Comments on Draft Study Plan

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

In recent comments[1] on the CPUC’s ongoing rulemaking related to Resource Adequacy CAISO indicated that, as part of the 2026-27 TPP it will be conducting a study to help evaluate the ability of storage resources to charge from Energy-Only capacity. CAISO explained that this study will assess the extent to which transmission congestion may limit both generation output and storage charging during non-peak hours, and that the results will inform whether Energy-Only capacity can reasonably be relied upon to meet charging sufficiency requirements across different locations and hours.

ACP-California supports the development of a path to resolve the Energy Sufficiency-Energy Only (“ES-EO”) compliance restrictions preventing the commercialization and development of Energy Only (EO) resources identified for reliability purposes in the Integrated Resource Planning (“IRP”). ACP-California also appreciates CAISO’s commitment to performing an analysis that can help determine the ability of EO resources to support storage charging as part of the 2026-27 TPP. The results of this work that CAISO has committed to perform could provide valuable information to ongoing policy discussions regarding storage charging sufficiency and the potential role of Energy-Only capacity in the slice-of-day RA framework.

Given the significance of this issue – and the novel approach the study may require – ACP-California encourages CAISO to provide additional detail on the scope, methodology, and assumptions associated with this study as the TPP moves forward. In particular, ACP-California recommends that CAISO engage with stakeholders to ensure the study is appropriately scoped to provide the information needed for the CPUC to determine how Energy Only resources might count toward charging sufficiency requirements, which may include partial deliverability for charging in some Local RA areas that CAISO assesses. ACP-California believes it will be important to discuss the study approach with stakeholders, including the CPUC, to ensure the analysis provides the information necessary to inform ongoing RA policy decisions. And it will also be important for the ultimate information provided/solution identified to be implementable with how RA resources are shown on CPUC supply plans.

Finally, ACP-California notes that CAISO has indicated that preliminary results from this study may be available in November 2026. To maximize the usefulness of this work, ACP-California encourages CAISO to ensure that draft results are available in November 2026 and that those results can help inform ongoing proceedings at the CPUC considering storage charging sufficiency and related Resource Adequacy policy issues. Providing draft results on this timeline will ensure the CPUC does not need to wait until the final 2026-27 Transmission Plan is approved in May 2027 to consider whether EO resources may be permitted to support charging sufficiency requirements. This timeline is especially important as developers and LSEs must contract for 6 GW of new NQC resources to come online in 2030-2032 per D. 26-02-057, projects capturing remaining investment tax credits must achieve CODs in 2029-2030, and planned FCDS resources face ongoing network upgrade delays, all of which demand urgency to resolve a potential new role for EO resources in the market.

[1] See CAISO comments on Track 1 Proposal, submitted March 6, 2026, here: https://docs.cpuc.ca.gov/PublishedDocs/Efile/G000/M601/K896/601896043.PDF

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

The Bay Area Municipal Transmission Group (BAMx)^[1] appreciates the opportunity to comment on the California Independent System Operator (CAISO) Draft 2026-2027 Transmission Planning Process (TPP) Unified Planning Assumption and Study Plan (Draft Study Plan). The comments and questions below address the Study Plan posted on February 17, 2026, and discussed during the stakeholder meeting on February 24, 2026. We continue to see CAISO’s desire to work with Stakeholders to enhance each year’s plan. We look forward to working with the CAISO on this collaborative process.

BAMx Supports Choice of a Single Managed Forecast Set for Electricity Planning

BAMx understands that the CAISO’s proposal to continue use of the 2024 (instead of the latest 2025) IEPR planning forecast for the 2026-2027 TPP economic, policy, and bulk system peak studies is driven by the single forecast set agreement between CEC, CAISO, and CPUC (joint Agencies).[2] BAMx supports the CAISO’s approach for the following reasons.

1. Stability is appropriate for long-lead bulk transmission planning

Bulk transmission investments are capital-intensive and long-lived, and therefore particularly sensitive to forecast volatility. The Joint Agencies correctly recognize that the 2025 IEPR cycle introduced material uncertainty related to:

• Known loads,
• Data center growth, and
• The net effects of recent federal policy changes on electrification.

Under these conditions, reliance on the 2024 IEPR Planning Forecast for near-term bulk system studies appropriately prioritizes planning stability and analytical consistency while those uncertainties are evaluated and refined.

2. The proposal does not ignore emerging load risks

Critically, the Joint Agencies’ proposal does not disregard emerging load growth or reliability concerns. Instead, it targets newer, more aggressive assumptions to the planning processes where they are most relevant, including:

• Local transmission planning,
• Distribution planning, and
• Local area reliability studies.

By applying the 2025 IEPR local reliability forecast with known loads to local studies, the agencies ensure that near-term, location-specific risks are addressed, even as bulk system studies maintain a stable baseline.

3. Managing uncertainty is preferable to embedding it in long-term infrastructure decisions

While newer forecasts incorporate additional load categories, uncertainty alone is not a sufficient basis for committing ratepayers to long-lived infrastructure. In the face of unresolved interactions among known loads, data centers, and policy-driven demand modifiers, the Joint Agencies’ decision to avoid prematurely embedding these assumptions into bulk transmission planning is reasonable and consistent with sound planning practice.

In summary, BAMx emphasizes that this support is conditional on the Joint Agencies’ commitment to continued monitoring, transparency, and adjustment should observed load growth or resource development materially diverge from the 2024 IEPR Planning Forecast.

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

[2] CAISO Stakeholder Meeting Presentation, dated February 24, 2026, p.27.

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

Need to Account for Significant Changes in Resource Mix and Location in 2026-2027 TPP While Considering Approval of Policy-Driven Projects in 2025-2026 TPP

BAMx noticed that the resource mix and their locations identified in several study areas in 2026-2027 TPP study plan differ significantly from those assumed in the 2025-2026 TPP. For example, as shown in Table 1, the assumed geothermal resources have increased significantly from 1,639MW in the 2025-2026 TPP to 5,105 MW in the 2026-2027 TPP. However, upon closer inspection, the geothermal resources assumed in the SCE Metro and SCE Eastern study areas in the 2025-2026 TPP have all but disappeared in the proposed 2026-2027 TPP Base portfolio.

Table 1:  A Comparison of Assumed Geothermal Resources in Base Portfolio: 2026-2027 TPP vs. 2025-2026 TPP

In addition to the geothermal resources, the 2025-2026 TPP Base portfolio assumed 1,750MW of out-of-state (OOS) wind resources in 2035. However, we see 0MW of OOS wind in SCE Metro in the proposed 2026-2027 TPP Base portfolio.[1]  Therefore, any delivery network upgrades triggered by those geothermal and OOS wind resources in the SCE Metro (and SCE Eastern study) areas would require closer scrutiny before their approval in the 2025-2026 Transmission Plan.

BAMx also notes that the 1,607MW of Humboldt (North of Greater Bay) area Offshore Wind assumed in the 2025-2026 TPP in the year 2035 is now delayed to 2041 per the proposed 2026-2027 TPP Base portfolio. Therefore, BAMx believes that the previously approved offshore wind-driven transmission projects should be re-evaluated for continued need, timing, and scope in light of materially changed resource assumptions.

In summary, BAMx suggests that any delivery network upgrades triggered by a resource mix that is exposed to considerable volatility based on the 2026-2027 TPP base portfolio would require closer scrutiny before their approval in the 2025-2026 Transmission Plan, especially if those resources driving the network upgrades are generic, i.e., not part of the baseline resources.

The CAISO Needs to Address Apparent Discrepancy with Storage Resource Capacity Recommended by CPUC PSP

The California Public Utilities Commission’s (CPUC) recently adopted Preferred System Plan (PSP) includes 25,458MW of new storage resources by 2036 (2041) timeframe as summarized in Table 2 below.^[2] However, as shown in Table 2, the CAISO’s February 24^th presentation shows the storage capacity at 27,286MW. Moreover, the breakdown of 4-hour, 8-hour, and long-duration energy storage (LDES) assumed in the CAISO presentation departs from the CPUC PSP assumptions.

Table 2: A Comparison of Assumed Storage Resources in Base Portfolio: CAISO vs. CPUC PSP

BAMx requests that CAISO either (1) align the Final Study Plan resource mix with the CPUC PSP assumptions, or (2) clearly document and justify any deviations, including the implications for deliverability and transmission needs.

BAMx

BAMx appreciates the CAISO staff’s efforts in incorporating non-CPUC jurisdictional integrated resource plans (IRP) in the analysis with the CPUC busbar mapped IRP base portfolio.[3]  In cases where no CPUC portfolio is mapped to the same or nearby locations, CAISO will model the POU resource at the location identified by POU and reduce the CPUC resource at the location that is behind the same constraint in consultation with CPUC.[4] BAMx finds this approach to be reasonable, and consistent with the approach implemented in the 2025-2026 TPP.

It appears that the non-CPUC-jurisdictional entities’ IRPs have cumulatively assumed retirement of gas capacity of 108 MW beginning in 2026 to 434 MW by 2037.[5] In the CPUC 2026-2027 TPP Base portfolio, the CPUC assumes 1,653MW of new gas capacity that was not retained.[6] BAMx requests clarification on how the CAISO plans to reconcile CPUC portfolio assumptions with non-CPUC-jurisdictional entities’ gas capacity that is not retained.

