Additionally, as described above, The Joint CCA asks CAISO to investigate whether additional policy-driven TPD and import capacity in Northern California can reduce the scope needed for Path 15 upgrades.

Path 26 Constraints and Long-Term Solutions

The Joint CCA recognize the value of low- and no-capital operational mitigations identified for the Path 26 corridor and agrees these measures can provide useful short-term relief. However, the Joint CCAs caution against treating these actions as a substitute for durable infrastructure. The Draft Plan confirms recurring Path 26 congestion under both north-to-south and south-to-north flows, with material economic impacts. The Joint CCAs encourage CAISO to identify longer-term physical reinforcement options within this Plan and to coordinate with the CPUC to ensure Path 26 constraints are fully represented in Integrated Resource Planning (IRP) modeling and procurement outcomes.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

No Comments

5. Please provide your organization’s comments on Frequency Response.

No Comments

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

No Comments

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

Fervo Energy Company (“Fervo”) supports the California Independent System Operator’s (“CAISO”) proposed reliability-driven project set. Fervo greatly appreciates CAISO’s efforts to conduct studies and propose transmission solutions in the 2025-26 Draft Transmission Plan (“TPP”). Fervo thanks the CAISO for the work to advance the notable set of proposed projects to advance reliability across the system.  

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

A.  Trout Canyon-Lugo 500 kV Line: Support for Approval, with Concern About In-Service Date 

Fervo supports approval of the Trout Canyon-Lugo 500 kV transmission line, which is critical infrastructure for delivering geothermal and other clean firm resources to California load centers. This project unlocks approximately 7 GW of deliverability in the Lugo-Victorville area and is essential to enabling the diverse, reliable clean energy portfolio embedded in California Public Utilities Commission’s (“CPUC”) 2025-26 TPP portfolios – including roughly 500 MW of geothermal resources in that corridor. Fervo urges CAISO to move expeditiously to approve and advance the project through competitive solicitation. 

Fervo is concerned that the projected 2035 in-service date is incompatible with California's 2032 resource adequacy and clean energy targets. Geothermal development timelines require transmission certainty well in advance, and a 2035 in-service date forecloses the ability of geothermal resources already in CPUC's portfolios to contribute to the grid by 2032. CAISO should identify whether any process changes – such as early transmission owner engagement or parallel permitting – could accelerate the in-service date and transparently report on this analysis in the final Transmission Plan. 

B.  Deliverability Reservations for Geothermal: Request for More Detail and Alignment with CPUC Portfolios 

The Draft Transmission Plan, as written, does not clearly explain the methodology for deliverability reservations. Fervo thanks the CAISO for their close coordination on this topic to date and commits to working with the CAISO and the CPUC to provide the most updated information regarding Enhanced Geothermal Systems (“EGS”) to improve the assumptions that drive these reservations.  

We ask that the CAISO coordinate closely with the CPUC to ensure that the deliverability reservations remain consistent with the CPUC’s 2025-2026 Base Case, which includes 366 MW of in-development Utah geothermal and an additional 23 MW of “generic mapped” Utah geothermal, totaling 389 MW. Fervo would like to work with the CAISO to understand the current 90 MW deliverability reservation. Deliverability reservations are critical to ensure long-lead-time (“LLT”) resources like geothermal can deliver firm power to the CAISO system, and Fervo commits to supporting the CAISO in planning for EGS resource delivery.  

C.  Interregional Transmission for Utah Geothermal: Commitment Required in the 2027-2028 TPP Cycle 

The 2025-26 Draft TPP Portfolio Decision explicitly commits to planning interregional transmission for out-of-state (“OOS”) wind resources in the next planning cycle (p. 59). Fervo urges the CAISO to apply the same commitment to OOS geothermal resources and to state in the final 2025-26 Transmission Plan that interregional transmission planning for Utah geothermal will be undertaken in the 2027-2028 TPP. 

The 2027-28 TPP is the last planning cycle capable of producing transmission that could support the Utah geothermal resources included in the CPUC portfolio for deliveries by 2032. Utah geothermal resources are already embedded in CPUC's portfolios at scale (389 MW in the 2025-26 base case) and are uniquely valuable as dispatchable, locational, non-intermittent clean firm resources. The CPUC's portfolio decision itself recognizes geothermal as meeting the criteria for LLT treatment – resources with "longer and more difficult development processes," limited by geographic location, but with "unique value" for reliability (p. 58). If CAISO does not commit to evaluating interregional transmission solutions in 2027-28, there will be no viable pathway for Utah geothermal to contribute to California's grid before 2032. 

Treating geothermal on a par with OOS wind is procedurally consistent with the existing framework for OOS wind and essential to preserving California's ability to meet its reliability and clean energy obligations with a diverse resource mix. Fervo requests that CAISO include an explicit commitment to this effect in the final 2025-26 Transmission Plan. 

3. Please provide your organization’s comments on the Economic Assessment.

Fervo has no specific comments on the economic assessment at this time. Fervo notes, however, that congestion relief on Path 15 and related corridors directly affects the deliverability of geothermal and other clean firm resources in central California. Fervo supports CAISO's phased approach to the Path 15 corridor and encourages CAISO to complete the analyses necessary to advance a larger solution for approval in the 2026-27 cycle.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

The current Maximum Import Capability (“MIC”) Expansion Request process does not provide the commercial certainty required by load-serving entities relying on out-of-state geothermal and other OOS resources embedded in the CPUC's portfolios. Fervo supports a MIC Enhancements initiative and urges CAISO to take it up in the 2026-27 planning cycle. Addressing MIC limitations is a prerequisite for ensuring Utah geothermal can reliably deliver to California at the scale envisioned by CPUC's resource plan. 

5. Please provide your organization’s comments on Frequency Response.

Fervo has no specific comments on the frequency response assessment at this time. 

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

Fervo is a leading developer of utility-scale EGS projects, leveraging advanced drilling and subsurface technologies to access new geothermal heat resources previously deemed unsuitable due to limitations in conventional geothermal drilling methods. EGS already provides reliable, clean, and dispatchable power today and is rapidly scaling to meet the energy demands of the future.

Fervo has a large portfolio of lease holdings across the West, including in California, and is actively developing projects to support the California grid, including the 500-megawatt Cape Station project in Beaver County, Utah. Cape Station’s full capacity is contracted with California Load Serving Entities (“LSEs”) to meet procurement orders under D.21-06-035.

Fervo appreciates CAISO's continued efforts to align transmission planning with California's resource adequacy and clean energy goals. In summary, Fervo's comments raise three interconnected issues that CAISO should address in the final 2025-26 Transmission Plan: 

1.  Trout Canyon-Lugo In-Service Date. Fervo supports approval of the Trout Canyon-Lugo 500 kV line but urges CAISO to examine whether the projected 2035 in-service date can be accelerated. A 2035 date is incompatible with California's 2032 reliability targets and forecloses near-term deliverability for geothermal resources already embedded in CPUC's portfolios. 

2.  Deliverability Reservation Coordination. Fervo thanks the CAISO for its coordination on deliverability reservations and requests further transparency to understand CAISO’s methodology for this process. Fervo respectfully asks that CAISO coordinate with the CPUC to ensure that the 2025-2026 base case Utah geothermal MWs are incorporated into the TPP to align with procedural guidance.  

3.  Interregional Transmission for Utah Geothermal. Just as CAISO has committed to studying interregional transmission for OOS wind in the next planning cycle, it should make the same commitment for OOS geothermal. The 2027-28 TPP is the last cycle capable of producing transmission in-service by 2032. Without a firm commitment to study interregional solutions for Utah geothermal in that cycle, there is no viable pathway for these resources to serve California by the target date. 

Fervo looks forward to continued engagement with CAISO and stakeholders to advance the transmission planning and interconnection solutions necessary to bring Utah geothermal resources online in time to serve California by 2032. 

Respectfully submitted, 

Sarah Harper ("Harper")

Fervo Energy Government Affairs - CA, NM 

sarah.harper@fervoenergy.com

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

No comment.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

Golden State Clean Energy (“GSCE”) generally supports the draft 2025-2026 Transmission Plan and continues to believe that additional transmission infrastructure will be necessary to improve deliverability and access to in-state renewable resources. Few policy-driven projects are recommended for approval this cycle, none of which seem to represent major upgrades targeting important in-state renewable resource areas. To that end, the solution to Path 15 corridor congestion should also help facilitate interconnecting solar and battery storage resources in the San Joaquin Valley.

The policy-driven analysis for the Fresno study area highlights the importance of the economic analysis when looking to integrate new solar resources in support of California’s decarbonization goals. The Fresno area includes 19.4 GW of resources in the base case by 2040, including 13.5 GW of solar.[1]  There is currently little available deliverability in the Fresno area to interconnect planned resource additions, but the draft plan does not recommend approving new policy-driven upgrades in the area. Solar has a low HSN on-peak capacity contribution in the policy-driven analysis, which results in few policy-driven projects that are intended to benefit predominately solar rich areas, even though integrating new solar is critical to state policy. This puts more emphasis on the economic analysis to drive new transmission that supports solar based on excessive curtailment identified in the off-peak deliverability studies. In the Fresno area, a large number of constraints are identified in the off-peak analysis, indicating excessive curtailment and showing that additional infrastructure investments are needed to facilitate new solar in this area. A total of 30 off-peak deliverability constraints were identified in the Fresno area in the draft plan, and 17 of those 30 constraints identified the potential mitigation as needed “if economic”.[2] GSCE urges CAISO to address the need for transmission investments in the Fresno area that enable additional solar development when designing the solution to Path 15 corridor congestion. The many lower voltage constraints identified in the off-peak deliverability analysis in the Fresno area suggest a higher voltage solution is needed and likely more cost-effective for supporting the 19.4 GW of resources in the base case.

[1] CAISO, draft 2025-2026 Transmission Plan, Appendix F, at pg. 87 (Table F.8-1), April 7, 2026.

[2] CAISO, draft 2025-2026 Transmission Plan, Appendix F, at pg. 95-96 (Table F.8-15), April 7, 2026.

3. Please provide your organization’s comments on the Economic Assessment.

GSCE appreciates CAISO’s economic analysis and the focus on the Path 15 and Path 26 corridors that are critical to transferring electricity across the state. GSCE supports CAISO’s decision to take a comprehensive look at the region and backbone grid and identify a solution in the next TPP cycle.  The solution, or set of solutions, must meaningfully address the significant congestion on Path 15.  GSCE supports finding a holistic solution that addresses the congestion issues and taking the time to study the configuration that will work best to resolve congestion and provide benefits of renewable generation integration in Northern California. GSCE also supports the approval of the Gates–Los Banos #3 500 kV Line Series Compensation in this cycle as a least-regrets upgrade for the region that can move forward now while complementing any additional project approved in the region in the next TPP cycle.

CAISO should look to solutions that can expedite construction and cost savings associated with faster congestion relief. The draft plan identifies $1.8 billion in annual congestion costs by 2035,^[1] the earliest study year in this TPP cycle, with increasing congestion costs by 2040.^[2] This is consistent with the CAISO’s Department of Market Monitoring reports, which already identify similar congestion trends in the market.^[3] Given these data points, it is reasonable to assume significant congestion costs arise before 2035.  The significant and increasing congestion costs support the need to bring new Path 15 corridor infrastructure in-service as soon as possible. CAISO should leverage the Valley Clean Infrastructure Plan (“VCIP”) currently under development by the Westlands Water District (“WWD”) and GSCE. VCIP provides a unique opportunity to expedite Path 15 infrastructure development, with its already certified Program Environmental Impact Report and WWD’s existing statutory authority to construct transmission.  GSCE supports CAISO completing engineering studies to identify a comprehensive regional solution and then prioritizing solutions, like VCIP, that can be constructed quickly.

The draft plan correctly specifies the need for a separate right of way for the proposed new 500 kV line in the San Joaquin Valley. The region’s existing 500 kV facilities and corridor are significantly impacted. Further, to access renewable resource zones, the new 500 kV infrastructure should be routed close to planned or permitted renewable resources in the San Joaquin Valley. Addressing Path 15 corridor congestion provides an opportunity to do a multi-benefit transmission project in cost-effective manner by also integrating new resources in the San Joaquin Valley, particularly the Fresno resource area as explained in our response to Question 2. If new infrastructure to address congestion is instead located within the existing Path 15 corridor, new resources will be required to develop lengthy and costly gen-ties that may have to navigate crossing the I-5 freeway or productive agricultural land that is not planning to fallow, thus increasing the uncertainty and cost of solar development in this area. A Path 15 corridor solution that also integrates renewables can further California land use and environmental planning that has identified solar in the San Joaquin Valley as a low conflict land use.

