Comments on Nov 12 Hybrid Meeting, Working Group Session 10: Uplift and Default Energy Bids (DEB), State-of-Charge Management, and Mixed-Fuel and Distribution-Level Resources

1. Please provide a summary of your organization's general comments on the materials shared and subsequent discussion during the Nov 12 meeting.

The California Community Choice Association (CalCCA) appreciates the opportunity to comment on the California Independent System Operator’s (CAISO) Storage Design and Modeling Working Group Meeting. In summary, the CAISO should:

• Adopt CalCCA’s alternative resource adequacy (RA) accounting proposal for storage resources with foldback included in their PMax, if the CAISO puts forth a proposal in the California Public Utilities Commission’s (CPUC) RA proceeding;
• Prioritize the development of a Master File parameter as a market-based solution to reflecting foldback in the market and ensuring known resource characteristics are modeled rather than reflected in a resource’s unforced capacity value;
• Adopt the stakeholder-supported, principle-based approach in which negative revenues attributed to market algorithms or CAISO action may warrant uplift and negative revenues attributed to bidder behavior may not warrant uplift; 
• Require the submission of the day-ahead initial state-of-charge (SOC) parameter within a certain accuracy range to be eligible for bid cost recovery (BCR); and
• Do not exempt storage resources from local Market Power Mitigation (MPM) and instead seek to enhance the tools and methodologies used to manage storage resources in the market and provide uplift payments when warranted.

2. Provide your organization’s comments regarding the initiative’s overview and schedule.

CalCCA has no comments at this time.   

3. Provide your organization’s comments regarding the update on nonlinearity.

The CAISO’s proposed path forward addresses two issues: (1) reflecting foldback in the CPUC RA qualifying capacity (QC) calculation; and (2) reflecting foldback in CAISO market optimization.

The CAISO should adopt CalCCA’s alternative RA accounting proposal for storage resources with foldback included in their PMin to PMax range if the CAISO puts forth a proposal in the CPUC’s RA proceeding. CalCCA understands that the CAISO plans to propose a QC methodology that accounts for foldback in the CPUC’s Rulemaking (R.) 25-10-003, on January 23, 2026. The CAISO’s proposed calculation would divide the amount of energy the resource can provide unaffected by foldback by four (for a four-hour battery). This will discount the RA counting for the resource for all hours it can be shown. This is not reflective of the nature of foldback and would overly constrain the RA value a resource can provide in the hour of greatest need.  This is particularly important given the slice-of-day (SOD) nature of the CPUC RA system in which an LSE must demonstrate sufficient capacity to serve load in all 24 hours of the “worst day” of the month.  Using an average rather than values that can be provided will unnecessarily discount resources in some hours in which the resource is available to reliably serve grid needs.

Instead, if the CAISO makes a proposal in the CPUC’s RA proceeding to account for foldback in the CPUC’s QC calculation, it should modify its proposed calculation to allow a resource to count for full capacity for three of the four hours and a derated amount in the fourth hour. Under the SOD framework, an LSE can claim the full amount of capacity for a single hour but may not need the full capacity in other hours. CalCCA’s proposed alternative calculation would result in a higher RA counting in the hour of highest need, and more accurately reflect the impacts of foldback on RA capacity.

The example below compares the CAISO’s proposal with CalCCA’s proposed alternative assuming a resource with a 25 megawatts (MW) nameplate, 90 megawatt hours (MWh) available, and 10 MWh unavailable due to foldback.

• The CAISO’s proposed calculation
  • NQC = 90MWh/4 hours = 22.5 MW
  • SOD Showing: No greater than 22.5 MW in any hour
• CalCCA’s proposed alternative
  • NQC = 25 MW
  • SOD Showing: MW in hour 1 + MW in hour 2 + MW in hour 3 + MW in hour 4 cannot exceed 90 MWh

Under CalCCA’s alternative proposal, the NQC will equal 25 MW (nameplate), and the total energy in all hours shown will not exceed 90 MWh. In this case, that means the resource can be shown for 25 MWs in hours 1 – 3, resulting in a total of 75 MWh and leaving 15 MW available for the fourth hour. The result is a maximum amount of 25 MW in any hour, limited by energy. Under this proposal, an LSE could show the resource for 22.5 MW in each hour and get the same result as the CAISO’s proposal but could also show up to an addition 2.5 MWs in three hours from the resource as long as the total showing does not exceed the resource’s energy limit. If the CAISO proposes derating a resource’s capacity value to account for foldback, it should do so using CalCCA’s alternative proposal and apply it only to resources whose PMax includes the foldback range.

This proposal will also work for resources that are not constrained by foldback.  For example, if the resource has a 25 MW peak capacity and sufficient storage to provide 110 MWh, then the foldback never occurs and the energy limit is never reached meaning that the resource can be counted for 25 MWs in all four hours. 

Market Optimization

The CAISO should prioritize the development of a Master File parameter as a market-based solution  reflecting foldback in the market and ensuring known resource characteristics are modeled rather than reflected in a resource’s unforced capacity value. The CAISO proposes an interim and long-term proposal for addressing foldback in the market optimization. The interim proposal would result in the market optimization being unable to access the resources’ foldback range. As described in section 4, below, unnecessarily making energy in the foldback range unavailable to the market when foldback ranges are not static is a negative outcome for reliability, ratepayers, and storage owners.