BAMx Requests More Clarity on How Resource Portfolio Adjustments will be Made to Model Unaccounted for TPD, Additional In-Development Resources, and Non-CPUC Jurisdictional Resources

BAMx appreciates the CAISO explanation during the February 24^th stakeholder meeting regarding how the unaccounted for TPD amounts are calculated at each bus/location.[7]  The challenge is that the queue of interconnection requests and the allocated TPD can change more quickly or differ from the specific resources modeled in the CPUC's Integrated Resource Plan (IRP).

BAMx also understands that the CAISO intends to map 4-hour battery storage as proxies for unaccounted for TPD at specific locations. In addition to these proxies for the unaccounted for TPD, the CAISO will make adjustments to the portfolio to account for additional in-development resources that might be missing from CPUC IRP portfolios, as well as non-CPUC Jurisdictional IRP resources. BAMx requests that the CAISO make the details of all these adjustments available to the stakeholders with adequate granularity. The stakeholder vetting would help minimize the possibility of triggering unnecessary delivery network upgrades driven by excessive resources behind certain deliverability constraints.  Greater transparency would help ensure that delivery network upgrades are driven by realistic, location-specific needs rather than conservative proxy assumptions in the 2026-2027 TPP.

[1] However, as much as 3,000MW of OOS wind is assumed in study year 2014 in the SCE Metro area.

[2] Proposed Decision Requiring 2029-2032 Electric Resource Procurement And Transmitting Portfolios For 2026-2027 Transmission Planning Process, R.25-06-019 (Feb. 26, 2026) at 56: https://docs.cpuc.ca.gov/PublishedDocs/Published/G000/M600/K854/600854771.pdf.

[3] CAISO Stakeholder Meeting Presentation, dated February 24, 2025, pp.69-71.

[4] Ibid, p. 71.

[5] Ibid, p. 71.

[6] Ibid, p. 65.

[7] Ibid, p. 72.

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

No comments at this time.

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

BAMx appreciates the CAISO explanation of the frequency-response assessment and the study scenarios included in the draft study plan. Scenario 3[1] states that frequency response will be determined with “as minimal a Battery Energy Storage Systems (BESS) headroom as possible for the given case, up to a limit of 10%.” Because this assessment will use spring off-peak conditions, many BESS units are likely to be operating in charging mode. It is unclear whether the 10% headroom limit is intended to apply to BESS units that are charging, or only to those that are discharging, or both.

In addition, BESS units in charging mode may already be at or near their maximum charging limits, making a 10% headroom requirement infeasible. If a 10% headroom cannot be achieved under these conditions, it is unclear whether CAISO intends to proceed with a lower headroom or adjust the case assumptions to force the 10% threshold.

BAMx recommends that the final study plan clarify (1) whether the 10% headroom limit applies to BESS units in charging mode, and (2) how CAISO will treat cases where 10% headroom is not achievable under spring off-peak conditions. This clarification will help stakeholders understand the assumptions underlying the frequency-response assessment and ensure consistent interpretation across study scenarios.

[1] CAISO Stakeholder Meeting Presentation, dated February 24, 2025, pp.95.

5. Please provide your organization's Economic Study Requests

 No comments at this time.

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

 No comments at this time.

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

Electromagnetic Transient (EMT) Studies

BAMx encourages CAISO to continue the development of system-wide EMT models and incorporate these studies into the TPP. A comprehensive system-wide EMT model may provide a more accurate assessment of Inverter-Based Resources (IBRs) plant controls in the sub-transient time domain when evaluating primary and fast frequency response capabilities from IBRs. Developing these models may help identify any deficiencies not currently captured by traditional transient stability study methods when assessing frequency response.

BAMx Appreciates Commenting Opportunity

BAMx appreciates the opportunity to comment on the draft Study Plan. Overall, BAMx supports the CAISO’s proposed planning framework and offers the above comments to improve transparency, alignment, and confidence in the resulting transmission solutions. We plan to work with CAISO staff to continue improving the Study Plan.

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

Please see CalCCA comments in Section 7.

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

Please see CalCCA comments in Section 7.

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

Please see CalCCA comments in Section 7.

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

Please see CalCCA comments in Section 7.

5. Please provide your organization's Economic Study Requests

Please see CalCCA comments in Section 7.

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

Please see CalCCA comments in Section 7.

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

The California Community Choice Association (CalCCA) appreciates the opportunity to comment on the California Independent System Operator’s (CAISO) 2026-2027 Transmission Planning Process (TPP) Draft Study Plan. The comments herein focus on the ability of load-serving entities (LSE) to obtain deliverability for in-state and out-of-state resources through the TPP, MIC, and deliverability reservation processes. CalCCA recommends that the CAISO:

• Enhance its decision-making processes for the TPP to account for uncertainty and ensure a competitive market;
• Expeditiously initiate a stakeholder process within the Resource Adequacy Modeling and Program Design initiative to review the MIC expansion request process and other elements of the MIC process to identify enhancements necessary to support the development of out-of-state resources;
• Document within the study plan the process for releasing reserved deliverability considering the Local Regulatory Authority (LRA) planning assumptions and actual investments in new capacity and development milestones of contracted resources; and
• Report annually on how much and when deliverability reserved for long-lead time (LLT) resources is released going forward for transparency.

TPP Decision Making Under Uncertainty

The CAISO, in coordination with the California Public Utilities Commission (CPUC), should reform its transmission planning tools and decision-making process to be more robust under uncertain scenarios. The ability for new capacity to interconnect to the transmission system is a key constraint on decarbonization efforts and on a competitive market for capacity. System planning is becoming increasingly challenged by uncertain assumptions, given the emergence of new large loads like data centers, changes in federal policy, and new technology innovation. The 2026-2027 TPP should focus on specifically identifying risks and uncertainty bounds for a robust optimization[1] to inform transmission planning decision-making and increasing the burden of proof on model assumptions that defer in-state transmission investments. Doing so will establish an expectation that the Transmission Plan is both cost-effective and low risk.

Research sponsored by Sonoma Clean Power and Peninsula Clean Energy has demonstrated the application of robust optimization.[2] Results show that more proactive approval of transmission capacity, particularly lines that enable a diverse set of resources that satisfy grid needs under a range of scenarios, are the primary opportunity to improve robustness of California’s grid planning. The CAISO should therefore reform transmission planning tools and decision-making processes to account for uncertainty using robust optimization methods that result in a portfolio that is successful across a range of scenarios.

MIC Expansion Requests

CalCCA appreciates the CAISO conducting the MIC expansion process to facilitate the contracting of imports necessary to support long-term policy needs. However, for the reasons described in CalCCA’s December 5, 2025, comments, the MIC expansion process, and other elements of the MIC process, may be insufficient to provide the certainty necessary for long-term procurement activities to support the number of imports projected in the CPUC portfolios.[3]

The process for expanding MIC through upgrades should account for both the local regulatory authorities’ (LRA) planning assumptions and actual investments and development milestones of contracted out-of-state resources. Consistent with the Joint Parties’ catalog request, CalCCA encourages the CAISO to expeditiously initiate a stakeholder process within the Resource Adequacy Modeling and Program Design initiative to review the MIC expansion request process and other elements of the MIC process to identify enhancements necessary to support the development of out-of-state (OOS) resources.[4]

Deliverability Reservations

Like in past TPPs, the CPUC has identified quantities of LLT resources for which the CAISO is to reserve deliverability: OOS wind, in-state geothermal, offshore wind and location-constrained Long Duration Energy Storage (LDES).[5] CalCCA agrees that a reservation process is necessary to allocate deliverability to LLT resources that have longer project development cycles, and which may not be compatible with the updated TPD allocation process established in the Interconnection Process Enhancements initiative. 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 to meet policy and reliability objectives. Because the CPUC’s 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 therefore document within the study plan the process for releasing reserved deliverability considering the LRAs’ planning assumptions and actual investments in new capacity and development milestones of contracted resources. The CAISO should also report on how much and when reserved TPD is released going forward for transparency. This process should take place annually within the TPP, beginning with the 2026-2027 TPP Draft Study Plan, to ensure reservations continue to reflect actual resource procurement and development.

[1]            Robust optimization finds a solution that is successful across a range of scenarios, with a focus on minimizing tail risk.

[2]            Joint Comments of Sonoma Clean Power Authority and Peninsula Clean Energy Authority on the Order Instituting Rulemaking, R.25-06-019 (Aug. 1, 2025), at 3-7 and Appendix A: https://docs.cpuc.ca.gov/PublishedDocs/Efile/G000/M574/K980/574980356.PDF.

[3]            See CalCCA, Comments on Policy & Economic Preliminary Assessment Study Updates, 2025-2026 TPP (Dec. 5, 2025):  https://stakeholdercenter.caiso.com/Comments/AllComments/8dedac49-35a3-4164-96aa-f620710b1a18#org-78bbd38a-c496-43a8-9140-b07f4ff11739.