GSCE believes VCIP is a cost-effective solution to help address the identified Path 15 corridor congestion and that VCIP can be developed on an expedited timeline given AB 2661 and the certified Program Environmental Impact Report. The location of VCIP also provides a solution using a new right-of-way corridor. VCIP is consistent with the needs CAISO has identified in this transmission plan.

[1] CAISO, draft 2025-2026 Transmission Plan, at pg. 119 (Table 4-1), April 7, 2026.

[2] CAISO, draft 2025-2026 Transmission Plan, at pg. 119 (Table 4-1), April 7, 2026.

[3] CAISO Dept. of Market Monitoring, 2025 Q4 Report on Market Issues and Performance, at pg. 84-86, March 2026 (see especially Figure 6.12).

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

No comment.

5. Please provide your organization’s comments on Frequency Response.

No comment.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

Golden State Clean Energy supports the draft 2025-2026 Transmission Plan and urges the CAISO Board to approve the draft plan.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

Regarding the recommended reliability-driven upgrades, particularly the Tesla – Trimble – Metcalf corridor and broader South Bay Area projects, the ISO must actively prioritize the use of advanced, high-capacity conductors. Upgrading existing rights-of-way with advanced conductors serves as a critical, "no-regrets" planning strategy to hedge against forecast uncertainty. While the South Bay is facing unprecedented load growth projections—driven in part by the proliferation of highly localized "edge" computing and AI infrastructure—traditional load forecasting models remain in transition, and hyperscale interconnection requests are volatile. Right-sizing these reliability upgrades by utilizing advanced conductors ensures the grid can safely accommodate potential exponential load growth while avoiding the stranded costs associated with building massive new infrastructure for loads that may ultimately fail to materialize or relocate out of state.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

We strongly support the development of the proposed 180-mile Trout Canyon to Lugo 500 kV transmission line. As California rapidly transitions its resource mix to meet SB 100 mandates, maximizing regional energy integration is essential. We recommend that the ISO ensure the development of the Trout Canyon – Lugo project is closely coordinated with other out-of-state transmission initiatives. Doing so will optimize the import of high-value, diverse renewable resources—specifically wind, solar, and geothermal generation from Nevada and the broader interior West—providing critical reliability and resource adequacy benefits to the CAISO balancing authority.

3. Please provide your organization’s comments on the Economic Assessment.

We appreciate the economic assessment, particularly the ten-alternative Path 26 study (§G.9.2), the nineteen-alternative Path 15 corridor study (§G.9.3), and the dedicated Las Aguilas – Moss Landing evaluation (§G.9.4). The transparency around the TEAM methodology revisions to congestion revenue allocation (§G.2.4) is especially valuable.

With the goal of right-sizing the grid for highly localized, unforecasted load growth in mind, we would like to raise one observation for the CAISO's consideration regarding the scope of the economic assessment. A cross-reference between trailing-12-month OASIS shadow price data and the Appendix G constraint list suggests that several lower-voltage transmission elements experiencing sustained operational congestion fall outside the PCM's current constraint scope and therefore receive no individualized economic assessment. 

We submit this not as a critique of the methodology, the ISO's modeling choices are well-reasoned and documented, but as an empirical data point that may be useful for scoping future cycles to capture the impact of distributed load growth.

Using publicly available CAISO OASIS LMP data, GridLab built an independent shadow-price analysis covering 441 constrained transmission elements over the trailing 12 months. For each element, we calculated a shadow-price-hours metric (aggregated positive shadow price × hours binding) and an estimated congestion cost proxy.

The top ten elements by this estimated cost proxy are:

(Note: Full details can be accessed at: https://nidzae.github.io/caiso-congestion-analysis/. The "Est. Cost Proxy" is a screening metric intended to rank constraints by operational impact, not a direct replacement for PCM congestion cost figures.)

We would  respectfully note that the following sub-transmission lines from the data above are not currently reflected in the top-ranked congestion tables (§G.7-1, §G.7-5, or §G.7-9) for this cycle:

• Control – Tap188 115 kV

• Control – Tap189 115 kV

• SC21A Tap – Arvin 70 kV

• Los Banos 70/230 kV Transformer

• El Cajon – Los Coches 69 kV

• Le Grand – Adra Tap 115 kV

We request that the CAISO consider whether historical OASIS shadow-price-hours data could be incorporated as a complementary screening input to identify persistently-binding lower-voltage constraints (below 230 kV) that may warrant inclusion in the economic assessment. Furthermore, we request the CAISO consider whether specific lower-voltage elements identified above, particularly those with over 2,000 binding hours per year, could receive individualized economic review within the current cycle if time permits.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

(No comment)

5. Please provide your organization’s comments on Frequency Response.

(No comment)

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

The overarching theme of these comments is the urgent need to right-size our grid investments for future load growth. As the state grapples with an unprecedented influx of data center interconnection requests, we should strategically differentiate between macro and micro data center loads.

While the ISO is prudently evaluating transmission upgrades to serve large-scale data centers, recent market indicators suggest a significant portion of those queue requests may ultimately prove speculative. Conversely, the load from "micro" or "edge" data centers—low-latency facilities required to support autonomous vehicle fleets, smart city infrastructure, and localized AI inference—is actively embedding itself into our dense urban and sub-transmission networks today.

To prevent stranding capital for hyperscale load that may never materialize, the CAISO should heavily prioritize rapid-deployment solutions like advanced reconductoring and Grid Enhancing Technologies (GETs) to address the immediate, highly localized edge computing loads materializing on our lower-voltage corridors.

Furthermore, achieving true least-cost grid solutions requires comprehensively planning these transmission upgrades in tandem with the location and storage duration of battery projects. A prime example of this necessary synergy in the current plan is the Mesa–Laguna Bell 230 kV #2 upgrade. By utilizing advanced conductors for this corridor, the ISO can successfully overcome the charging limitations for battery storage situated in the highly constrained South of Mesa load pocket within the Western LA Basin. Moving forward, realizing the full ratepayer value of this infrastructure co-planning will require close and continuous coordination with the CPUC to ensure that the procurement of the additional megawatt-hours of storage unlocked by this upgrade is thoroughly competitive.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

GLW appreciates CAISO’s continued leadership in advancing the 2025–2026 Transmission Planning Process (“TPP”) and commends CAISO for recommending the Trout Canyon–Lugo 500 kV project for approval this cycle. This is a critical step toward addressing one of the most binding constraints on the system and enabling the next phase of transmission expansion needed to support California’s clean energy and reliability goals.

The Trout Canyon–Lugo project represents a no-regrets solution under a wide range of resource portfolio outcomes. It directly addresses the most persistent and material constraints identified in both the 2035 and 2040 planning horizons, including the Lugo–Victorville interface and related East of Pisgah deliverability limitations. These constraints have continued to intensify over successive TPP cycles, and it is now clear that incremental solutions and continued reliance on remedial action schemes are no longer sufficient to manage system conditions at the scale required.

Trout Canyon–Lugo provides a comprehensive, networked solution that resolves multiple constraints simultaneously, improves deliverability of resources, and contributes to enabling the large volumes of renewable generation and storage needed to be developed for California to meet its Renewable Portfolio Standard (“RPS”) and long-term decarbonization targets.

GLW believes the selected solution represents the most cost-effective and efficient path forward to deliver needed capacity, improve reliability, and reduce long-term system costs.

GLW appreciates CAISO’s thoughtful evaluation and decisive action, and supports continued focus on large-scale, durable transmission solutions that can meet California’s growing demand and evolving resource mix.

3. Please provide your organization’s comments on the Economic Assessment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

The City and County of San Francisco (the “City”) appreciates the opportunity to comment on the CAISO’s 2025-2026 Draft Transmission Plan (“Draft Plan”) posted on April 7, 2026, and the material presented at the CAISO Stakeholder meeting on April 15, 2026. The City’s comments are primarily focused on CAISO’s evaluation of the Warnerville–Newark Transmission Expansion Project (WaNTEP).

1. CAISO Recognition of the Potential Benefits of Upgrading the Warnerville–Newark Path
   
   The City appreciates CAISO’s acknowledgment in the Draft Plan that upgrading the existing Warnerville–Newark transmission path may provide meaningful system benefits. The Draft Plan states that the CAISO recognizes the potential benefits of upgrading the Warnerville–Newark path to a higher capacity and notes that such upgrades could strengthen the 230 kV network at Newark and potentially enable additional renewable resource integration in the Newark–Warnerville area. The Draft Plan further recognizes that, while such capabilities are not required in the current planning cycle, steadily increasing load growth in the Greater Bay Area suggests that additional capacity may be required in future planning cycles.[1]

CAISO’s acknowledgment of the potential benefits of upgrading the Warnerville–Newark path is consistent with the City’s prior comments submitted during the Preliminary Reliability Assessment.[2]  As demonstrated in those comments, multiple WaNTEP configurations eliminate or materially reduce P1, P6, and P7 contingency overloads on critical 230 kV facilities serving the Greater Bay Area in both the 2035 and 2040 study horizons, confirming that this corridor functions as a structural reinforcement that preserves long-term transfer capability.

2. WaNTEP and the Tesla–Trimble–Metcalf Project Were Not Evaluated on an Equivalent Basis

The City is concerned that evaluating only a narrow subset of potential WaNTEP configurations biases the comparison toward projects optimized to address near-term overload relief, rather than alternatives that provide corridor-level reinforcement and long-term system optionality. As a result, the Draft Plan does not reflect a like-for-like assessment of solutions intended to meet different planning objectives.

While the City recognizes CAISO’s obligation to identify near-term reliability solutions, the City respectfully disagrees with the conclusion that WaNTEP is not a viable alternative when compared to the Tesla–Trimble–Metcalf 230 kV Corridor Expansion. Appendix B of the Draft Plan describes how WaNTEP was considered as an alternative; however, CAISO evaluated only a limited subset of WaNTEP configurations and did not assess the full range of configurations previously provided by the City. In particular, the analysis appears to have focused on a single 1,000 MW HVDC injection from Tesla to Newark and a single 230 kV AC configuration, rather than the broader set of WaNTEP configurations developed to address longer-term system needs and optionality.[3] In addition, CAISO did not consider the potential to address the near-term overload issues downstream of the Newark substation in conjunction with WaNTEP to address both near-term and longer-term objectives as described in Section 1.III.

The Draft Plan Appendix B, Table B.3-19 identifies the unresolved overloads associated with the Tesla–Newark alternatives. The City’s assessment uses CAISO’s final 2035 and 2040 GBA summer peak cases, applying the same P1 and P7 contingency definitions, with only project-specific topology changes necessary to reflect the Tesla–Trimble–Metcalf and WaNTEP configurations. Our assessment indicates that four (4) of the eleven (11) listed unresolved overloads also appear as overloaded under P1 or P7 contingencies, even with the Tesla–Trimble–Metcalf Project. In addition, three (3) facilities identified in Table B.3-19 do not show overloads under either normal or contingency conditions under any WaNTEP configurations.

Table 1 in the Appendix below summarizes the P1 and P7 facility-and-contingency combinations that remain unmitigated with the Tesla–Trimble–Metcalf Project. Table 2 documents the unresolved overloads referenced in Table B.3-19 that were not observed in the City’s power flow assessment. Table 3 shows that WaNTEP mitigates several P1 and P7 overloads across both the 115 kV and 230 kV systems, indicating that the project delivers incremental reliability improvements beyond those acknowledged in the CAISO’s documentation.

3. WaNTEP Was Not Designed to Resolve Downstream 115 kV Overloads
   
   CAISO’s evaluation observes that the studied WaNTEP configurations were not effective in addressing the identified overloads in the 115 kV grid downstream of the Newark substation.[4] The City believes this criticism conflates distinct planning objectives. WaNTEP was designed as a 230 kV system reinforcement to improve transfer capability and preserve optionality between Warnerville/Tesla and Newark; it was not intended to resolve all 115 kV network constraints downstream of Newark. Had CAISO studied WaNTEP in conjunction with similar downstream upgrades as those presumably addressed by the Tesla – Trimble – Metcalf Project, CAISO likely would find that the WaNTEP addresses both the near-term problems solved by Tesla – Trimble – Metcalf, while also addressing overloads on the 230 kV paths connecting to Newark, as noted in Appendix B of the Draft Plan.[5]

The City’s prior analysis shows that, while WaNTEP was not designed as a substitute for all downstream 115 kV reinforcements, its configurations nevertheless reduce loading and eliminate certain contingency overloads on key 115 kV facilities connected to Newark and multiple bay area 230kV import facilities. These effects allow CAISO to defer, right-size, or sequence downstream upgrades more efficiently, rather than committing prematurely to extensive local reinforcements.[6]

4. CAISO’s Cost Characterization of WaNTEP Overstates Its Incremental Cost

The City is concerned that CAISO’s characterization of WaNTEP as costing approximately $1.6–$2.1 billion is misleading. First, the $1.6–$2.1 billion capital cost estimates were for the HVDC line and converter station associated with the Tesla-Newark DC option, and not for the lower cost AC WaNTEP configuration.  Further, the costs also include the cost of several mitigations for facility overloads that are presumably unresolved by the Tesla-Newark HVDC option. Assigning the costs of unrelated downstream reinforcements to WaNTEP, without assigning similar costs to Tesla-Trimble-Metcalf and without crediting WaNTEP for resolving overloads on additional facilities, results in an inflated comparison with the Tesla–Trimble–Metcalf Project. The City is conducting additional power flow analysis to create a like-for-like comparison of the projects and will share its results with CAISO.

The City urges CAISO to remove the $50–$100 million cost of the Newark–NRS 230 kV line upgrade from the WaNTEP cost estimates. As shown in Table 2, several of the unresolved overloads referenced in the Draft Plan Appendix B, Table B.3-19 were not observed in the City’s power flow assessment; therefore, any associated mitigation costs included in the WaNTEP estimate should be removed from Appendix B.

For a fair cost comparison between the proposed Tesla–Trimble–Metcalf Project and WaNTEP, the City also urges CAISO to also allocate the cost of the unmitigated overloads listed in Table 1 of the appendix below to the Tesla–Trimble–Metcalf Project, which CAISO has already allocated to WaNTEP. Specifically, CAISO should include the facility costs for the following upgrades:

• $63–$126 million for the Hicks–Monta Vista 230 kV upgrade
• $60–$120 million for the Newark 230/115 kV transformer bank upgrade
• $50–$100 million for the Lone Tree–Cayetano 230 kV line upgrade

If the CAISO chooses to allocate the cost of $173–$346 million attributed to these upgrades to WaNTEP, then it should likewise add them to the Tesla–Trimble–Metcalf Project, as several P1 and P7 overloads remain unmitigated under that project.

5. Capital Cost Alone Is Not an Appropriate Basis for Comparison

The City emphasizes that this deferral and sequencing value represents a material ratepayer benefit that is not captured by gross capital cost comparisons alone, particularly when contrasted with extensive reconductoring or greenfield alternatives that carry greater delivery, permitting, and environmental risk.

The City further notes that comparing transmission alternatives solely on gross capital cost does not fully reflect their impact on CAISO ratepayers. Alternative ownership and financing structures, including full or partial public financing, result in significantly lower net ratepayer costs even where headline capital costs appear comparable. Accordingly, the City encourages CAISO to consider financing structure, cost recovery mechanisms, and long-term optionality, in addition to capital cost, when evaluating competing transmission solutions.

The City’s evaluation demonstrates that WaNTEP provides additional system-level reliability benefits that are unresolved by the Tesla-Trimble-Metcalf Project, and are not identified in the Draft Plan Appendix B. As shown in Table 3 in the Appendix below, WaNTEP mitigates several P1 and P7 overloads across both the 115 kV and 230 kV systems, indicating that the project delivers incremental reliability improvements beyond those acknowledged in the CAISO’s documentation. These findings demonstrate that WaNTEP offers additional reliability benefits should the CAISO Board approve the Tesla-Trimble-Metcalf Project under the 2025-2026 Transmission Plan.

6. Compressed Comment Timeline

The Draft Plan provides stakeholders with approximately two weeks to submit comments on several projects that have not been previously discussed in this cycle. This compressed timeline significantly limits the City’s ability to conduct a meaningful review or perform the level of impact analysis necessary to provide informed, technically grounded feedback. Additional time would materially improve the quality and usefulness of stakeholder input, particularly for newly introduced or substantially revised projects.

7. The City is Eager and Willing to Coordinate with CAISO Under FERC 2021 and Other Pathways for WaNTEP

The CAISO recognizes the potential benefits of upgrading the existing Warnerville-Newark transmission path to a higher capacity and has indicated an interest in working with Hetch Hetchy Water and Power on projects of mutual interest for the betterment of both CAISO and City’s systems.[7] The City reiterates its willingness to coordinate with CAISO regarding Hetch Hetchy Water and Power’s capital maintenance plans and to explore whether a coordinated, right-sized upgrade of the Warnerville–Newark corridor could be viable. Such coordination would be consistent with the Federal Energy Regulatory Commission’s 2021 policy encouraging voluntary agreements to plan and pay for transmission facilities that preserve optionality and provide long-term ratepayer benefits. The City looks forward to continued engagement with CAISO, both within and outside of  future planning cycles, to further evaluate Greater Bay Area transmission needs.

Appendix: 2035 & 2040 Summer Peak Reliability Assessment Results Tables

Table 1: P1&P7 Facility Overload and Contingency Combinations not mitigated with Tesla-Trimble-Metcalf in 2035 & 2040 GBA Summer Peak models

Table 2:Unresolved Overloads Referenced in Appendix B Table B.3-19 not observed in 2035 & 2040 Summer Peak models

Table 3: P1 & P7 Overloads Unresolved with Tesla-Trimble-Metcalf Project Addressed by WaNTEP in 2035 and 2040

[1] Draft Plan, pp. 69-70.

[2] Id.

[3] See the City and County of San Francisco Comments on 2025-2026 Transmission Planning Process Meeting 9/24 and 9/25 2025-2026 Transmission planning process, located at https://stakeholdercenter.caiso.com/Comments/AllComments/2CD110FD-8815-46B5-887A-FCF3E85603A2#org-feada347-0e01-4d33-9d00-77e0b0a51c78

[4] Appendix B to the Draft Plan, B-130.

[5] Id.

[6] City and County of San Francisco Comments on 2025-2026 Transmission Planning Process Meeting 9/24 and 9/25

2025-2026 Transmission planning process, located at https://stakeholdercenter.caiso.com/Comments/AllComments/2CD110FD-8815-46B5-887A-FCF3E85603A2#org-feada347-0e01-4d33-9d00-77e0b0a51c78

[7] Draft Plan, p.70.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

 No comments at this time.

3. Please provide your organization’s comments on the Economic Assessment.

 No comments at this time.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

 No comments at this time.

5. Please provide your organization’s comments on Frequency Response.

 No comments at this time.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

 No comments at this time.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

The Independent Energy Producers Association (IEPA) supports the Draft 2025-2026's Transmission Plan's prioritization of reliability-driven projects. As California expects an exorbitant increase in load, it is critical that our transmission system can deliver capacity where load is expected to grow the most. Prioritizing projects that provide capacity in locally constrained zones reduces pressure on our existing transmission system while we build out our system for the future.  

Resource Prioritization 

IEPA supports the focus on storage development paired with generation resources. IEP member companies participate in the Resource Adequacy (RA) market with storage hybrid resources, paired with solar, wind, and natural gas. Battery energy storage can be called upon for capacity where there is local constraint, increasing the total capacity of intermittent resources and replacing hours of natural gas peaker plants. Ensuring battery energy storage systems are prioritized for development in locally constrained regions lends itself to the development of hybrid resources. Newly added battery energy storage makes the most of existing resources that might otherwise be curtailed--like solar and wind--and reduce emissions of natural gas power plants that we continue to need for peaking purposes. With the approval of this draft plan, storage will handle much of the reliability hour concerns, hybrid resources will work to improve efficiency of existing resources, and natural gas will remain as the state's insurance resource during peak stress events.  

Transmission Project Prioritization 

IEP supports the draft plan’s focus on reducing congestion in the Bay Area, Central Valley, LA Basin, and San Diego County. California has worked hard to develop an abundant amount of renewable resources that struggle to reach high load zones that are growing every year. To ensure these resources contribute to meeting the increase in load, transmission projects along paths that export generation from major resource basins should be the priority. IEP is pleased to see these paths prioritized under the reliability driven projects in Table ES-1.  

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

IEP supports the inclusion of policy-driven projects that connect offshore wind resources. Offshore wind resources will be a necessary piece to California's relaibility portfolio. Although there have been federal setbacks, it is critical California continue to plan for these resources' development due to their long-lead development. 

3. Please provide your organization’s comments on the Economic Assessment.

As stated previously in the reliability-driven projects prompt, IEP is supportive of transmission development in the Bay Area, Central Valley, LA Basin, and San Diego County. IEP is especially thrilled to see the inclusion of Path 15 as a priority project due to congestion issues and deliverability potential from major resource basins.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

3. Please provide your organization’s comments on the Economic Assessment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

LS Power appreciates the opportunity to comment on CAISO’s 2025–2026 Draft Transmission Plan. With respect to the reliability-driven projects, we have brief comments on the Lugo 500 kV Reactive Power Reinforcement project, followed by substantive comments regarding the Manning 500 kV Auxiliary Collector Substation.

Lugo 500 kV Reactive Power Reinforcement project

LS Power respectfully requests that CAISO provide additional clarification regarding the eligibility of the Lugo 500 kV Reactive Power Reinforcement project (2526-R-21) for the Phase 3 competitive solicitation process. The identified scope consists +/- 300 MVAR of Statcom combined with three 200 MVAr switchable capacitor banks and represents a substantial transmission solution intended to mitigate low-voltage conditions and prevent post-transient voltage instability issues. Given the scale and capital intensity with significant ratepayer cost implications, LS Power believes it warrants careful consideration.  Section 24.5.1 of the CAISO Tariff requires that CAISO initiate a competitive solicitation process for Regional Transmission Facilities identified in the comprehensive Transmission Plan. The Tariff's overarching planning objectives, set forth in Sections 24.1 and 24.2, direct CAISO to identify transmission solutions in the most efficient and cost-effective manner. Assigning a project of this scale to the incumbent by default, without competitive proposals, is difficult to reconcile with the Tariff's cost-effectiveness mandate in Sections 24.1 and 24.2 and with FERC Order 1000's directive against undue incumbent TO preference in transmission planning. It is not apparent why this project would fall outside the Phase 3 competitive solicitation process. To the extent that there are efficiencies associated with co-locating the scope of this project with planned SCE facilities such savings should be realized through a proposal from SCE in the competitive process.

Manning 500 kV Auxiliary Collector Substation

LS Power respectfully requests that CAISO reconsider the Manning 500 kV Auxiliary Collector Substations LCRIF application and conditionally approve it in the Final Transmission Plan.

CAISO has indicated that the Manning LCRIF is not needed given the presence of existing transmission infrastructure in the area of the proposed facility.  While existing transmission infrastructure is present, the critical issue is that this infrastructure cannot be effectively accessed and utilized by the planned generation due to physical routing constraints that limit feasible interconnection pathways into the existing network. The Manning LCRIF addresses genuine transmission access constraints that prevent several gigawatts of renewable development from connecting to the grid, representing a coordinated infrastructure solution that individual generator interconnections cannot achieve at this scale and location.

The following comments reinforce why the Manning LCRIF represents critical infrastructure necessary to unlock California's renewable energy potential and support CAISO's transmission planning objectives.

1. Technical Necessity and Tariff Section 24.4.6.3 Compliance

LS Power anticipates that the Manning LCRIF will meet CAISO Tariff Section 24.4.6.3 requirements after CAISO conditional approval, given the demonstrated commercial interest discussed in Section 2 below. The CAISO conditional approval process will enable formal documentation of commercial commitments to satisfy final qualification criteria.

The need for this project is established through the technical necessity and commercial interest detailed in these comments and the original application. The Manning LCRIF meets the relevant criteria under CAISO Tariff Section 24.1.3.1(a) for LCRIF conditional approval: the project addresses genuine transmission access constraints, demonstrates significant commercial interest from multiple developers, and provides coordinated infrastructure solutions that individual generator interconnections cannot achieve at this scale and location. Existing transmission infrastructure cannot be accessed and utilized effectively by the planned generation due to physical routing constraints that limit feasible interconnection pathways into the existing network, as detailed in Section 3 below.