[4]            The Joint Parties Catalog Request (March 2, 2026): https://stakeholdercenter.caiso.com/Comments/AllComments/04c6df24-b13b-4e59-b83b-7dd99085b4ef#org-85e61823-658d-40e8-9bfe-16753fbfe6cb.

[5]            Decision Requiring 2029-2032 Electric Resource Procurement and Transmitting Portfolios for 2026-2027 Transmission Planning Process, R.25-06-019 (Feb. 26, 2026) at 72: https://docs.cpuc.ca.gov/PublishedDocs/Published/G000/M600/K398/600398976.PDF.

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

The Public Advocates Office at the California Public Utilities Commission (Cal Advocates) provides these comments on the California Independent System Operator’s (CAISO) stakeholder meeting on the 2026-2027 Transmission Planning Process–Draft Study Plan on February 24, 2026.  Cal Advocates is an independent ratepayer advocate with a mandate to obtain the lowest possible rates for utility services, consistent with reliable and safe service levels and the state’s environmental goals.[1]

Cal Advocates has no comments on the Draft Study Plan Reliability Assessment.

[1] Cal. Pub. Util. Code, § 309.5.

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

Cal Advocates has no comments on the Draft Study Plan Policy Assessment.

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

Cal Advocates has no comments on the Draft Study Plan Economic Assessment.

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

CAISO should evaluate the impact of new large loads[1] on the bulk system in its 2026 Frequency Response Assessment.  In 2025 the North American Electric Reliability Corporation (NERC) identified potential risks associated with new large load operations.[2]  According to NERC, these new large loads such as data centers can have rapid and unexpected fluctuations in demand.[3]^,[4] Further, “major swings in load, can impact the ability to maintain frequency, regulate transmission voltage and otherwise maintain stability” on the bulk system.[5]  In January 2026, NERC also reported that there are gaps in existing practices and requirements and reliability standards for new large loads.[6]  In March 2026, NERC will release a white paper on the gaps in existing practices, requirements, and reliability standards for new large loads and provide recommendations to address these gaps.[7]  NERC’s March 2026 large load reliability recommendations should be addressed in CAISO’s 2026-2027 Transmission Planning Process (TPP) to maintain bulk system reliability.  Specifically, CAISO should collaborate with stakeholders to address the gaps in their existing practices that do not account for the risks associated with large load interconnections.[8]  CAISO and its participating transmission owners should also update their interconnection requirements and study processes to address the gaps identified in the NERC Large Load White Papers to account for the potential risks of large load interconnections.[9]

[1] Industry Recommendation Large Load Interconnection, Study, Commissioning and Operations, NERC September 9, 2025 at p. 1. Large Load Definition: “Any commercial or industrial individual load facility or aggregation of load facilities at a single site behind one or more point(s) of interconnection that can pose reliability risks to the BPS due to its demand, operational characteristics, or other factors. Examples include, but are not limited to, data centers, cryptocurrency mining facilities, hydrogen electrolyzers, manufacturing facilities, and arc furnaces.”

[2] Industry Recommendation Large Load Interconnection, Study, Commissioning and Operations, NERC September 9, 2025 at p. 1.

[3] Characterization and Risks of Emerging Large Loads, NERC, July 2025 a p. 15. “Many large loads—especially data centers and other computational loads—may shift their computational demand to a different physical facility. These shifts may occur in response to changes in factors such as energy pricing, emission intensity, and currency pricing. However, without knowing the exact causes for these shifts and when they will occur, system operators cannot account for the load response or create accurate forecasts, potentially leading them to use more balancing reserves than expected to handle large load power swings.”

[4] Assessment of Gaps in Existing Practices, Requirements, and Reliability Standards for Emerging Large Loads (Draft), NERC Large Loads Working Group White Paper, March 2026, pp. 14, 40, 44 and 45.

[5]  Industry Recommendation Large Load Interconnection, Study, Commissioning and Operations, NERC September 9, 2025 at p. 1.

[6] Large Load Frequently Asked Questions, NERC, January 2026, p. 1.

[7] Large Load Frequently Asked Questions, NERC, January 2026, p. 1.

[8] Assessment of Gaps in Existing Practices, Requirements, and Reliability Standards for Emerging Large Loads (Draft), NERC, March 2026, p. 54.  Recommendation 4.

[9] Assessment of Gaps in Existing Practices, Requirements, and Reliability Standards for Emerging Large Loads (Draft), NERC, March 2026, p. 54.  Recommendation 5.

5. Please provide your organization's Economic Study Requests

Cal Advocates has no comments on the Economic Study Requests.

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

Cal Advocates has no comments on the Maximum Import Capability expansion requests.

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

CAISO and its Participating Transmission Owners should provide cost estimates for the portion of new transmission projects that are associated with integrating new data center load.

For the 2026-2027 Transmission Planning Process (TPP), CAISO and its participating transmission owners (PTOs) should provide cost estimates for the portion of new transmission projects that are associated with integrating new data center load.  Currently, CAISO and its 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 load and new building and transportation electrification loads are undistinguishable from other load impacts.  California is in the midst of determining how to respond to new data center load and how to allocate the costs for accommodating new data center load.  For transparency, CAISO and its PTOs should identify the data center-driven transmission costs in the 2026-2027 TPP.  This will enable California to properly evaluate the impact of integrating new Artificial Intelligence (AI) and other data center load.  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.[1]^,[2],[3]  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.[4]

Cal Advocates also recommends that the CAISO 2026-2027 TPP identify any new transmission investments that would be unnecessary if not for new data center load. 

[1] The data center balance: How US states can navigate the opportunities and challengees, McKinsey & Company,  August 8, 2025, https://www.mckinsey.com/industries/public-sector/our-insights/the-data-center-balance-how-us-states-can-navigate-the-opportunities-and-challenges

[2] This utility exec is powering the data center boom, Politico, November 14, 2025 at p. 1. https://www.politico.com/newsletters/california-climate/2025/11/14/this-utility-exec-is-ready-for-the-data-center-boom-00653285

[3] AI, Data Centers, and the U.S. Electric Grid: A Watershed Moment, Belfer Center for Science and International Affairs, February 10, 2026. https://www.belfercenter.org/research-analysis/ai-data-centers-us-electric-grid

[4] White House to host Big Tech after pledge to rein in power costs, Reuters, February 25, 2026. “The White House said on Wednesday [February 25, 2026] it will host leading data center and artificial intelligence companies next week, with attendees expected to include Microsoft (MSFT.O), opens new tab, Amazon (AMZN.O), opens new tab, Anthropic and Meta Platforms (META.O), opens new tab to formalize a deal to shield consumers from rising power costs.”

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

Please find attached comments.  Copy was submitted to the "confidential filing" portal by email when this account did not activate.  Activation of account a few minutes ago (aftrer comment deadline) allows this submittal now.  

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

Clearway respectfully requests that CAISO evaluate the addition of a third 230/500 kV transformer bank at Red Bluff to mitigate growing congestion on the existing transformer banks. The generation at Red Bluff 230 kV is connected to the grid radially via two 230/500 kV transformer banks, each with a normal rating of 1,120 MW, which together limit maximum output for generation interconnected at the station.

The busbar mapping for CPUC’s base case resource portfolio for the 2026-27 TPP shows 2.6 GW mapped at Red Bluff 230kV behind the 230/500 kV transformer constraint, including 500 MW of generic resources. These resources, if built, would face material and increasing curtailment risk due to the existing transformer bottleneck.

The curtailment risk and congestion-related costs at Red Bluff are already visible today. Over the past four years, congestion rents associated with the Red Bluff transformer constraint have totaled approximately $38 million in system costs (shadow price × rating). This magnitude of congestion indicates:

• A persistent economic inefficiency,
• A clear signal of grid need,
• A strong likelihood that a cost-effective network upgrade would yield systemwide benefits, and
• That congestion observed under current levels of online capacity will only worsen as new additions come online.

Commercial interest demonstrated by the interconnection queue shows strong developer interest, robust solar resource quality, and a continued likelihood of renewable build-out in the area. Today, the interconnection queue includes 367 MW of solar PV capacity pre-Cluster 15 and 535 MW in Cluster 15, in addition to 2,070 MW of PV capacity already online. These high-value resources should not remain stranded if a scalable, economically justified solution is available.

Operationally, this challenge is likely to intensify. As transformer loadings approach thermal limits, real-time operational ratings are often derated significantly, reducing effective transfer capability further. This derating becomes especially pronounced during an outage of one transformer bank, a condition observed with some regularity. Under such circumstances, flows must be restricted to the rating of a single transformer, substantially amplifying curtailment risk and congestion costs. There is additional concern that, as more solar generation is added behind the existing two banks, these operational derates will become increasingly common even under normal conditions, without any outages, due to flows more often approaching and exceeding the transformer limits once the new generation comes online.

For these reasons, Clearway encourages CAISO to perform an economic evaluation of adding a third transformer bank at Red Bluff and assess whether this upgrade would cost-effectively:

• Reduce congestion rents,
• Improve renewable injection,
• Enhance operational flexibility and resiliency during outages or derates (syncing transmission planning with observations in operations), and
• Support continued clean-energy growth in a high-quality solar region.