The project meets the tariff's criteria for demonstrated need, commercial interest foundation, and technical feasibility, providing a coordinated infrastructure solution that individual generator interconnections cannot achieve.

2. Demonstrated Commercial Interest and Project-Specific Need

Multiple established developers have executed letters of interest for the Manning LCRIF.  Given the confidential nature of the information contained in these letters of interest, they have been submitted to CAISO via the regionaltransmission@caiso.com email box. 

These letters demonstrate commercial need—developers cannot advance several gigawatts of renewable projects due to transmission access constraints preventing direct connection to existing Manning Substation infrastructure.

3. Critical Routing Corridor Congestion

The Manning 500/230 kV Substation faces critical physical constraints outside its property boundary: multiple 230 and 500 kV network lines already approved by CAISO, reservation of space for future network lines CAISO envisions, and planned generation and load interconnections have saturated available routing corridors. Building individual generation-tie lines per developer as part of the generation interconnection process is not an efficient or feasible way to accommodate the immense commercial interest and potential of the Manning area. Individual gen-tie facilities would be more expensive, more challenging to obtain environmental permits and real estate rights, create high upfront financing barriers for developers, and would not be feasible given the solar, battery storage, and load facilities all being planned immediately surrounding the Manning station.

4. Strategic Resource Area Designation

The Manning 500/230 kV Substation is surrounded by significant solar energy potential critical to California's long-term generation needs. The CPUC's proposed draft portfolios for the 2026-2027 Transmission Planning Process include over 44 GW of solar potential in the Fresno area alone. According to CAISO's RETI 2.0, the Manning 500/230 kV Substation lies within the Westlands SuperCREZ and San Joaquin Valley Transmission Assessment Focus Area (TAFA), where 5,000 MW of solar energy would be highly feasible. The initial Cluster 15 interconnection queue included approximately 25 requests totaling over 16,000 MW, with nine current active requests totaling approximately 4,000 MW, demonstrating strong commercial interest in this strategically important renewable energy resource area.

5. Alignment with CAISO Planning Objectives

The Manning LCRIF directly supports CAISO's transmission planning objectives by enabling orderly development of California's highest-value renewable resources. The approved Manning-Metcalf 500 kV line in the 2024-2025 TPP presents an immediate opportunity to accomplish both projects cost-effectively. The approved Manning-Metcalf line can terminate at the northern collector station, reducing the cost of that project. If the LCRIF is approved, LS Power can build the northern collector station and transmission line extension to the Manning substation. Savings from the reduction in scope of the Manning-Metcalf project can be applied to the collector station scope. This change in scope and responsibility can be memorialized in the Interconnection Agreement between LS Power and the Manning-Metcalf 500 kV project developer. This represents a cost-effective solution to address both project needs resulting in a timely and cost-effective connection hub for new generation interconnection in advance of completion of the Manning-Metcalf 500 kV project. 

Additionally, the eastern collector station presents strategic networking opportunities through the proposed Valley Clean Infrastructure Plan (VCIP). If VCIP components are approved in upcoming CAISO TPPs, the eastern Manning collector station could be networked through connection to the VCIP transmission system, transforming it from a radial LCRIF into a critical network transmission asset and significantly expanding interconnection capacity for the region.

The proposed LCRIF investment would unlock thousands of MW of renewable generation that cannot otherwise access the grid, providing exceptional value for ratepayers and advancing state clean energy goals. Absent approval of the Manning LCRIF, transmission already approved by CAISO may be underutilized.

Conclusion

While CAISO has indicated that the Manning LCRIF is not being recommended due to existing transmission infrastructure in the area, the need for this project is established through the demonstrated commercial interest and technical necessity outlined above. The critical distinction is between transmission infrastructure existing versus being effectively accessible and utilizable for planned renewable development. The project meets the relevant criteria under CAISO Tariff Sections 24.1.3.1(a) and 24.4.6.3 for conditional approval, addressing genuine transmission access barriers that prevent direct connection to existing Manning Substation infrastructure. With proven technical solutions and strong commercial commitments from multiple developers totaling several gigawatts, the Manning LCRIF presents immediate networking opportunities through Manning-Metcalf integration and future VCIP connectivity, transforming from radial facilities to critical network transmission assets. We respectfully request CAISO reconsider and conditionally approve this essential infrastructure project in the Final Transmission Plan. 

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

LS Power does not have comments at this time.

3. Please provide your organization’s comments on the Economic Assessment.

LS Power does not have comments at this time.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

LS Power does not have comments at this time.

5. Please provide your organization’s comments on Frequency Response.

LS Power does not have comments at this time.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

LS Power does not have comments at this time.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

LSA’s comments in this area are basically a follow-up to the 2024-2025 Transmission Plan and Cluster 15 initial interconnection studies, on an issue that does not appear to be addressed explicitly  in the draft 2025-2026 Transmission Plan.  Our concern is related to potential short-circuit duty (SCD) impacts of the numerous transmission upgrades recommended for approval in this planning cycle, and those approved in the last cycle as well. 

LSA and other developers expressed concerns last year that the SCD impacts for reliability-based upgrades in the last cycle were not addressed in the final transmission plan, producing base-case overloads for C15 projects and thus allocating, fully or partially, mitigation costs to those projects for which they may not be responsible.  In turn, this forced those C15 projects to post Commercial Readiness Deposits for those SCD upgrades.

In the final transmission plan for this cycle, the CAISO should address this issue, and clarify whether the TPP analyses here include SCD mitigation for reliability-based upgrades that:

• Were approved in the last planning cycle, so the studies can be updated, and cost responsibility for that mitigation can be removed from C15 projects in the upcoming Reassessment; and

• Are recommended for approval in this planning cycle, to avoid the same problems for Cluster 16 studies.

It makes much more sense to include required SCD mitigation in the same cycle as the upgrades causing them, and the draft Transmission Plan should be amended to include those SCD mitigation measures in the final plan, if they are not already accounted for.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

LSA has two comments on the Policy-driven Projects recommended for approval, related to the Trout Canyon-Lugo 500kV Line and cancellation of the Serrano-Del Amo-Mesa 500kV Transmission Reinforcement Project.  LSA supports the former but opposes the latter without consideration of additional upgrades.

Trout Canyon-Lugo 500kV Line:  LSA strongly supports inclusion of this project in the final 2025-2026 Transmission Plan.  This upgrade was recommended before by CAISO; for example, CAISO earlier identified this project as a potential solution for multiple constraints triggered by the 2024-25 TPP portfolio, and it was also noted in CAISO’s 20-Year Transmission Outlook as needed for future development.  This project would also presumably open up the East of Pisgah study area to new generation and storage projects in Cluster 16 and perhaps beyond that.

However, LSA is very concerned about the proposed 2035 in-service date for this upgrade.  The CPUC recently adopted a procurement order for resources needed to meet reliability needs by 2032 (see Decision Requiring 2029-2032 Electric Resource Procurement). The Trout Canyon-Lugo upgrade would resolve multiple constraints impacting projects that otherwise could meet the requirements in that procurement order, resulting in more supply and potentially lower resource costs to ratepayers.

It is unclear whether CAISO has performed a detailed analysis of  the Trout Canyon-Lugo development timeline, or if the proposed in-service date simply corresponds with the 2035 CPUC resource portfolio planning horizon.  LSA encourages CAISO to consider whether the proposed in-service date could be changed to 2032 to support the CPUC procurement order. This would send a signal to potential bidders to develop this line that the upgrade development timeline must be expedited to support the state's reliability and policy goals.

Cancellation of the Serrano-Del Amo-Mesa 500kV Transmission Reinforcement Project:  This cancellation apparently created the Mira Loma-Mesa area constraint (assuming this is the “Del Amo Project” cancellation referenced in the 2025 TPD Allocation Report) in the 2025-2026 TPD Allocation cycle.  That constraint resulted in zero TPD Allocations in wide swaths of the southern CAISO system, including the entire SDG&E area, even though there were apparently thousands of MWs of TPD available in several areas if not for that constraint.

In Section 3.3.2.2 of the draft 2025-2026 Transmission Plan, the CAISO states that this cancellation was motivated by SCE informing the CAISO that the original $1.125 billion cost of this upgrade had ballooned to over $5 billion, “with the significantly higher cost estimates resulting from increased requirements identified in the detailed engineering phase.”

The elimination of this apparently critically important upgrade warrants more than this cursory explanation.  At $5 billion, that would make it probably the most expensive transmission upgrade ever contemplated in the TPP.  The difference between $1.125 billion and $5 billion far exceeds the usual +/-50% cost ranges typically resolved through “detailed engineering.”

If not reversed, this decision is likely to result in zero new Cluster 16 projects seeking deliverability in the entire southern CAISO system, and zero new deliverable projects for years after that.  Moreover, Cluster 15 projects locating in areas where there appeared to be available deliverability may find that none is available for their upcoming TPD Allocation requests, leading to substantial future loss of projects in this cluster.

LSA urges the CAISO and SCE to: (1) explain the huge cost increase for this upgrade; (2) assess the impact to the very ambitious procurement goals identified by the CPUC and other Local Regulatory Authorities; and (3) explore other viable policy-driven upgrades in this cycle that could mitigate the huge negative impact of this cancellation.

3. Please provide your organization’s comments on the Economic Assessment.

LSA supports approval of the Gates-Los Banos #3 500 kV Line Series Compensation upgrade, to relieve the considerable Path 15 congestion that is estimated without it.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

LSA has no comments on this topic at this time.

5. Please provide your organization’s comments on Frequency Response.

LSA has no comments on this topic at this time.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

LSA’s comments in this section focus on proposed Transmission Plan Deliverability (TPD) reservations for Long-Lead-Time (LLT) resources, in Section 1.2.2.1 (Deliverability Reservations for Long Lead-Time Resources) of the draft transmission plan.  The table below compares proposed TPD reservations for this planning cycle to those from the last (2024-2025) planning cycle.

TPD RESERVATIONS 2025-2026 TPP vs. 2024-2025 TPP

CAISO is proposing to reserve nearly 13,000MW of deliverability, for 10-15 years, including on transmission approved for other purposes.  LSA also notes that at least one major offshore wind project (owned by Ocean Winds) has been canceled, and the future of others is uncertain, at best given the unfortunate hostility at the federal level to this technology, and clean energy generally.

As LSA has said before, we have significant concerns about CAISO’s actions to wall off large amounts of deliverability for favored technologies.  The adverse impact is magnified under the CAISO’s new Interconnection Request (IR) intake process, which limits capacity accepted for study based on available deliverability at each location.

LSA strongly believes that these reservations are unnecessary, since projects that they are intended to serve could be accommodated through the regular TPD Allocation process if LSEs were directed to execute PPAs with them earlier.  At a minimum, as detailed below, these reservations, and their impact, should be better explained; in addition, the new Geothermal reservation amounts and locations should be corrected or clarified.   

TPD Allocations:  The draft report states that “…some of this deliverability has already been allocated.”  The CAISO should distinguish between reservation amounts that have been allocated to projects in the queue using the TPD Allocation process applicable to all projects (and thus not of concern here) and those reserved for later, more speculative projects.

Reservation impacts:  The CAISO’s new IR intake process is highly dependent on TPD available at specific Points of Interconnection (POIs).  Developers need to know the locations where CAISO is constraining interconnections of, and TPD allocations to, non-favored resources.  TPD reservations at substations remote from load also reduce available TPD at substations between those points and load centers, since TPD is “deliverability to the aggregate of load.”  This will reduce the ability of projects with non-favored technologies to interconnect or obtain TPD Allocations at all of these intermediate substations, not just the outer locations where the TPD is reserved.

For example, TPD reservations “at” Palo Verde likely also constrain TPD (and future interconnections) downstream from there, at Colorado River, Redbluff, Devers, Valley, Alberhill, and other substations.  Likewise, TPD reservations at Diablo Canyon impact TPD and interconnections at Gates/Midway and POIs north, and also Midway/Vincent and POIs south.

The information in the final transmission plan should reflect the constraints imposed at all downstream substations, not just the substations where the reservations are “made.”

Geothermal Resources:  The information in the draft plan does not seem to follow the CPUC 2025-2026 TPP portfolio decision request to CAISO to reserve deliverability for specific resource types "using the amounts and locations included in the portfolio's busbar mapping results...". (See 557879249.PDF, p. 58).

The information provided in the current draft TPP, particularly for geothermal resources, is difficult to verify because it does not match up with the substation level data for geothermal resources provided in the CPUC's resource portfolio. LSA recommends the following improvements:

• Follow the same naming conventions as the CPUC TPP portfolio.  For example, the CAISO draft TPP shows that 40 MW should be reserved for "Geothermal (Corsac)".  The CPUC's resource portfolio does include 40 MW of geothermal, but it is shown at the "Summit" substation. It is not clear whether these resources are the same.

• Use the CPUC volumes for these resources, or explain why they do not. For example, the CAISO draft TPP indicates that 90 MWs should be reserved for Geothermal (Cape Station). The 90 MW number does not appear to be related to any of the Geothermal MWs identified in the CPUC's resource portfolio. CAISO should clarify how it arrived at the MWs identified in the deliverability reservations table. 

• Clarify the CAISO substation reservation location.  For example, Cape Station and Corsac do not appear to be CAISO substations, and the final plan should at least clarify the CAISO substation where the TPD is being reserved.

As an additional matter, the CAISO should be more forthcoming in the TPD Allocation Reports about the impact of these extensive transmission reservations.  For example, the description below from the 2025 TPD Allocation Report does not even mention TPD Reservations, and those impacts are not shown in the individual area analyses.  The CAISO should modify this report to include that information, and include it in future reports as well.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

n/a

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

NRDC is an international non-profit membership organization with more than 95,000 California members who have an interest in receiving affordable and equitable energy services while reducing the environmental impact of California’s energy use. As such, we support the identification of potential additional transmission needs outlined for Path 15 and Path 26 in the San Joaquin Valley area to support forthcoming clean energy projects.

We recognize the need to conduct additional studies prior to approving transmission projects in the region. As CAISO conducts these studies, we suggest they identify what would be necessary to concurrently address congestion and/or reliability issues along with infrastructure necessary to facilitate cost-effective integration of solar and storage in the region. We appreciate the staff’s work on these important matters and look forward to participating in next year’s TPP.

3. Please provide your organization’s comments on the Economic Assessment.

n/a

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

n/a

5. Please provide your organization’s comments on Frequency Response.

n/a

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

n/a

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

Please see NextEra Energy Resources comments below on CAISO's proposed cancellation of the Serrano-Del Amo-Mesa 500 kV project.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

NextEra Energy Resources applauds CAISO for recommending the Trout Canyon-Lugo 500 kV line for approval in the draft transmission plan.  As stated in previous comments, this line solves multiple constraints in the East of Pisgah area. CAISO’s alternatives analysis was rigorous and thoughtfully conducted. Four alternatives were thoroughly studied, and the Trout Canyon-Lugo 500 kV line was correctly found to be the best, and lowest cost alternative. Moreover, the cost estimates for the Trout Canyon-Lugo 500 kV line are based on multiple 500 kV line projects selected in CAISO’s Phase 3 process. CAISO has assessed this solution over four TPP cycles (since it was originally proposed in the 2022-2023 TPP cycle) and has reached a reasonable and defensible conclusion. The CAISO should include the line in the final transmission plan for Board approval.

Moving forward, developers need additional information to site projects and seek queue positions based on CAISO’s recommended approval of the Trout Canyon-Lugo 500 KV line. Accordingly, NextEra Energy Resources requests CAISO to publish in the final transmission plan the amount of Transmission Plan Deliverability (TPD) created by the line in the East of Pisgah and GridLiance West areas. Providing this information will help ensure the effectiveness of recent interconnection process enhancements by better aligning transmission planning and generator interconnection processes.  In addition, CAISO should clarify whether there are downstream constraints that may prevent the East of Pisgah study area from gaining meaningful TPD in the upcoming Cluster 16 study. According to the 2025 TPD Allocation Report, only a limited number points of interconnection (POIs) in the East of Pisgah study area can benefit from the new Trout Canyon-Lugo 500 kV line because most substations in East of Pisgah are still behind the Mira Loma-Mesa constraint.[1] Please see additional comments below requesting a CAISO-proposed solution in this TPP cycle to relieve this constraint.

Finally, NextEra Energy Resources notes that CAISO may wish to update the language in Appendix F (p.14) to acknowledge CPUC Decision (D.) 26-02-057, which later revised the CPUC’s request to CAISO. The Decision states: “In response to comments on the proposed decision, we are requesting that  CAISO allow in-CAISO transmission upgrades to be triggered by additional mapped out-of-state wind (1.5 GW of New Mexico wind and 1.5 GW of Wyoming wind) and the additional mapped out-of-state geothermal above the levels in the 2025-2026 TPP.”[2] Adding a reference to this latest decision will ensure the final transmission plan reflects CPUC’s current view.

3. Please provide your organization’s comments on the Economic Assessment.

NextEra Energy Resources appreciates CAISO’s comprehensive assessment of congestion along Path 15 and Path 26, including the evaluation of nineteen transmission alternatives to mitigate congestion on Path 15 alone. NextEra Energy Resources supports CAISO’s recommendation to add 70% series compensation on the Gates – Los Banos #3 line. This short-term solution will help balance the flow across the three 500 kV lines in the Path 15 corridor. In addition, NextEra Energy Resources supports CAISO’s confirmation of the need for new additional transmission on the 500 kV corridor in the San Joaquin Valley, encompassing the Path 15 corridor and portions of Path 26. One reasonable alternative is adding a new Windhub – Tesla 500 kV line that ties the Midway and Gates 500 kV substations. NextEra Energy Resources supports CAISO’s plan to seek Board of Governors’ approval and proceed with transmission reinforcement in the next TPP cycle.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

NextEra Energy Resources has no comments at this time.

5. Please provide your organization’s comments on Frequency Response.

NextEra Energy Resources has no comments at this time.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

NextEra Energy Resources respectfully requests CAISO to evaluate the consequences for existing queued projects associated with canceling the Serrano-Del Amo-Mesa 500 kV line, and identify and recommend an alternative solution for approval in this TPP cycle. According to the 2025 TPD Allocation Report, more than 10 GW of Cluster 14 and prior projects are behind the newly identified Mira Loma-Mesa constraint and will not receive TPD given the proposed cancelation of the Serrano-Del Amo-Mesa line.[3] In the SDG&E and SCE North of Lugo study area, significant amounts of TPD were originally available locally, but no project was awarded TPD due to the new Mira Loma-Mesa downstream constraint created by the cancelation of the Serrano-Del Amo-Mesa line. As a result, all Cluster 14 and prior projects behind the new constraint must be withdrawn or converted to Energy Only (EO) status. EO projects will not have another chance to seek TPD until their Commercial Online Date (COD), which significantly impairs their ability to secure off-takers, finance, and bring projects to market.  

From a statewide policy perspective, the proposed project cancelation will negatively impact the state’s ability to meet the CPUC’s Integrated Resource Plan (IRP) reliability mandates and California’s 2035 GHG goals. It potentially jeopardizes load-serving entities’ (LSEs) ability to comply with CPUC’s recent procurement order for 6,000 MWs Net Qualifying Capacity (NQC) (~20,000+ MW nameplate) of new resources. Cluster 14 and prior projects are the best candidates to reach COD in that timeframe. Yet 10,783 MW of those projects are behind the new Mira Loma-Mesa constraint.  According to NextEra Energy Resources’ analysis, a total of 61,000 MW of renewables or battery projects were designated as Full Capacity Deliverability Status (FCDS) in Cluster 14 and earlier queues. Thus, a non-trivial portion (~16%) of project MWs are affected by the proposed cancellation, leaving 50,000 MW nameplate before accounting for project attrition.  When fewer viable projects are available to compete for LSEs’ new resource solicitations, it harms ratepayers and runs counter to affordability objectives.

Looking ahead to Cluster 15 projects, more than 5 GW of active Cluster 15 projects located at Lugo, Mira Loma and Chino are being studied within FCDS zones and will be behind the new Mira Loma-Mesa constraint in the interconnection process. Back in November and December 2024, developers submitted projects at these locations based on CAISO’s constraint mapping spreadsheet showing 7,500 MW TPD availability in the SCE Metro study area. The constraint mapping spreadsheet was the main input CAISO used to identify the TPD zones and accepted queued positions based on competitive scoring up to 150% of available TPD. In December 2025, Cluster 15 projects made $ millions of additional monetary postings for their respective commercial readiness deposits and moved forward to the restudy phase based on the confirmation of TPD availability at these locations in the study report. However, the cancelation of this line would eliminate TPD for these projects, despite their competitive entry into the TPD zones, leaving developers with infeasible project risk. NextEra Energy Resources urges CAISO to ensure continuity in TPD availability throughout the interconnection process so that developers can make appropriate financial decisions at each decision point throughout the study process. Alternatively, CAISO should consider further Interconnection Process Enhancement (IPE) reforms that would allow developers a penalty-free withdrawal from their development security in such instances.

CAISO states that the recommended Mesa - Laguna Bell 230 kV #2 Upgrade project meets the needs anticipated in the 10-year planning horizon for the LA Basin area that were planned to be met by the Serrano–Del Amo–Mesa 500 kV Transmission Reinforcement project. The draft transmission plan states “In the Policy studies with the latest resource portfolios, the ISO determined that the project is not needed to ensure deliverability of resources” and that the CPUC IRP portfolio has 2,000 MW of additional battery storage downstream of the previously identified overloads that were driving the policy-driven need for the Serrano-Del Amo-Mesa  500 kV project. [4] Based on NextEra Energy Resources’ development experience, including an active project in the LA Basin, 2,000 MW is a highly unlikely assumption due to proximity to densely populated urban areas, high cost of land, public safety project setback issues, and other development constraints. Instead of relying on battery assumptions, CAISO should use its discretion approve another “wires” solution in this TPP cycle.

Turning to potential solutions, CAISO approved the Laguna Bell – Mesa #1 230 kV Line Rating Increase project and Mira Loma-Mesa 500 kV underground third cable upgrade with 3421 MVA normal rating in the 2022-2023 TPP cycle. However, Southern California Edison (SCE) said it could not achieve the intended normal rating at 3,421 MVA. Instead, the underground cable is still the limiting component with a 2,536 MVA normal rating. The TPD Allocation report results make clear that CAISO’s recommended approval of the Mesa – Laguna Bell 230 kV #2 230 kV upgrade in the draft transmission plan is insufficient to provide deliverability to policy-driven projects seeking to interconnect. Therefore, CAISO should consider approving in this TPP cycle a fourth underground cable to increase capacity to the originally intended normal rating (3,421 MVA). Given that the third cable reportedly costs approximately $35 million,[5] NextEra Energy Resources anticipates this will be the least-cost “wires” solution.

More broadly, this example points to a need for CAISO to further align transmission planning and interconnection processes. CAISO and CPUC have already made great strides through the Memorandum of Understanding to orchestrate the complex touchpoints between these processes, but there is clearly more to be done.[6] The recently reformed interconnection process is favorable to projects which happen to be located where TPD is initially allocated. But it provides no assurance that amount of TPD will be available once projects proceed to TPD studies, since much can change between projects entering the queue and becoming eligible to seek TPD.  In this instance, projects entered the queue based on TPD available from the Serrano-del Amo Mesa 500 kV project, and now, they will become stranded due to project cancellation.

The Serrano-Del Amo-Messa 500 kV line situation illustrates why a POI with TPD at the time of filing may not have TPD available once it's eligible for an allocation, and the same is true vice versa. Both are untenable for developers. NextEra Energy Resources recognizes that the TPP may not be the forum in which to make these changes, and that the Interconnection Process Enhancement (IPE) stakeholder initiative may need to take this up going forward.  In the meantime, NextEra Energy Resources respectfully requests CAISO to revisit the 2025 TPD Allocation report and consider issuing a revised report, once CAISO considers additional solutions (e.g., a fourth Mira Loma-Mesa underground cable) in the LA basin to address the Mira Loma-Mesa constraint in this TPP cycle. Due to the sizable impact on queued projects and the potentially deleterious effects on the CPUC procurement order and affordability objectives, we believe this is an unusual circumstance that merits consideration.