Clearway appreciates CAISO’s consideration and looks forward to engaging further in the economic assessment process.

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

South-to-North Congestion on Paths 26 and 15 Poses a Growing and Underexamined Risk to Northern California Reliability That Should Be Explicitly Addressed in the Reliability Studies 

While Fervo has no specific comments on the reliability assessment methodology as presented, the reliability studies should account for the compounding pressure that south-to-north transmission constraints will place on the Northern California system as the portfolio evolves. 

As thermal generation retires and variable renewable resources grow, Northern California faces increasing resource adequacy pressure — particularly during evening peak hours when solar output declines. When local resources and northern imports are insufficient to serve load, the system will draw more heavily on south-to-north flows across Paths 26 and 15. Those paths are already congested. Greater reliance on those paths concentrates reliability risk precisely where the system is most vulnerable. 

Fervo encourages CAISO, in coordination with the CPUC, to assess this dynamic explicitly in the reliability studies and to carry those findings directly into the evaluation of whether Path 26 and 15 upgrades are warranted. 

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

1.  The Final Study Plan Should Reflect the CPUC Final Decision's Expanded Deliverability Reservation Scope for All Geothermal Resources 

The Draft Study Plan reflects the recommendation from the CPUC's Proposed Decision reserving deliverability for "in-state geothermal resources selected in the base case." However, the CPUC expanded this instruction in the Final Decision to cover all geothermal resources in the portfolio, including both in-state and imported resources. Fervo requests that CAISO confirm the Final Study Plan incorporates the Final Decision recommendation to apply deliverability reservations across the full geothermal portfolio. 

2. The Draft Study Plan Omits Detail on Geothermal and EGS Transmission Needs and Should be Resolved for the Final Study Plan  

The Draft Study Plan includes detailed discussion of regional coordination for out-of-state wind, with dedicated modeling of Wyoming, Idaho, and New Mexico wind resources and explicit attention to interregional transmission planning for those corridors. Geothermal and EGS resources would benefit from comparable study. The CPUC emphasized the need for clean-firm resources by 2032 in the latest IRP procurement order and geothermal was selected for 5,104 MW of fully deliverable capacity in the 2036 base portfolio and up to 8,309 MW in the 2041 sensitivity portfolio. CAISO should provide a more robust study of the transmission capacity needed to support the timely development and delivery of these critical reliability resources. 

Fervo encourages CAISO to include in the Final Study Plan a dedicated discussion of the transmission infrastructure needed to deliver geothermal and EGS to California load, covering key delivery corridors, binding constraints, and regional coordination requirements for resources sited outside the CAISO footprint. 

3. South-to-North Congestion on Paths 26 and 15 is a Structural Barrier to Delivering Commercially Viable EGS from Utah to California, and Deferring Upgrades Creates Compounding Risks the TPP Must Directly Confront 

The Draft Study Plan acknowledges that RESOLVE modeling identified approximately $1 billion in Path 26 and Path 15 upgrades as beneficial across both the base and sensitivity portfolios. It further notes that CPUC staff subsequently remapped resources from SDG&E into SCE and PG&E to reduce reliance on those constrained south-to-north paths and concludes that "the full TPP study process will be needed to determine if Path upgrades are necessary." 

Fervo supports CAISO's continued evaluation of these upgrades, and urges CAISO to approach that evaluation with clear-eyed recognition of the implications of this remapping: 

• South-to-north congestion directly constrained the CPUC's ability to site EGS at commercially viable Utah locations. The most commercially active EGS development is currently taking place in Western Utah. Developers in Utah, including Fervo, are in the best position to bring projects online to meet the CPUC’s procurement timeline, utilizing a deliverability pathway via Paths 26 and 15. The CPUC’s portfolio maps EGS resources instead to Northern California, which avoids transmission limitations on Paths 26 and 15, but does not reflect commercial reality. To avoid necessary transmission upgrades, the portfolio overstates the resource potential in Oregon and Northern California, ignores where EGS is being built, and precludes the most realistic and affordable options for meet reliability needs. 

• Failing to upgrade Paths 26 and 15 forecloses California's access to a highly viable source of clean firm capacity. EGS in Utah is commercially available today at utility scale and can be delivered to California LSEs on the necessary timeline and at cost-effective prices – if sufficient transmission capacity is made available. The CPUC’s busbar mapping portfolio defers the transmission investments that would support these commercially viable Utah resources by instead selecting theoretical resources that (because they are not under development at scale, speed or cost) are not able to meet California’s procurement and reliability needs. This planning choice has important ramifications: deferring Path 26 and 15 upgrades will delay or prevent the delivery of real EGS resources identified by the CPUC as essential to meeting reliability and SB100 goals. 

Fervo urges CAISO to designate the Path 26/15 upgrade analysis as a high-priority work stream in the 2026-2027 TPP, to engage directly with the CPUC on the transmission implications for critical imports, and to evaluate Path upgrade scenarios that would enable greater EGS deployment at commercially active locations. 

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

The Production Cost Simulation Should Explicitly Quantify the Cost of South-to-North Congestion on Paths 26 and 15 to Support a Complete Evaluation of Whether Path Upgrades Are Warranted 

Fervo has no specific Economic Assessment input to submit at this time. However, understanding the congestion and curtailment costs associated with Paths 26 and 15 constraints — and the production cost benefits of relieving them — is essential to a full and fair evaluation of whether Path upgrades are justified as economic or policy-driven transmission investments. Fervo encourages CAISO to ensure the production cost simulation captures these costs with sufficient granularity to inform that determination. 

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

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”), including Southern California Edison (“SCE”), Ava Community Energy, Clean Power Alliance (“CPA”), Desert Community Energy, and Shell Energy, 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. We offer the following summary of our comments for consideration: 

The 2026-2027 TPP Must Close the Gap Between California's Firm Clean Energy Needs and the Transmission Planning Required to Deliver Commercially Viable EGS Resources 

The 2026-2027 TPP takes place at a pivotal moment for EGS development and California’s future grid reliability. EGS is commercially proven, procured in significant quantity by California LSEs, and identified by the CPUC as a critical clean firm resource in meeting California's affordability, reliability and decarbonization goals. Transmission planning to support the delivery of EGS is urgently needed to ensure that the most timely and economic resources are available to the CAISO system. 

The Draft Study Plan lacks a detailed evaluation of geothermal transmission needs. To help close this gap in planning, Fervo respectfully requests that CAISO take the following steps in the Final Study Plan and throughout the 2026-2027 TPP: 

1. Confirm that the Final Study Plan reflects the CPUC Final Decision's instruction to reserve deliverability for all geothermal resources. 

2. Include dedicated treatment of geothermal and EGS transmission planning needs, commensurate with the treatment given to other out-of-state resources. 

3. Prioritize the Path 26/15 upgrade analysis with full consideration of the compounding risks that south-to-north congestion poses for Northern California reliability, EGS deliverability, and California's ability to access the most commercially viable clean firm generation. 

Fervo looks forward to continued engagement with CAISO and stakeholders throughout this planning cycle. 

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

No comments.

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

No comments.

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

No comments.

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

No comments.

5. Please provide your organization's Economic Study Requests

Kern-Southland Energy Link, LLC appreciates the opportunity to provide comments on the 2026-2027 Transmission Planning Process (TPP) update provided on February 24, 2026.

Kern-Southland Energy Link LLC is pleased to submit the Kern-Southland Energy Link (K-SEL) project to CAISO for consideration as an economic study request in the 2026-2027 Transmission Planning Process. K-SEL is a bi-directional multi-value project with reliability, policy, and economic benefits, and enables the deliverability of cheaper FCDS resources deep into the LA Basin. K-SEL would provide a new import/export path from Kern County to deep into the LA Basin in the form of a controllable DC tie that could be optimized to alleviate congestion on Path 26, which experienced nearly 4,700 hours of congestion and a total cost of congestion of ~$350MM in the CAISO 25-26 2035 base portfolio preliminary production cost model (PCM) results. We respectfully request CAISO to study K-SEL for its ability to reduce LCR and reliance on Aliso Canyon storage by providing deliverability of 2 GW of cheaper resources into the LA Basin without major upgrades to the intra-basin transmission system, the ability to provide voltage support to the coastal?LA Basin system, and economic congestion management benefits from having a controllable North South backbone DC transmission link..

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

No comments.

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

No comments.