In summary, NextEra Energy Resources respectfully requests CAISO to:

• Include the Trout Canyon-Lugo 500 kV line in the final transmission plan for Board approval.
• Publish in the final transmission plan the amount of TPD created by the line in the East of Pisgah and GridLiance West study areas, and clarify whether there are downstream constraints that may prevent the East of Pisgah study area from gaining meaningful TPD in the upcoming Cluster 16 study.
• Evaluate the consequences for existing queued projects associated with canceling the Serrano-Del Amo-Mesa 500 kV line and identify and recommend for approval in this TPP cycle an alternative solution that preserves TPD allocation to queued projects upstream of the Mira Loma-Mesa 500 kV constraint. Specifically, CAISO should consider a fourth Mira Loma-Mesa 500 kV underground cable to increase capacity to the originally intended normal rating (3,421 MVA).
• Revisit the 2025 TPD Allocation report and consider issuing a revised report, once CAISO considers additional “wires” solutions in the LA Basin to address the Mira Loma-Mesa 500 kV constraint in this TPP cycle.

[1] 2025 Transmission Plan Deliverability Allocation Report, pp. 48-53.

[2] D.26-02-057, p. 71

[3] 2025 Transmission Plan Deliverability Allocation Report, pp. 48-53.

[4] 2025-2026 Draft Transmission Plan, p. 109.

[5] CAISO Board-Approved 2022-2023 Transmission Plan, p. 90.

[6] Memorandum of Understanding between CPUC, CEC, and CAISO regarding Transmission and Resource Planning and Implementation, December 2022.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

No comments at this time.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

No comments at this time.

3. Please provide your organization’s comments on the Economic Assessment.

No comments at this time.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

No comments at this time.

5. Please provide your organization’s comments on Frequency Response.

No comments at this time.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

NCPA appreciates the opportunity to provide comments on the 25-26 Draft Transmission Plan. NCPA further appreciates CAISO’s commitment to meet system needs with upgrades that are the “most efficient[] and cost-effective[].” Draft Transmission Plan Page 1. This commitment is especially important as CAISO has approved over $26 billion worth of TPP projects since 2022:

Source: BAMx, based on CAISO TPP data

CAISO’s 20-Year Outlook estimated $45.8 to $63.2 billion in transmission spending between 2025 and 2045. Over just the first two of these years, the CAISO has proposed almost $12 billion in spending on transmission upgrades. NCPA is concerned that a significant portion of this transmission spending is associated with load forecasts based on speculative data center demand and long lead-time resources that may not materialize. NCPA urges the CAISO to focus on cost containment and encourages the CAISO to mitigate risk. To do so, NCPA asks the CAISO to:

• Regularly reassess the need for previously approved TPP projects. Because recent transmission plans have assumed speculative load growth and significant long lead-time resources, the CAISO should reconsider approved transmission spending if the load growth or resource does not materialize. For example, NCPA appreciates the CAISO’s reassessment and cancelation of the Del Amo – Mesa – Serrano 500 kV project due to cost increases. Draft Transmission Plan Page 11.
• Establish clear rules and requirements to determine when the long lead-time deliverability reservations should be released. In the current political environment, there is considerable risk faced by resource developers, particularly offshore wind development. While NCPA does not object to long lead-time resources deferring first attempts to seek TPD, the CAISO should be able to determine when a resource is no longer feasible for development. If that determination is made, the CAISO should release TPD to the market for the purpose of interconnecting alternative projects. Whether these determinations are based on defined timelines (e.g., if the project is delayed beyond an expected COD) or tied to key regulatory changes that result in the project no longer being viable, it will be necessary to make these determinations to ensure that infeasible projects do not linger in the queue holding valuable TPD that could be used by other interconnection customers. Regularly reviewing and releasing reserved TPD that is no longer need may also help avoid additional costly transmission upgrades driven by planned resource additions.
• Continue to consider the resource plans of non-CPUC local regulatory authorities. Considering the resource needs and load forecasts of all LRAs, including non-CPUC LRAs like NCPA’s members, ensures that the CAISO is planning its system using complete and accurate information.
• Explore cost allocation to other entities or ratepayers. This transmission plan includes significant spending to deliver out-of-state resources to CAISO ratepayers. The CAISO should explore Subscriber PTO solutions for these resources to the extent possible. Further, these transmission solutions likely benefit ratepayers outside of the CAISO footprint and the CAISO should explore splitting cost responsibility with those other ratepayers. One example of this arrangement is the cost-splitting agreement the CAISO entered into with Idaho Power for the SWIP-North Project. It is NCPA’s understanding that these cost allocation methodologies are only explored for projects that are not approved in the transmission plan – NCPA encourages the CAISO to investigate these options for projects that are approved in the transmission plan to the extent possible.
• Undertake a review of the competitive solicitation process. NCPA appreciates the CAISO’s use of the competitive solicitation process to attempt to lower costs to ratepayers. But given recent issues with project cost containment commitments (see, e.g. DCRT’s request for recovery of more than double its project cost cap in its FERC rate case), NCPA is concerned that the competitive solicitation process is not working to contain costs as intended and requests that the CAISO undertake a comprehensive review of the process.
  • Enforcement of cost containment commitments.  The CAISO has selected billions of dollars-worth of projects for competitive solicitation and the project sponsors are often selected based on the strength of their cost containment commitments, which may include project cost and/or revenue requirement caps that are purportedly lower than the project costs that would result if the incumbent TOs built these projects. But these cost containment commitments are illusory if the CAISO does not meaningfully enforce the commitments, both during the project development process and the rate recovery process at FERC. If the CAISO cannot commit to strict and meaningful enforcement of the cost containment commitments, the CAISO should not submit more projects for competitive solicitation.
  • Transparency. The competitive solicitation process increases the number of CAISO PTOs and thus increases the effort required by ratepayer-side parties to ensure that the rates being charged by these CAISO PTOs are just and reasonable and consistent with the cost-containment commitments. To make this review easier on ratepayer-side parties, like NCPA, the CAISO should require competitive developers to include transparency mechanisms in their rates which clearly demonstrate adherence to cost containment commitments.[1] The CAISO should also require developers provide APSAs, APSA amendments, and final cost reports to ratepayer-side parties, which would allow them to understand why some developers may have costs that are greater than their publicly available cost containment commitments.[2]

[1] For example, NCPA challenged Viridon California’s initial formula rate filing (in FERC Docket No. ER24-766) because it was not clear how Viridon’s proposed formula rate template could transparently accommodate cost containment commitments. Viridon California has since been selected for two projects potentially worth over $4 billion.

[2] For example, in response to data requests and informal challenges from ratepayer-side parties, including NCPA, LS Power has provided information on the implementation of its cost containment commitments which explains the difference between costs included in LS Power’s formula rates and the cost commitments noted in the public project selection reports. NCPA appreciates LS Power’s responsiveness to our requests and the transparency of its formula rates.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

3. Please provide your organization’s comments on the Economic Assessment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

The Policy Assessment notes that the 2025 – 2026 TPP base case portfolio mapped significant amounts of geothermal to IID and areas in Nevada and Utah beyond the CAISO’s Balancing Area. Furthermore, staff identified these resources as requiring MIC expansions. (Appendix F, p. 15)

The CAISO recognizes that MIC expansions are required to bring out of state geothermal resources into the CAISO. As such, Ormat would appreciate further detailed clarification on how the CAISO assessed where these MIC Expansions should occur for geothermal resources. NVE’s Silver Peak Substation has the potential to bring at least 120 MW of Central Nevada geothermal resources into CAISO via the Control 115 kV substation. Significant commercial interest exists at Control; however, transmission constraints hinder future development. Moreover, SCE’s Ivanpah-Control Transmission Line Rating Remediation project is anticipated to increase power flows by 50%.[1] As such, Ormat requests additional clarification from CAISO regarding whether consideration was given to expanding this project to accommodate further MIC expansion; and, if so, comment on the economic feasibility or benefit-cost ratio of such a project.

[1] https://ia.cpuc.ca.gov/environment/info/aspen/ivanpah-control/factsheet.pdf

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

During the Stakeholder call, CAISO staff noted that the Control – Inyokern line was not overloaded in the modeled base case portfolio. Ormat is concerned that this conclusion appears fundamentally at odds with the historical performance of the Control – Inyokern corridor. Resources in the Control area have experienced frequent curtailment, including approximately 140,000 MWh of geothermal resources in 2025.  This curtailment strongly suggests that transmission limitations remain unresolved in practice.

Furthermore, in its 2025–2026 busbar mapping, the CPUC estimated that the Control to Inyokern area constraint had a high likelihood of being triggered.[1] Considering these historically observed outcomes, Ormat requests that CAISO verify that its base case accurately reflects the resources interconnected at Control and specifically explain why the modeled results differ so markedly from the persistent congestion and curtailment observed during actual operations.

[1]  Compact Dashboard for the PD 25-26 TPP Base Case “2035_Exceedance_Summary” and “2040_Exceedance_Summary” tabs

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

Pacific Gas and Electric Company (PG&E) appreciates the opportunity to provide comments on the California Independent System Operator’s (CAISO) 2025-2026 Draft Transmission Plan (Draft Transmission Plan). PG&E also appreciates CAISO’s continued leadership in transmission planning and development, and its efforts to identify cost-effective solutions needed to reliably serve customers across California.

Based on state energy demand forecasts, CAISO’s Draft Transmission Plan identifies reliability projects that will help ensure load-serving entities can continue to reliably serve customers while advancing the State’s long-term building and transportation electrification goals. PG&E remains focused on helping build the most economically resilient energy system for California and its customers and appreciates CAISO’s work to develop a transmission plan that supports reliability, affordability, and the clean energy transition.

PG&E generally supports the Draft Transmission Plan and the reliability-driven projects recommended for approval in PG&E’s service area, including the Tesla-Trimble-Metcalf 230 kV Corridor Expansion project (“Tesla-Trimble-Metcalf Project”). Upgrades such as the Tesla-Trimble-Metcalf Project will help ensure PG&E can continue to reliably serve its customers at the lowest reasonable cost based on the energy demand forecasts and support achievement of the State’s long-term clean energy goals.

Tesla-Trimble-Metcalf Existing Corridor Expansion Project

PG&E supports the CAISO’s approval of the Tesla–Trimble–Metcalf 230 kV Corridor Expansion project. To solve the reliability problems identified by the CAISO in the San Jose/South Bay area, the Tesla-Trimble-Metcalf Project is the superior solution among the proposed alternatives because it effectively provides multiple new sources directly into the South Bay load pocket while maximizing existing rights-of-ways in a cost-effective manner. The Tesla-Trimble-Metcalf Project is designed to meet all applicable North American Electric Reliability Corporation (NERC) reliability criteria and to serve future system needs as demand is forecasted to grow significantly in the South Bay due to transportation electrification, building decarbonization, and the siting of large new loads.

PG&E recognizes how crucial this project is for meeting the region’s rapidly accelerating Bay Area load growth and import capacity requirements, and PG&E appreciates CAISO staff’s dedication and leadership throughout this process to identify the right solution.

The Tesla-Trimble-Metcalf Project is designed to directly address fast-paced and geographically concentrated new loads in the Bay Area – driven by electrification, significant customer additions, and shifts in resource availability. By leveraging existing 230 kV transmission corridors and substations and reinforcing existing infrastructure, the project delivers substantial incremental transfer capability while aligning with practical implementation objectives. Reinforcing the Tesla-Trimble-Metcalf 230 kV corridor will substantially increase import capability into critical load pockets, alleviate overloads on constrained 230?kV and 115?kV facilities, and enhance operational flexibility.

The Trimble Project delivers significant import capability, amounting to multiple gigawatts of combined transfer capacity. By strengthening the backbone of the South Bay transmission system, the project positions the grid to reliably serve expanding future demand. Moving forward with this project reflects a forward-looking planning approach that anticipates long-term system needs, rather than relying solely on incremental upgrades.

PG&E also appreciates that CAISO identified an innovative solution in the Tesla-Trimble-Metcalf Project and modified or reduced the scope of previously approved transmission plan elements to reflect and enable the improved value delivered by this project. Given the continued increase in forecasted load growth, PG&E is ready to work closely with CAISO to ensure the Tesla-Trimble-Metcalf Project advances through approval and execution consistent with the CAISO Transmission Planning Process (TPP).

City and County of San Francisco Warnerville-Newark Transmission Expansion Project

PG&E appreciates the CAISO evaluating and performing diligence on the City and County of Francisco’s (CCSF) Warnerville–Newark Transmission Expansion Project (WaNTEP) over the last two transmission planning cycles. In the Draft Transmission Plan, CAISO again is not recommending approval of the WaNTEP proposal to meet the reliability needs identified due to identifying a solution that more adequately addresses the reliability need. The Draft Transmission Plan further states that CAISO plans to coordinate with CCSF regarding its capital maintenance plans and investigate whether a coordinated arrangement could preserve future optionality, including in light of CCSF’s stated need to rebuild its aging transmission assets.

If CAISO elects to pursue further engagement with CCSF regarding WaNTEP, PG&E seeks greater clarity on how CAISO intends to ensure appropriate operational control, entitlement allocation, and long-term accountability if any facilities associated with a WaNTEP-based solution are not transferred to CAISO operational control. Given CCSF’s current status outside the CAISO PTO framework, PG&E believes it is important that any approval of the WaNTEP proposal clearly demonstrate that the project’s scope, governance structure, and cost allocation are fully aligned with CAISO tariff principles and deliver clearly quantified net benefits to existing CAISO customers.

PG&E encourages CAISO to apply appropriate guardrails and transparency to any discussions or negotiated arrangements associated with WaNTEP.  In PG&E’s view, any approved solution should be consistent with stakeholder expectations, minimize customer risk, and support fair and durable transmission planning outcomes.

PG&E’s Endorsement of CAISO’s Proactive Planning for Greater Bay Area Load Growth

PG&E appreciates and supports the CAISO’s proactive approach in the 2025–2026 transmission planning process to planning for Greater Bay Area load growth and identifying the potential need for additional transmission expansion to support rapidly changing load conditions. As Greater Bay Area electrification, large load growth, and transportation-related load continue to accelerate, reliance on constrained corridors, such as the Metcalf–Manning corridor and transmission paths in the southern portion of PG&E’s system, is expected to increase. PG&E considers CAISO’s proactive planning strategy vital to maintaining reliable and affordable electric service as regional demand evolves.

PG&E supports CAISO’s continued evaluation of structural solutions - such as a potential new Windhub–Tesla 500 kV line – that can complement incremental upgrades by creating more robust import capability into the PG&E Greater Bay Area under high-load and high-import conditions. This forward-looking planning approach strengthens transmission system resilience and supports the integration of diverse resources needed to serve future electricity demand.  PG&E looks forward to continuing to support the CAISO through technical collaboration and study development to advance both near-term and long-term solutions that address congestion, import capability, and load-serving needs.

Large Load interconnection and Coordinated Response to Import and Local Network Constraints

In addition to the area-wide planning the CAISO performs through the transmission planning process, PG&E appreciates CAISO’s use of the concurrence process to address local network needs associated with large load interconnections. PG&E also appreciates CAISO’s diligence in reviewing and providing concurrence on PG&E projects submitted through the load concurrence process. CAISO’s concurrence process is critical to enabling large load projects to come online in a timely manner to serve retail customers. The process provides important validation of the assumptions used in planning and confirms that proposed projects do not create adverse reliability impacts to the regional system, and helps ensure that new infrastructure is appropriately sized, timed, and initiated based on credible and coordinated planning to meet forecasted load growth.

PG&E further commends CAISO for its structured process to address regional import constraints associated with large load interconnections while maintaining system-wide reliability. CAISO’s planning framework appropriately identifies and mitigates regional area-wide transmission and intertie impacts driven by significant new load growth. In parallel, PG&E continues to advance the local and interconnection-driven network upgrades needed to reliably serve retail customers and safely integrate new large loads under its obligation to serve them. This coordinated division of responsibility - CAISO addressing regional, area-wide impacts and the PTO advancing local network reinforcements – is critical to supporting timely load interconnection without overreliance on operational workarounds.

As large load interconnections potentially continue to accelerate across the system, PG&E supports continued alignment between CAISO and PTO planning efforts to ensure reliable, efficient, and coordinated outcomes for customers and the grid.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

Consideration of Northern California Import Pathways

In the Draft Transmission Plan, the CAISO recommends approval of the Trout Canyon–Lugo 500?kV transmission line to expand the capability to import out-of-state resources from Nevada into Southern California. PG&E understands that the CAISO identified the need for this project based on California Public Utilities Commission (CPUC)-provided Integrated Resource Plan (IRP) portfolios to ensure adequate transfer capacity to integrate renewable resources and support achievement of the State’s clean energy goals.

While PG&E appreciates the CAISO’s need to identify and approve the Trout Canyon–Lugo project based on the CPUC-provided portfolios, PG&E also notes that, over the last several TPP cycles, the CAISO has approved or acquired multiple out-of-state transmission projects that access resources outside the CAISO footprint through Southern California and Southern Nevada interties, including SWIP-North, SunZia and TransWest Express. Collectively, these projects expand import capability through CAISO’s southern interties and make delivery to PG&E’s service area dependent on Path 15 and Path 26 availability, which reinforces the importance of evaluating the geographic diversity and balance of future interregional transmission development.

Looking ahead to the 2026–2027 TPP, PG&E encourages the CAISO to evaluate whether development of a new direct import pathway into Northern California may be necessary to meet the State’s long-term clean energy goals while providing additional reliability and resiliency benefits. In particular, a northern import solution not only could help ensure that future incremental congestion on Path 26 and Path 15 does not constrain delivery of out-of-state energy supplies needed to serve load within PG&E’s service territory, but it could also help reduce the congestion on these two paths.

Long-range planning efforts and reports – including CAISO’s 20-Year Transmission Outlook Update, the Deptartment of Energy’s 2024 National Transmission Planning Study, and western-wide studies such as the WestTEC analysis – have highlighted the growing need for increased transfer capability, including the potential benefits associated with more direct delivery, between the Mountain Region and Northern California. PG&E believes that proactively evaluating these options in future planning cycles would complement recent southern-focused interregional investments and support a more resilient, flexible, and geographically balanced transmission system for California.

PG&E looks forward to continued engagement with CAISO on long-term import transmission needs as part of next years and subsequent transmission planning cycles.

3. Please provide your organization’s comments on the Economic Assessment.

Near-Term and Long-Term Solutions for Path 15 and Path 26 Congestion: 

PG&E appreciates the CAISO’s evaluation of congestion on Path 15 and Path 26 and its identification of both near-term and longer-term approaches to address emerging south-to-north transfer constraints.

PG&E supports the Los Banos–Gates No. 3 500?kV series compensation project as an interim solution to help mitigate congestion on Path 15. PG&E looks forward to continued coordination with the CAISO to support any additional studies needed to confirm appropriate application of series compensation. PG&E further supports engagement among impacted parties, including the CAISO, PTOs, and the Western Area Power Administration, to refine the scope and identify the optimal location for series compensation to ensure the solution is technically sound and minimizes unintended system impacts.

PG&E also supports the CAISO’s identification in the Draft Transmission Plan of the need for a longer-term solution to address persistent south-north congestion on Path 15 and Path 26. PG&E agrees with the CAISO’s approach to further evaluate and finalize a long-term solution in the 2026–2027 TPP, rather than rushing approval in the current cycle. PG&E believes this approach allows for the necessary analytical rigor and scenario evaluation to ensure the most effective and durable solution is identified, including potential options such as a Tesla–Windhub 500?kV transmission project.

As the CAISO advances these longer-term evaluations, PG&E encourages continued coordination with all impacted transmission owners to ensure that any associated system impacts – both regional and local – are identified and addressed as part of project scoping and development.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

Primergy appreciates the opportunity to provide comments in support of the Trout Canyon–Lugo (TC–Lugo) 500 kV project and believes it should proceed in the TPP process. The Trout Canyon–Lugo project will be helpful in mitigating grid constraints and bringing additional capacity to CAISO.

The integration of the 3GW of planned capacity at Trout Canyon through the completion of the project will address critical reliability issues at key locations. The project is a proactive, comprehensive solution that will support a broad range of resource planning scenarios and will allow for additional flexibility in energy portfolios.

Additionally, the project will allow significant amounts of renewables and storage to be deliverable to CAISO and support meeting California’s targets for renewable energy procurement. It will also provide additive support towards future clean energy developments in the area.

Primergy believes the GLW expedited process is the best path forward to enable the earliest construction of the TC-Lugo project and the completion of energy projects within CAISO.

Regards,

Primergy

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

Primergy appreciates the opportunity to provide comments in support of the Trout Canyon–Lugo (TC–Lugo) 500 kV project and believes it should proceed in the TPP process. The Trout Canyon–Lugo project will be helpful in mitigating grid constraints and bringing additional capacity to CAISO.

The integration of the 3GW of planned capacity at Trout Canyon through the completion of the project will address critical reliability issues at key locations. The project is a proactive, comprehensive solution that will support a broad range of resource planning scenarios and will allow for additional flexibility in energy portfolios.

Additionally, the project will allow significant amounts of renewables and storage to be deliverable to CAISO and support meeting California’s targets for renewable energy procurement. It will also provide additive support towards future clean energy developments in the area.

Primergy believes the GLW expedited process is the best path forward to enable the earliest construction of the TC-Lugo project and the completion of energy projects within CAISO.

Regards,

Primergy

3. Please provide your organization’s comments on the Economic Assessment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

Santa Clarita Valley Water Agency (SCV Water) requests that CAISO provide, or clearly identify how stakeholders may obtain the specific models used in the studies underlying Appendix F. Based on SCV Water’s review, the models currently available online do not appear to match the generation depicted in Figures F.8-1 and F.8-2 (Appendix F, p. 88).  SCV Water is unable to identify the 2035 and 2040 Greater Fresno Interconnection Area models corresponding to those figures. While 2035 and 2040 Bulk Case models appear to be available on the portal, these cases do not appear to include the additional generation shown in the figures. Without access to the actual study, stakeholders have limited ability to evaluate the contributing factors driving the constraints in this interconnection area or to assess why certain facilities were not identified for upgrade. Providing access to those materials would support a more informed review of key study assumptions and would help stakeholders develop more detailed insight into the transmission elements and generation patterns contributing to observed stress around relevant constraints.

3. Please provide your organization’s comments on the Economic Assessment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

Given CAISO-modeled overloads on Gates 500/230 kV TB 11 (Appendix F, p. 96), SCV Water would expect CAISO to pursue cost-effective upgrades to these transformers to improve the overall deliverability in the Greater Fresno Interconnection Area, rather than assuming batteries are providing deliverability through charging. However, during the April 15, 2026, stakeholder call, CAISO stated that the Gates 500/230 kV Transformer Banks #11 & #12 constraints were not triggered in the baseline portfolio. SCV Water noted that the 2040 Off-Peak deliverability constraints in Table F.8-15 included 135.87% line loading at Gates 500/230 kV TB 11. The constraint was listed as causing 906 MW of renewable curtailment without mitigation and listed, “Dispatch 1180 MW portfolio battery resources in charging mode” as a potential mitigation. (Appendix F, p. 96)

SCV Water recognizes the CAISO’s proposed mitigation may be cost-effective in the near term by avoiding additional upgrades. Nevertheless, because the CAISO’s 2025-2026 busbar mapping indicated that upgrading the Gates 500/230 kV Transformer Bank could increase transmission capability by over 10 GW at an estimated cost of $35 million, SCV Water suggests that performing this upgrade could offer a more resilient transmission system in the Fresno Area.[1] Moreover, while SCV Water recognizes the 2026 – 2027 Transmission Plan is outside the scope of the 2025 – 2026 TPP, looking ahead to the CPUC’s 2026 – 2027 busbar mapping indicates that the same Gates 500/230 kV TB 11 constraint is triggered as early as 2036. Therefore, the Gates 500/230 kV Transformer Bank upgrade could offer a more robust mitigation to this constraint.

Furthermore, SCV Water is very concerned that CAISO is relying on battery storage charging as a deliverability service. Over 9,400 MW of renewable generation are mapped behind this Gates constraint. (Appendix F, p. 96) Such significant quantities of solar generation will be required to meet California’s decarbonization goals; however, absent the creation of incremental deliverability, these resources will not be built.  Although batteries enable greater solar generation, SCV Water fears that without upgrades to transmission infrastructure, incremental deliverability will not be created in the Greater Fresno Interconnection Area.  SCV Water urges CAISO to more closely consider transmission-based solutions, such as the Gates 500/230 kV Transformer Bank upgrade, which CPUC’s busbar mapping suggests will create the deliverability needed to support California’s clean energy goals.

Finally, SCV Water observed a similar pattern of accelerated constraint triggering at the Mustang-Henrietta 230 kV line constraint. Specifically, this constraint was highlighted in CPUC’s 2025 – 2026 busbar mapping as high likelihood of being triggered in 2040 but occurs as early as 2036 in the 2026 – 2027 busbar mapping. Although the Mustang-Henrietta 230 kV line constraint was not triggered in the baseline portfolio, SCV Water respectfully requests similar consideration be given to the Mustang-Henrietta 230 kV line upgrade as applicable.