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

GridLiance West respectfully requests that the CAISO conduct economic studies in the 2026 – 2027 Transmission Planning Process on the following 2 projects (see attached):

• High West Transmission Project
• Sloan Canyon- Mead Project 

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

Horizon West Transmission (HWT) respectfully requests that the CAISO conduct economic studies in the 2026 – 2027 Transmission Planning Process for the following two projects (see attached): 

• Cielo Azul – Dunes – Imperial Valley Project
• A joint HWT and Imperial Irrigation District (IID) submission for the Dunes – Slab City – Devers 500kV Project

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

The Metropolitan Water District of Southern California appreciates the opportunity to comment on the 2026-27 draft study plan.  With responsibility for delivering water supply to more than 19 million people located in southern California, MWD owns a 230 kV transmission system (the Colorado River Aqueduct Transmission System, or CRATS) built and operated solely for delivering electric power to the five pumping stations along the Colorado River Aqueduct. MWD is very concerned over the growing reliability risk continuously shown in past cycles of CAISO TPP studies. Please refer to MWD’s stakeholder comments on the preliminary 2025-26 study results submitted on October 9, 2025. MWD would like to see this current study plan include actual steps to address our concerns, by [1] illustrating that the existing RAS cited in past studies can fully mitigate the NERC reliability violations in our system and by [2] evaluating additional capital projects, such as Pattern Energy’s Main West Desert Transmission proposal, for complete mitigation of such reliability standard violations.

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

MWD is primarily concerned with mitigating potential operational and reliability impacts of on the CRATS and downstream impacts to CRA water operations.  However, MWD would encourage studying capital project mitigations, such as Pattern Energy’s Main West Desert Transmission, for any policy or economic benefits.

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

MWD is primarily concerned with mitigating potential operational and reliability impacts of on the CRATS and downstream impacts to CRA water operations.  However, MWD would encourage studying capital project mitigations, such as Pattern Energy’s Main West Desert Transmission, for any policy or economic benefits.

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

MWD has no comments on this topic at this time

5. Please provide your organization's Economic Study Requests

MWD has no comments on this topic at this time

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

MWD has no comments on this topic at this time

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

MWD has no comments on this topic at this time

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

No comments at this time.

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

NCPA appreciates the opportunity to provide comments on the February 24 stakeholder meeting on the 2026-2027 draft study plan.

NCPA echoes CPUC staff’s recommendation (at page 80 of the Draft Study Plan) that CAISO defer approval of transmission lines needed to deliver OOS wind until more analysis is done, especially given CAISO’s estimated $20 billion price tag for the transmission needed to deliver OOS wind. NCPA urges CAISO to conduct this additional analysis with the goal of finding the most cost-effective transmission solution.

NCPA notes that the CPUC transmitted a low wind sensitivity portfolio as compared to previous years due to potential impacts on wind resources “for reasons generally outside of California’s control” (at page 73 of the Draft Study Plan). NCPA urges CAISO to ensure that transmission solutions selected in prior TPPs for delivery of wind resources have not also been affected by factors outside of California’s control which would make them unnecessary or less cost-effective solutions. If the projects are no longer needed, CAISO should cancel the projects sooner rather than later to decrease the cost impacts of canceled projects on ratepayers.

NCPA would like to encourage CAISO to evaluate all transmission solutions through the lens of affordability. CAISO should focus on expanding the regional markets and evaluating the resource sharing gains from a larger footprint as part of its evaluation.

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

 No comments at this time.

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

 No comments at this time.

5. Please provide your organization's Economic Study Requests

 No comments at this time.

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

 No comments at this time.

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

 No comments at this time.

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

Ormat is one of the largest developers and suppliers of geothermal power in California and Nevada. As a developer, owner, and operator of geothermal energy facilities in California and Nevada, Ormat and its affiliates are committed to well-structured markets and processes that encourage the development and procurement of high-quality generation resources and promote the best value for ratepayers. Prudent transmission investment through the CAISO’s Transmission Planning Process (“TPP”) is extremely important for geothermal development, because unlike other resource types, geothermal resources must be developed near geothermal reservoirs/fields. This requires transmission be planned and built to support Known Geothermal Resource Areas (“KGRAs”).

Ormat appreciates the CAISO’s detailed study plan. In these comments, Ormat:

• Recommends CAISO study options to add a CAISO intertie at the Hilltop 345 kV substation to allow load-serving entities to cost-effectively access out-of-state geothermal capacity, and
• Recommends CAISO give stakeholders the opportunity to comment on the study inputs and assumptions after CAISO has initially translated the CPUC’s capacity/substation mappings.

Geothermal market activities are currently focused mostly on developing assets outside of California to serve consumers inside California. Recognizing this reality, CPUC staff mapped over 750 MW of capacity related to the Hilltop 345 kV substation in Northeastern California. Related transmission investment in the area would facilitate development of in-state geothermal resources in the Surprise Valley Known Geothermal Resource Area (“KGRA”) and imported resources from Northern Nevada. It would also have synergies with wind development opportunities in the region.

Ormat is very concerned that wheeling geothermal energy to Malin may not be as economically viable as alternative locations, because it may currently involve expensive wheels through BPA and PacifiCorp. The CPUC asked CAISO to study transmission solutions to increase import capacity between Hilltop and Malin, to facilitate delivery of geothermal across the CAISO system.[1] Ormat remains concerned and recommends the CAISO additionally study other options to add a CAISO intertie at Hilltop.

Finally, Ormat recommends CAISO give stakeholders the opportunity to comment on the study inputs and assumptions after CAISO has initially translated the CPUC’s capacity/substation mappings.  In the past, CAISO has altered the mapped capacity and Ormat believes stakeholders should be given the opportunity to provide additional context if major capacity additions/subtractions have been made from the final portfolio approved by the CPUC. Major deviations in this part of the process could have unintended consequences on the accuracy of the study and resulting transmission development costs.

[1] Decision 26-02-057, issued March 5, 2026, pg. 98.

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

Pacific Gas and Electric Company (PG&E) appreciates the opportunity to comment on the California Independent System Operator (CAISO) Draft 2026-2027 Transmission Planning Process (TPP) Unified Planning Assumption and Study Plan (Draft Study Plan).

PG&E understands the CAISO must study the TPP portfolio as provided by the California Public Utilities Commission (CPUC).  At the same time, PG&E urges the CAISO to also consider the feasibility of the resource mapping in the 2026-2027 TPP portfolio and other scenarios when approving new transmission.  

In-state development of resources, to-date, has largely favored resources in Southern California, as well as out-of-state resources delivering into Southern California.  Given the degree of uncertainty surrounding new resource development in Northern California (including geothermal) due to longer development timelines and costs, PG&E is concerned that load serving entities will continue to primarily procure resources located south of Path 26 and out-of-state.  Stated differently, the new resources (including generic and geothermal) busbar mapped to Northern California may not materialize as resource development has primarily been focused in Southern California to-date. This has implications for reliability and could necessitate either transmission upgrades to Path 26 and Path 15 or alternative transmission solutions to ensure energy can be delivered to PG&E load centers.  In fact, the CPUC itself noted in its reliability modeling for the decision on the 2026-2027 TPP and procurement order, “[a]s staff iterated with increasing amounts of PCAP added to tune 2032 to 0.1 LOLE, the share of PCAP allocated to PG&E was increased because the PG&E specific LOLE increased faster relative to SCE and SDG&E.” [1]

For these reasons, PG&E strongly supports CAISO initiating and considering a robust set of scenarios in this TPP cycle to fully examine a range of solutions, including Path 26 and Path 15 upgrades as well as alternative transmission solutions.  This will ensure that sufficient energy can be delivered to PG&E’s zonal area to reliably meet forecasted post-2030 load growth.

[1] See “Mid-Term Need Determination Analysis” p. 26. https://www.cpuc.ca.gov/-/media/cpuc-website/divisions/energy-division/documents/integrated-resource-plan-and-long-term-procurement-plan-irp-ltpp/2025_09_need-determination-analysis.pdf

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

None.

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

None

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

None

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

None

5. Please provide your organization's Economic Study Requests

None

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

None

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

The follow comments are for the 2026-27 Draft Study Plan document:

1. Page 11 – it would be helpful to know if the CAISO and PGAE will include battery charging as “load” for this criterion:

2. Page 12 – An issue we’ve discussed in the past is whether the year 15 studies are subject to the same criteria (such as Cascading limits) as those “officially” within the Planning Horizon defined by NERC.  It would be nice to get some clarification there in that respect.  It is also worth noting that extending the Planning Horizon, as opposed to calling the Year 15 case a high load sensitivity, also means that violation require a CAP for the former, while they would not for the latter.

3. Page 13 – PGAE made a switch in the report this year to start calling North Bay Area as the Sonoma Area.  Not sure if that is an official name changes, but we should try to keep the study plan and reports consistent to avoid confusion.

Regarding forecasts, it’s my understanding that there will be a big change in how data center loads are modeled this year – only 67% of the capacity for signed projects will be included in the case instead of 100% of the projected load.  Seems like that should be captured in this study plan somewhere, even if it isn’t the CAISO driving that change.

4. Page 52 –Ben Williams said he may have  heard from PG&E that they want to go back to 4800 MW on Path 66 for this year’s studies?  Perhaps that’s covered by the nomogram footnote, though, but we should make sure that this table is agreed upon and that the cases will match this table.

5) Page 60 – There is conflicting information highlighted below where the Off-peak case is referred to as shoulder peak.  NERC’s Glossary has a definition for Off-peak which is also included below.  

Off-peak: Those hours or other periods defined by NAESB business practices, contract, agreements, or guides as periods of lower electrical demand.

Off-Peak cases need to meet this criteria so we can count them for TPL-001-5.1, R2.1.2 and R2.4.2.  NAESB is usually the most common definition that I have seen used since most entities do not have an Off-peak definition.  Unless CAISO and/or PGAE have their own definition, this means the load level should be between 10pm and 7am.  If we want to change that definition, it should be added to the CAISO Planning Standards and/or the study plan.

6) Page 66 – I have been pushing for years for a more standardized way to determine the multiple Facility known outages.  This is a nationwide issue in that most PC/TP’s don’t have a good way to determine these and TOP outage databases don’t usually include outages more than a year in the future.   Auditors will be looking to see how we have implemented the new requirement for V5.1, so I strongly suggest that we find a better way to identify known multiple facility outages.  Project Managers will usually have some rough ideas that we can model, but they need to be brought into the process.

7) Page 69 – I am not 100% sure how Ben Williams meant this, but Cascading is part of Table 1.  Table 1 applies to Near-Term and Long-Term, so I don’t think we can say that we are running Cascading for the Near-Term Only.  This is another example of why extending the Planning Horizon to Year 15 may bring extra requirements into play.  Of course, we may need to prepare for that scenario or at least identify if Cascading is a major problem for Year 10 and Year 15.

8) Page A-4 – these items are Static Synchronous Compensators (STATCOMs), not Static Var Compensators (SVCs):

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

Pattern Energy (Pattern) requests that the CAISO study the Main West Desert Transmission project submitted in the 2025-2026 TPP request window in the 2026-2027 TPP for economic benefits in addition to the policy and reliability benefits detailed below. The project is expected to mitigate congestion in the West of River and East of River interfaces by providing new import and export capability in the SCE Eastern and East of Pisgah areas.

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

Pattern appreciates the opportunity to provide additional comments to the California Independent System Operator (CAISO) on the 2026-2027 Transmission Planning Process (TPP) Draft Study Plan.

Pattern submitted the Main West Desert transmission project to the CAISO during the 2025-2026 TPP request window to resolve reliability impacts caused by overloads on the Colorado River Aqueduct Transmission System (CRATS). CAISO elected to continue to rely on remedial action schemes (RAS) in the SCE Eastern area to mitigate these violations long-term. Metropolitan Water District (MWD) agreed with Pattern’s identification of need, citing changes in the resource portfolios used in the CAISO’s annual TPP assessments and growing loads in the southern area of the CAISO. According to MWD, the CRATS is currently at increased risk of experiencing overloads in both frequency and magnitude. 

Additionally, Pattern has identified potential issues in the affected systems study process due to legacy agreements between MWD and CAISO. The CRATS is an integrated part of the CASIO BA in a critical resource development and import/export area, but due to legacy agreements, CAISO is not responsible for prescribing upgrades to MWD infrastructure through its annual TPP. Instead, the affected systems process allocates cost for any required upgrades to interconnecting generators.

It is evident that the issues facing MWD have been caused in-part by load growth in CAISO PTO service territories, and in-part by the very beneficial long-term grid planning done by CAISO. CAISO has encouraged resource buildout in areas electrically close to MWD - and the gigawatts of resources that have been able to interconnect by increasingly relying on operational measures and existing RAS’s to mitigate impacts to MWD’s system, but the overloads and MWD’s comments make it clear that the affected system process may fall short today, when significant solutions are required.

This presents an opportunity for collaborative solutions to the benefit of all impacted stakeholders. Therefore, Pattern requests the CAISO to evaluate the CRATS as an affected system as part of TPP studies. Pattern posits that the TPP may find that long-term planning for both to southern area load growth from a reliability perspective and for CPUC generation portfolios from a policy perspective are causing issues on MWD’s system rather than individual generators.

This proposed approach is consistent with FERC Order 1920’s desire for transmission providers to consider transmission facilities that address interconnection-related needs identified multiple times in existing generator interconnection processes but that have not been built. This would facilitate investigation of economic benefits associated Pattern’s economic study request.

Pattern seeks to bring its expertise and experience in developing, financing, constructing, owning, and operating transmission projects in the Western US to find optimal solutions and has worked with MWD to understand the CRATS and its constraints/challenges to author these comments. Pattern would pursue a future agreement with MWD to jointly develop and construct the proposed project if the project is selected for recommendation in the Board-Approved 2026-2027 TPP.

[1] Metropolitan Water District Comments on 2025-2026 Transmission Planning Process Meeting 9/24 and 9/25,10/09/2025.

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

Santa Clarita Valley Water Agency (SCV Water) appreciates the opportunity to comment on CAISO’s draft study plan. In these comments, SCV Water’s recommendations focus on two primary areas:

• Update Tables 3.3-3 and 3.3-4: To ensure alignment with the CPUC’s final TPP portfolio and identified transmission capability.
• Stakeholder Review of Mapping: To provide a formal opportunity for stakeholders to comment on the study inputs and assumptions after CAISO initially translates the CPUC’s capacity/substation mappings.

Alignment with CPUC Final Portfolio

Section 3.3 of the CAISO Draft Study Plan outlines details regarding the CPUC’s adopted portfolio of resources. Recognizing, the “Draft Editorial Note” on page 73, SCV Water advises that the CPUC finalized its TPP portfolio in late February.  The materials accompanying that decision include a table of CPUC identified transmission capability exceedances not currently fully reflected in the CAISO draft. Specifically, CAISO’s current Tables 3.3-3 and 3.3-4 appear to be missing two exceedances identified by the CPUC, including the “highly likely” Mustang-Henrietta 230kV transmission line upgrade.

SCV Water recommends the CAISO update Tables 3.3-3 and 3.3-4 in the study plan to ensure an accurate account of the CPUC’s related findings and views.  These tables are on the 2036_Exceedance_Summary and 2041_Exceedance_Summary tabs of the CPUC spreadsheet it submits to the CAISO.

Stakeholder Input on Capacity Mapping

SCV Water recommends CAISO provide stakeholders the opportunity to review and comment on the study inputs and assumptions after the initial translation of the CPUC’s capacity/substation mappings.  In previous cycles, CAISO has altered the mapped capacity during this translation phase. SCV Water believes that stakeholders should be given the opportunity to provide additional context if major capacity deviations occur from the CPUC-approved portfolio. Ensuring accuracy at this stage is critical to avoiding unintended consequences in the final study results.

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

Shell Energy appreciates the opportunity to comment on the 2026-2027 Transmission Planning Process and requests that the CAISO consider studying the implications of expiring contracts at IPP, expanding import capabilities at Lugo or Sylmar and identify a durable post-2027 import solution given the known contractual uncertainty at IPP in this timeframe. Shell Energy is an off taker from the Fervo geothermal project and has secured MIC at IPP to support resource adequacy imports to the CAISO BAA from this resource; however, we have concerns regarding the viability of IPP as a scheduling point if the STS transmission into LADWP and the generation associated arrangements expire together in June 2027. After this date, if the transmission into LADWP were to revert to LADWP and the CAISO municipal entities no longer hold these entitlements, the viability of IPP as an import point could be at risk reducing total MIC at IPP to zero. Shell Energy also requests that the CAISO, as part of this process, consider the implications caused by any encumbrances from the TransWest Express (interconnection with LADWP at IPP in 2029) and the TSR that LADWP has submitted from IPP to Sylmar (in study). Given the uncertainty associated with IPP and the significant value of MIC secured at this point to support import of contracted resources, Shell Energy asks that the CAISO consider a migration or transitional plan to convert MIC secured at IPP to Lugo if IPP is compromised.

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

Load Forecast Transparency and Bus-Level Allocation

The CAISO, CPUC, and CEC maintain a single-forecast framework for the TPP in which the 2025 IEPR is used for local studies with Known Loads and the 2024 IEPR is used for certain system studies, while Participating Transmission Owners (PTOs) derive the bus-level allocations. To enable rigorous third-party replication of reliability screens and to elicit more actionable stakeholder input, we request that the ISO publish a study-area-level allocation of the hourly load forecast for base cases and a concise methodology note documenting how PTO bus-level loads are derived from CEC type-level forecasts and modifiers, such as AAEE, AAFS, AATE, Data Servers, and Known Loads, including any normalization, loss adjustments, weather-year alignment, and balancing steps. Providing this information will allow stakeholders to test contingency outcomes with higher confidence, identify locational discrepancies early, and improve the quality of request-window submittals, particularly in Northern California study areas experiencing rapid load growth and acute Transmission Plan Deliverability (TPD) scarcity.

Additional Deliverability Scenarios to Inform Reliability and Policy Screens.

Building on CAISO’s existing winter and off-peak base cases and the on-peak HSN/SSN deliverability framework, we request inclusion of two additional deliverability scenarios within the 2026–27 scope. First, a Winter Peak deliverability scenario that reflects north-of-GBA winter conditions and evaluates voltage and thermal performance when hydro and wind patterns differ from summer HSN/SSN and solar capacity is diminished. Second, a Battery-Charging deliverability scenario that stresses import paths and area substations during high-renewable, low-load conditions when large-scale charging can shift flows and change the hours in which constraints bind.