[1] Compact-Dashboard_25-26TPP_BaseCaseD_2025-02-20 at “2040_Exceedance_Summary” tab.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

I. Introduction and Requested Action

The City of Santa Clara, dba Silicon Valley Power (“SVP”), submits these comments in response to the California Independent System Operator Corporation (“CAISO”) 2025–2026 Draft Transmission Plan (“Draft Plan”) and materials presented at the April 15, 2026 stakeholder meeting.

SVP requests that the CAISO:

1. Place the South Bay Reinforcement Project (Revised Scope) and De Anza 115 kV Substation projects on hold pending SVP’s evaluation of their impacts on SVP’s system; and
2. Defer action on the Tesla–Trimble–Metcalf 230 kV Corridor Expansion project pending completion of that evaluation.

These requests are necessary because the Draft Plan includes material, previously undisclosed reconfigurations of SVP’s transmission interties that were not subject to prior notice, discussion, or Affected System coordination.

II. Draft Plan Characterization of Intertie Reconfigurations

The Draft Plan includes transmission projects in the South Bay area that would modify SVP’s existing 115 kV transmission interties as follows:

• NRS–Nortech 115 kV Line: relocation of the line’s terminal point from Nortech Substation to the proposed De Anza 115 kV Substation (De Anza 115 kV Substation project).
• KRS–FMC 115 kV Line: relocation of the line’s terminal point from FMC Substation to Trimble Substation (South Bay Reinforcement Project – Revised Scope).

These modifications constitute topological reconfiguration of SVP’s transmission interface, rather than incremental facility upgrades.

SVP was not notified of these changes prior to issuance of the Draft Plan, and they were not presented or discussed in prior stakeholder materials during this Transmission Planning Process cycle.

III. Reliability Implications

The intertie reconfigurations described above may materially affect SVP’s ability to reliably import power under N-1 and N-1-1 contingency conditions, particularly in the context of rapid load growth in the South Bay. The affected facilities represent critical import paths into SVP’s system.  Relocation of terminal points and associated network reconfiguration may materially alter:

• contingency power flow distribution across the South Bay interface
• thermal loading of SVP import facilities under stressed system conditions
• import capability during peak demand periods
• interaction with existing transmission constraints in SVP’s system

SVP previously identified in its October 9, 2025 comments on CAISO’s preliminary reliability assessment that key import facilities, including the Newark–NRS 115 kV and NRS–SRS 115 kV lines, exhibit contingency overload sensitivity and are highly dependent on transmission topology. The reconfigurations included in the Draft Plan have not been evaluated in coordination with SVP, despite their direct relevance to these previously identified conditions.

IV. Affected System Coordination and Planning Process Consistency

In prior Transmission Planning Process cycles, CAISO engaged SVP in Affected System coordination when proposed transmission solutions materially impacted SVP interties or import facilities. That coordination enabled SVP to evaluate system impacts prior to project recommendation. No comparable Affected System coordination occurred in this cycle, notwithstanding the inclusion of intertie reconfigurations that directly affect SVP’s transmission interface.

As a result, SVP has not had an opportunity to evaluate:

• the reliability impacts of the proposed reconfigurations
• their interaction with SVP’s existing constraints
• their effect on import capability under contingency conditions

V. Stakeholder Process Timing and Record Development

The CAISO stakeholder process timeline provided less than three weeks for stakeholder review of newly identified transmission reconfigurations affecting SVP.

This timeframe was insufficient to evaluate:

• N-1 and N-1-1 contingency performance impacts
• topology-driven changes in power flow behavior
• import constraint implications under rapidly growing South Bay load conditions
• interactions with existing South Bay reliability limitations

Given the system sensitivity involved, the stakeholder process timeline did not provide a reasonable opportunity for SVP to perform the necessary Affected System analysis.

This limitation was compounded by the fact that the CAISO-recommended projects were not identified or discussed in any prior stakeholder materials or meetings during this Transmission Planning Process cycle, depriving affected parties of the opportunity to engage earlier in the development of potential solutions. SVP engaged with CAISO multiple times during this planning cycle, including direct discussions at CAISO offices, yet these intertie reconfigurations were not identified or raised for coordination. 

Under these circumstances, the stakeholder process did not provide the level of transparency, coordination, or opportunity for meaningful input expected for transmission projects affecting adjacent systems.

Approval of projects incorporating unreviewed transmission interface reconfigurations under these conditions would establish a precedent for advancing material topology changes without affected-system validation, increasing the risk of unanticipated reliability impacts and subsequent need for corrective action.

VI. Requested Action

For the reasons described above, SVP respectfully requests that the CAISO:

1. Place the South Bay Reinforcement Project (Revised Scope) and De Anza 115 kV Substation projects on hold pending Affected System review in coordination with SVP; and
2. Defer action on the Tesla–Trimble–Metcalf 230 kV Corridor Expansion project pending completion of SVP’s evaluation, given its interaction with the same South Bay transmission corridors and the unresolved impacts associated with the intertie reconfigurations described above.

Deferral of the Tesla–Trimble–Metcalf project is necessary to ensure that its effects on SVP’s system are evaluated in conjunction with the proposed intertie reconfigurations, consistent with Transmission Planning Process requirements for coordinated system review.

Deferring approval under these circumstances is consistent with maintaining the integrity of the Transmission Planning Process and ensuring that transmission solutions are based on fully evaluated and coordinated system configurations.

SVP will submit supplemental technical comments following completion of its preliminary system impact assessment.

VII. Conclusion

SVP supports transmission investments that enhance reliability in the South Bay and enable continued economic growth. However, inclusion of material transmission interface reconfigurations without prior identification or Affected System coordination is inconsistent with sound transmission planning practice.

SVP requests that CAISO ensure Affected System coordination is completed prior to further action on the identified projects.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

No comment.

3. Please provide your organization’s comments on the Economic Assessment.

No comment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

No comment.

5. Please provide your organization’s comments on Frequency Response.

No comment.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

No comment.

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

Terra-Gen strongly urges CAISO to refocus its work to alleviate the existing export constraints at the Windhub substation through the proposed 230 kV double circuit transmission line upgrade between Windhub and Vincent. This proposal is only briefly mentioned within the TPP’s Appendix F (Policy Assessment). 

The Draft TPP Fails to Meaningfully Address the Existing Export Constraint at Windhub 

While Terra-Gen understands that CAISO is exploring a new 500 kV line from Windhub to Tesla to address existing congestion on the Path 15 corridor (and potentially increase deliverability at Windhub), the proposed timeline for this project has profound implications for projects seeking to access expiring federal tax credits. CAISO appears to overlook the proposed double circuit upgrade (a policy-driven project) in favor of its economic analysis showing that a new 500 kV line may alleviate generation export constraints in future years in addition to its primary purpose of relieving Path 15 congestion. It may be possible that a new 500 kV line from Windhub to Tesla could unlock deliverability for new resources at Windhub, but CAISO does not adequately assess the timing and cost impacts from accessing deliverability sooner via a more affordable and timely option relative to a potential project with uncertain timing and one where CAISO has acknowledged it has yet to conduct needed engineering analyses to assess broader system impacts. Even if CAISO further fleshes out this new 500 kV line between Windhub and Tesla and decides to move forward with it in a subsequent TPP cycle, it should not delay a faster project in the near-term. 

Unlock New Deliverable Resources Cheaper and Quicker 

As mentioned in our November 2025 comments, the 230 kV double circuit upgrade would create 2,500 MW of deliverability at Windhub and support the immediate development of an additional 1,500 MW of new fully deliverable solar capacity on the proposed gen-ties without requiring additional substation expansion. This comparatively inexpensive project could be achieved on a quicker timeline and deliver meaningful affordability benefits to California ratepayers through the utilization of expiring tax credits. Terra-Gen reiterates that this project can be constructed at a price tag of ~$300M to meet a potential 2030 online date. 

The recent 2025 Transmission Plan Deliverability Allocation Report identified the new Mira Loma-Mesa Constraint that is limiting approximately 16 GW of potentially deliverable energy across southern California. The proposed Vincent-Windhub upgrade offers a potential low cost and near term solution that will provide additional deliverability to a resource rich area unaffected by the Mira Loma-Mesa Constraint while the CPUC is projecting the need to accelerate build rates. While the new constraint and potential solutions are analyzed CAISO should consider all possible solutions to accelerate increasing deliverability on the grid to support California’s goals and develop as many new resources as possible to capture expiring tax credits to the benefit of ratepayers.  

Bypassing the Series Capacitor of the Midway-Whirlwind Line Will Unlock Additional Deliverability 

Terra-Gen supports CAISO bypassing the series capacitor of the Midway – Whirlwind 500 kV line to increase deliverability in the Tehachapi area. As at Windhub, there exists additional commercial interest in developing new resources at the Whirlwind substation which will need to obtain deliverability to solidify project economics. 

3. Please provide your organization’s comments on the Economic Assessment.

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.

Terra-Gen is concerned with CAISO’s decision to reserve deliverability for LDES, particularly at the Whirlwind Substation. The CPUC’s definition of LDES is technology agnostic and allows lithium-ion systems to qualify as LDES provided they meet other definitional requirements (i.e., 8 or more hours of discharge). By contrast, CAISO’s analysis clearly does not follow the same resource alignment as seen with numerous tables within the draft TPP. Table 3-1 (Base and Sensitivity Portfolios by Resource Type and Deliverability Status) shows a classification distinction between LDES and LI Battery – 8 hr. At a bare minimum, CAISO must allow lithium-ion technology to qualify and access this reserved (generic) LDES allocation.  

1. Please provide your organization’s comments on Reliability-driven Projects Recommended for Approval.

2. Please provide your organization’s comments on Policy-driven Projects Recommended for Approval.

3. Please provide your organization’s comments on the Economic Assessment.

Viridon Path 15 LLC (“Viridon”) appreciates the CAISO’s detailed Path 15 corridor economic analyses in the draft 2025-26 Transmission Plan and supports the CAISO’s commitment to identifying holistic Path 15/26 upgrades in the next cycle. The draft plan identifies approximately $1.8 billion in annual Path 15 congestion costs by 2035, reflecting a significant recent upward trend that is projected to continue over the long term.  These high and rising congestion costs highlight the need for solutions that can provide meaningful economic relief to CAISO ratepayers. At the same time, potential Path 15 solutions present complex engineering challenges and unique practical considerations.  To address these issues comprehensively, Viridon supports conducting detailed engineering analysis in the next cycle to determine the specific solution set to address Path 15 congestion.  

As part of the analysis in the 2026-27 Transmission Planning Process, Viridon recommends the CAISO incorporate, in its evaluation of comprehensive Path 15 solutions, upgrades that can be implemented expeditiously to reduce congestion on an accelerated timeline relative to new-build transmission development, and provide immediate economic benefits to California customers.  While the CAISO’s economic analysis shows approximately $1.8 billion in congestion costs in the initial study year, Path 15 congestion already has significant impacts on Northern California customers.[1]  Upgrades that can provide faster relief by leveraging existing facilities and streamlined permitting processes, including reconductoring existing lines, should be valued appropriately and prioritized.  

The draft plan’s approval of the Gates–Los Banos #3 500 kV Line (“LBG3”) series compensation as an economically driven project is consistent with this approach. As the CAISO’s economic studies show, the LBG3 series compensation provides immediate benefits as a standalone upgrade and can be flexibly combined with a broad set of Path 15 solutions to lower congestion and drive additional value, and optimizes existing Path 15 transmission facilities while capitalizing on an expedited permitting path.  Additional upgrades that can be deployed at lower cost and on accelerated timelines can likewise play an important role as part of a broader portfolio of solutions. As the detailed Path 15 engineering studies move forward in the next 2026-27 Transmission Planning Process, Viridon recommends the CAISO continue to evaluate a range of potential solutions that provide maximum economic value while making efficient use of existing transmission assets, including opportunities to deploy such lower-cost, faster-to-implement upgrades alongside longer-term investments.

[1] See the CAISO’s Department of Market Monitoring Fourth Quarter Report on Market Issues and Performance at pages 69-70 (2025-fourth-quarter-report-on-market-issues-and-performance.pdf).

4. Please provide your organization’s comments on Maximum Import Capability Expansion Requests.

5. Please provide your organization’s comments on Frequency Response.

6. Please provide your organization’s additional comments on the Draft 2025-2026 Transmission Plan April 15, 2026 stakeholder call discussion.