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

Unaccounted-for TPD — Constraint-Level Computation and Publication

We request confirmation that unaccounted-for TPD will be computed at the constraint level for each binding element, consistent with the CPUC dashboard methodology. The CPUC summary of unaccounted for TPD was appropriately presented at the constraint level and showed, as an example, that the Collinsville constraint should include 3.5 GW of unaccounted-for TPD; however, the CAISO summary table suggests that the PG&E NGBA does not have significant unaccounted-for TPD, creating a discrepancy that should be resolved in the final study plan. Because area-level aggregation can mask constraint-specific shortfalls, for example at Collinsville, we further request publication, for each binding constraint, of the TPD allocated, the non-LLT FCDS portfolio at the same point of interconnection, and the resulting unaccounted-for TPD. This will ensure upgrades are properly justified where portfolio-deliverability gaps exist.

North of Greater Bay Area Constraints (Collinsville, Delavan, Tesla) and Birds Landing, Contra Costa 230 kV. Consistent with prior SCP comments, we request focused screening of Collinsville, Delavan, and Tesla constraints that have contributed to sustained TPD scarcity, and targeted evaluation of the Birds Landing-Contra Costa 230-kV interface as a potentially nested constraint affecting offshore wind, north coast resources, and geothermal integration. Where modest reinforcements or reconductoring with advanced conductors can quickly unlock deliverability, CAISO should consider policy- or economic-driven designation based on multi-value benefits, including reduced congestion and improved utilization of existing 500-kV backbones that would relieve severe scarcity of TPD in north of greater bay area.

Use of CPUC Sensitivity Portfolio for Right-Sizing

The CPUC’s Proposed Decision for the 2026–27 TPP transmits both a base and a sensitivity portfolio and directs the ISO to use the sensitivity not merely for informational purposes but to identify cost-effective upgrades and to support right-sizing where warranted. To provide a transparent record, we request that the Final Study Plan identify the decision points at which sensitivity results can influence conductor selection, transformer bank ratings, voltage class, and corridor selection, and that subsequent postings include a traceability table linking sensitivity findings to any recommended scope changes together with concise engineering rationale.

Geothermal Geographic Distribution and Portfolio

Based on the CPUC busbar mapping dashboards, geothermal volumes appear to increase in certain PG&E areas relative to prior cycles. We ask CAISO to describe explicitly how these shifts are reflected in solution screening and whether prior right-sizing assumptions in PG&E territory remain valid. A short note tying busbar changes to affected constraints and candidate mitigations would help align portfolio geography with transmission solutions.

Hilltop Intertie

The CPUC busbar mapping includes material capacity at the Hilltop (NVE) substation to facilitate instate geothermal, in-state wind, and direct Northern Nevada imports.  In supporting the CPUC’s mapping, the ISO should approve the necessary entitlements and upgrades to provide a new direct intertie at Hilltop.  The CAISO should also approve necessary downstream upgrades to facilitate import capacity sufficient to meet the CPUC portfolio objectives along with validating sufficient transfer capacity in NVE from Northern Nevada resources.

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

Linking Northern California Deliverability to Path 15 Congestion. Persistent economic congestion on Path 15 has been identified in prior cycles. We request that CAISO quantify the marginal reduction in congestion rents and CRR underfunding, and any redispatch savings, associated with incremental TPD and targeted upgrades that relieve Collinsville, Delavan, and Tesla constraints. Where multi-value benefits are demonstrated, deliverability improvement together with congestion relief and operational flexibility, we encourage consideration for policy- or economic-driven approval consistent with TEAM.

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

 We are not submitting a separate economic study request at this time.

5. Please provide your organization's Economic Study Requests

We are not submitting any Frequency Response comments at this time.

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

Sonoma Clean Power is submitting this request on behalf of California Community Power (CC Power).  CC Power is representing the following eight Community Choice Aggregators (CCAs) that are also CAISO Load Serving Entities for the following two requests: Central Coast Community Energy, Silicon Valley Clean Energy, CleanPowerSF, Peninsula Clean Energy, Sonoma Clean Power, San Jose Clean Energy, Valley Clean Energy, and Redwood Coast Energy Authority.

Per Section 3.2.6 of the Transmission Planning Process Business Practice Manual, the LSEs in CC Power are requesting MIC expansion to accommodate long-term geothermal Resource Adequacy resources.  CC Power made a similar request in 2024. CC Power is requesting the CAISO reevaluate the ability to expand MIC in the 2026-2027 TPP given changes in the CC Power portfolio, potential improvements in transmission capability, and to ensure continuous study of previously requested MIC expansions.

Please contact Amit Ranjan from Sonoma Clean Power for more information.

Amit Ranjan

aranjan@sonomacleanpower.org

(707) 729-1065

MIC EXPANSION REQUEST 1

Branch Group/Delivery Points and Qualifying Capacity MW

IID-SDGE_ITC (IVLY2): 16.83 MW

Ormat is providing CC Power with 63 MW of geothermal capacity deliverable to IID-SDGE_ITC (IVLY2).  CC Power has collectively secured 46.17 MW of RIC, but is requesting a MIC Expansion to accommodate the 16.83 MW that is not yet secured.

Supplier

Ormat

Resource Name/Market ID and Resource Type

Ormat Geothermal

Initial Date Contract was entered into or expected to be entered into

An RA contract was executed on May 31, 2022 with Ormat.

Expected Delivery Start Date and Term of Contract

Expected COD for the resource needing incremental MIC is Q4 2028.  The contract term is 20 years.

Contract Type Description

CC Power has signed an RA contract with Ormat for a total of 125 MW.

MIC EXPANSION REQUEST 2

Branch Group/Delivery Points and Qualifying Capacity MW

SILVERPK_ITC(SILVERPEAK55): 16.8 MW

CC Power is requesting the CAISO study 16.8 MW of MIC expansion at Silver Peak to provide a delivery option if Greenlink West is delayed.  CC Power is contracted to receive power at Eldorado 230, where MIC is secured, after Greenlink West is online.

Supplier

Open Mountain Energy (OME)

Resource Name/Market ID and Resource Type

Geothermal Facilities Fish Lake Geothermal

Initial Date Contract was entered into or expected to be entered into

An RA contract was executed on May 31, 2022 with Open Mountain Energy for 13 MW and is being amended to reflect 3.8 MW of additional capacity.

Expected Delivery Start Date and Term of Contract

Expected COD on April 30, 2027. The term will be 20 years but CC Power will only need MIC at Silver Peak until Greenlink West is online.

Contract Type Description

CC Power has signed an RA contract with OME for 13 MW, which is being amended to reflect 16.8 MW.

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

  We are not submitting a separate economic study request at this time.

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

Viridon Path 15 LLC respectfully requests that the CAISO conducts economic studies in the 2026-2027 Transmission Planning Process to assess the benefits of upgrading the Los Banos–Gates #3 500 kV line to alleviate Path 15 congestion. The proposed solutions, described in the attached economic study request document, include and combine the following reinforcement options:

• Addition of series compensation on LBG3 (70%)
• Reconductoring of LBG3 with advanced conductor
• Tap into the Manning substation
• SmartValve power flow control on LBG3

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting

1. Please provide your organization's comments on the Draft Study Plan Reliability Assessment

2. Please provide your organization's comments on the Draft Study Plan Policy Assessment

3. Please provide your organization's comments on the Draft Study Plan Economic Assessment

4. Please provide your organization's comments on the Draft Study Plan Frequency Response Assessment

5. Please provide your organization's Economic Study Requests

The WATT Coalition respectfully requests that the California Independent System Operator (CAISO) conduct two economic planning studies: 1) investigate Grid Enhancing Technologies (GETs) opportunities identified by market participants and in California utilities’ SB1006 reports and 2) study the full CAISO transmission system for opportunities to deploy GETs to reduce congestion and improve system efficiency. 

The WATT Coalition is a trade association of GETs companies, renewable energy developers, clean energy financiers, and utilities working to lower energy costs, improve reliability and accelerate clean energy deployment through grid modernization and efficiency. Example WATT members who are market participants in the CAISO include EDF Power Solutions and Invenergy. Comments by the WATT Coalition do not necessarily reflect the views of all WATT members. 

Grid Enhancing Technologies—including Dynamic Line Ratings (DLR), Advanced Power Flow Controllers (APFC), and Transmission Topology Optimization (TTO)—optimize the use of existing transmission infrastructure by increasing transfer capacity, improving the management of power flows, and enabling operators to utilize transmission assets more effectively. These technologies have been deployed across the world and have demonstrated the ability to unlock significant additional transfer capacity on existing transmission infrastructure to reduce congestion costs. 

Transmission congestion remains a persistent challenge on the CAISO system. In recent years, congestion costs in CAISO have approached or exceeded $1 billion annually, topping $1.04 billion in 2023 and reaching $734 million in 2024 alone. While congestion data for 2025 have not yet been published, the CAISO Department of Market Monitoring reported a 69% increase in day-ahead market congestion rents on internal and intertie transmission constraints in Q3 2025 compared to Q3 2024. These high congestion costs reflect insufficient transmission capacity to deliver the cheapest, cleanest energy in California. These constraints will also impede new generation and load seeking grid interconnection. The CAISO’s economic planning in the Transmission Planning Process should look for low-cost, fast-to-implement GETs solutions to expensive and persistent grid constraints.  

A growing body of analysis and operational experience shows that GETs can meaningfully increase transmission capacity and reduce congestion costs. The Brattle Group’s Unlocking the Queue analysis found that deploying GETs across the bulk power system could double the capacity available for new resources in parts of the Southwest Power Pool—from 2.6 GW to 5.2 GW—while reducing curtailment and congestion, with the GETs deployments paying for themselves within months. According to the CPUC, 13.2 GW of renewable generation and storage resources currently in development have already been delayed or are at risk of delay due to delayed transmission project timelines. Scaling the results of Unlocking the Queue in SPP implies that GETs can provide multiple gigawatts of capacity to help speed up interconnection processes for these renewable resources in California that face development delays.  

Operational deployments across the world have produced similar results. In the United Kingdom, APFC unlocked 2 GW of additional capacity across three substations, and other individual deployments have found 100-500MW of capacity. Belgium’s system operator Elia has operated with DLR since 2012, finding 10-16% percent or more capacity gains 90% of the time. TTO found 7% additional transfer capacity for a utility in South America. A 7% increase in transfer capacity on the CAISO system under 2025 peak load conditions could translate into over 3 GW of additional capacity. Increasing CAISO’s 33,000-mile transmission system by 7% with traditional transmission expansion would cost more than $2.3 billion, while TTO could potentially achieve a similar capacity increase with software alone.  

It is critical that CAISO investigate GETs for cost savings and speed of deployment, to reduce costs while a larger regional infrastructure is built. Unlocking the Queue found that the identified $90 million in GETs deployments in the study would pay for themselves in six months of operational savings. When we use the term “cost-effective” in these comments, we generally expect CAISO to find payback periods of six months to two years, not traditional multi-decade timelines for transmission investments. 

Request 1: Evaluate GETs deployments identified by utilities and market participants that will likely cost-effectively reduce congestion 

California Senate Bill 1006, enacted in 2024, required transmission utilities to evaluate whether Grid Enhancing Technologies could help improve grid performance across several key objectives, including increasing transmission capacity, reducing congestion, reducing renewable curtailment, improving reliability, and expanding the ability to interconnect new clean generation. 

In response, California’s investor-owned utilities submitted reports in late 2025 that evaluated and identified potential opportunities to deploy GETs across portions of their transmission systems. These evaluations surfaced several candidate projects and corridors where GETs could provide operational or economic benefits. For example, SCE’s analysis found nine candidate circuits where DLR could increase line capacity, stating that these lines could serve as “a starting point for CAISO’s review as part of its annual transmission planning process for economic, reliability, and policy goals.” PG&E similarly identified 14 lines as candidates for further evaluation by CAISO. 

We also recommend that CAISO study opportunities raised by other stakeholders for GETs to reduce congestion. For example, in December 2025, Viridon requested that CAISO evaluate a set of GET-based solutions to address congestion on the Path 15 corridor, which CAISO has identified as a high-priority economic study area. Under CAISO’s 2035 base portfolio, Path 15 is projected to face more than $1.2 billion in annual congestion. Viridon proposed evaluating several solutions, including SmartValve power flow control devices, and conducted preliminary economic and transfer capability analysis, indicating that these GETs-based solutions could reduce congestion, lower renewable curtailment, increase system throughput, and deliver meaningful economic benefits.

3. Request 2: A CAISO system-wide study could identify additional GETs deployments with potential to save over $200 million year over year 

While the SB 1006 reports and stakeholder suggestions provide a useful starting point for identifying GET deployment opportunities, the analyses were not exhaustive, and did not look at optimization potential across utility seams or in complex pathways. There are likely many more cost-effective GETs opportunities in California. A CAISO study could complement this work by evaluating GET opportunities across larger portions of the grid and broader considerations of system value. A system-wide study should start with looking for opportunities for the greatest congestion relief, but could also include production cost savings from renewable integration or beyond. Studies and deployments have shown that GETs can reduce transmission congestion by 40% or more in some cases. Given that CAISO experienced $734 million in congestion costs in 2024, reductions of this scale could imply potential savings on the order of $293 million if similar impacts were realized across affected constraints. 

1. Methodology example: time-series power flow and contingency analysis for Dynamic Line Ratings 

One way CAISO could evaluate potential DLR deployments as part of this proposed system-wide economic study is through conducting a time-series power flow and contingency analysis similar to the methodology used by AES Corporation in its synthetic WECC case study. This approach evaluates Dynamic Line Ratings under diverse loading and generation conditions across an entire year, rather than relying on a single peak-hour planning case, allowing planners to identify both where and when transmission constraints could be addressed with DLR. 

Under this framework, CAISO could construct hourly system snapshots for the study year using hourly load and renewable generation data. For each hourly case, CAISO could run a baseline power flow and N-1 contingency analysis to identify overloaded lines and the contingencies driving those constraints. This screening step helps identify candidate lines where additional transmission capacity could provide value. 

Weather-adjusted line ratings could then be calculated for candidate lines using standard conductor heat-balance methods, such as those described in IEEE Std 738-2023. These calculations incorporate weather inputs including ambient temperature, wind speed, wind direction, and solar radiation to determine hourly line ratings that reflect actual operating conditions. 

Finally, the power flow and contingency analysis could be re-run using the updated line ratings. Comparing the baseline and DLR cases would allow CAISO to quantify the potential benefits of deployment, including reductions in thermal overload hours, congestion, renewable curtailment, and improvements in transmission transfer capability. 

2. Methodology example: integrated, system-wide evaluation of GETs based on the Unlocking the Queue framework 

CAISO could also evaluate the combined impact of multiple GETs using a methodology similar to the one used in Brattle’s Unlocking the Queue with Grid-Enhancing Technologies study. That study followed a defined five-step process to analyze how much additional renewable generation capacity could be added to the grid using GETs. While the Brattle study’s exact objective was to find capacity for generation in the SPP interconnection queue, a CAISO application of the methodology could instead focus on economic outcomes such as congestion reduction and production cost savings. 

The Brattle framework begins by identifying areas where GET deployment is most likely to deliver meaningful system benefits, such as regions with persistent congestion, renewable curtailment, or significant volumes of queued generation. The study then selects a set of representative operating conditions intended to capture a full year of system operations. Historical operating cases are modified to reflect the planning horizon by incorporating expected load growth, transmission upgrades, generation additions, and resource retirements. 

For each representative case, Brattle solved two cases across the entire transmission network to find the maximum amount of renewables that could be integrated under (1) a business-as-usual scenario (“Base Case”) and then (2) with GETs (the “With GETs” Case). In the “With GETs Case,” Brattle layered the technologies sequentially—DLR, Advanced Power Flow Control then Topology Optimization, and a finally pass for DLR to see if the APFC and reconfigurations found further opportunities for DLR.  Comparing a “Base Case” and “With GETs” scenario would allow planners to quantify benefits such as reduced congestion, lower production costs, reduced renewable curtailment, and increased transmission transfer capability, and see whether the GETs deployment would be cost effective. 

4. Expected benefits 

A CAISO economic planning study evaluating Grid Enhancing Technologies could provide several benefits for the CAISO system and California ratepayers. 

First, GET deployments have the potential to reduce congestion costs by increasing transfer capability and improving the management of power flows across the transmission networks, thereby lowering electricity costs for consumers. 

Second, GETs can help meet the increasingly urgent timeline for interconnecting new renewable resources. To capture the full value of federal tax credits, many clean energy projects must come online by 2027, creating a narrow window for California to connect as much new generation as possible. At the same time, many renewable resources are located in areas where transmission capacity is constrained, leading to curtailment or deliverability limitations. Grid Enhancing Technologies can help address this challenge by increasing transfer capability on existing transmission infrastructure. By unlocking additional headroom on the grid, GETs can allow more renewable generation to reach load centers, reduce curtailment, and help California bring new clean energy online more quickly while longer-term transmission projects are developed. 

Third, GETs can improve the utilization of existing transmission infrastructure. By increasing the effective capacity of existing lines or optimizing power flows across the network, these technologies can provide additional headroom on the grid while longer-lead transmission projects move through planning, permitting, and construction. 

Finally, GETs can enhance operational flexibility for grid operators, providing operators with additional tools to respond to changing system conditions, including outages, shifting generation patterns, and evolving load profiles. 

The WATT Coalition appreciates the opportunity to submit this Economic Planning Study Request as part of the 2026–2027 Transmission Planning Process Draft Study Plan. The WATT Coalition respectfully encourages CAISO to, as part of the 2026–2027 Transmission Planning Process, 1) investigate GETs opportunities identified by market participants and in California utilities’ SB1006 reports and 2) conduct an economic planning study evaluating the deployment GETs across the CAISO transmission system to reduce congestion and improve system efficiency. 

6. Please provide your organization's Maximum Import Capability (MIC) expansion requests. Any confidential details should not be included in this comment template and should instead be emailed to regionaltransmission@caiso.com

7. Please provide any additional comments on the Draft Study Plan and February 24th, 2026 Stakeholder Meeting