Any interim approach should continue to allow the market to access the foldback range, when the resource is available within that range. A better alternative would be to maintain the status quo in the interim, in which storage resources reflect foldback ranges with outage cards and prioritize the CAISO’s long-term solution of a Master File parameter to reflect foldback in the market. CalCCA has previously advocated for the “Technical Limitations Not in the Market Model” Resource Adequacy Availability Incentive Mechanism (RAAIM) exempt outage card to be used and continues to support that approach for the reasons described in CalCCA’s September 5, 2025, comments.[1] More important than the type of outage card used in the interim, however, is prioritizing a Master File parameter as a market-based solution to reflecting foldback in the market and ensuring known resource characteristics are modeled rather than reflected in a resource’s unforced capacity value.

[1]            https://stakeholdercenter.caiso.com/Comments/AllComments/a35d7182-e62e-4559-93c0-80ede736ceba#org-a3c4805c-db85-45ec-b58c-a9ccff090a32.

4. Provide your organization’s comments regarding the presentation offered by REV Renewables.

CalCCA agrees with Rev Renewables that unnecessarily making energy in the foldback range unavailable to the market when foldback ranges are not static is a negative outcome for reliability, ratepayers, and storage owners. As stated in section 3, the CAISO should prioritize developing Master File fields for resources to reflect foldback ranges in the market model.

5. Provide your organization’s comments regarding the guiding principles related to the Uplift & Default Energy Bid (DEB) topic group.

CalCCA supports the CAISO eliminating opportunities for strategic bidding to inflate BCR payments. CalCCA agrees with the stakeholder-supported, principle-based approach in which negative revenues attributed to market algorithms or CAISO action may warrant uplift, and negative revenues attributed to bidder behavior may not warrant uplift. 

6. Provide your organization’s comments regarding the responses on Day-Ahead Uplift and Initial State-of-Charge (SOC) as part of the Uplift & Default Energy Bid (DEB) topic group.

CalCCA reiterates its October 13, 2025, comments.[1] Specifically, the CAISO’s solution should adhere to the principle, rather than institute a blanket elimination of day-ahead BCR, unless the CAISO can demonstrate all cases of day-ahead BCR are driven by scheduling coordinator action rather than CAISO market or operator action.

CalCCA directionally supports the CAISO’s proposal to require the submission of the day-ahead initial State of Charge (SOC) parameter within a certain accuracy range to be eligible for BCR. In general, scheduling coordinators (SC) should be responsible for accurately reflecting their resources’ characteristics rather than relying on a default value. CalCCA supports adopting a mechanism to incent submissions within a pre-defined accuracy range, though it does not take a position on which proposed mechanism should be adopted among the CAISO, California Energy Storage Alliance, and Vistra Corp. (Vistra) proposals.[2] If an SC does not select a value despite the requirement to do so, then the CAISO should include a default value. If the default value is outside the accuracy range, the resource should be ineligible for uplift.

[1]            https://stakeholdercenter.caiso.com/Comments/AllComments/c9903a4c-a900-47d2-b362-51c768a52e73#org-57fb586b-0cfd-4b02-a180-1b0262593a0f.

[2]            Storage Design and Modeling, Working Group on Outage Management, Uplift & DEB and Mixed-Fuel & Distribution Level Resources (Nov. 14, 2025) (CAISO Presentation), at Slide 45.

7. Provide your organization’s comments regarding Real-Time Uplift and Proposed Approaches as part of the Uplift & Default Energy Bid (DEB) topic group.

CalCCA supports a real-time uplift approach aligned with the principle discussed in section 5, above. The data provided by the CAISO and the Department of Market Monitoring clarifies the magnitude of out-of-merit dispatches resulting from the multi-interval optimization (MIO) and the comparison of net revenues under the MIO and a counterfactual no-MIO scenario. The overall BCR methodology for storage should consider MIO out-of-merit dispatches and provide resources make-whole payments if they experience net losses over the day. However, a specific uplift payment for MIO out-of-merit dispatches without consideration of net losses over the day, as suggested by some stakeholders, is unnecessary and unsupported.

Instances of MPM may warrant uplift if a resource bids to preserve its output until later in the day, but the bid is mitigated, causing the resource to be dispatched when it otherwise would not have been. On the other hand, instances of MPM may not warrant uplift if the resource is rightfully mitigated to avoid the abuse of market power. For the reasons described in section 11, the CAISO should not cease local MPM for storage assets as a means to eliminate the need for a real-time uplift mechanism because MPM plays a role in protecting ratepayers from the exercise of market power.  

8. Provide your organization’s comments regarding the notion of establishing a form of System SOC target or constraint, including your perspective on how the SOC target should be established and the relationship this target or constraint would have with market products.

CalCCA has no comments at this time.

9. Provide your organization’s comments regarding the potential modifications to the storage DEB to enable the representation of real-time conditions and ease its use across different geographies.

CalCCA has no comments at this time.

10. Provide your organization’s comments regarding the presentation offered by Pacific Gas & Electric (PG&E).

CalCCA has no comments at this time.

11. Provide your organization’s comments regarding the presentation offered by Vistra, including the discussion questions included in their materials.

CalCCA appreciates Vistra’s presentation and acknowledges the challenges with managing use-limited storage resources in the CAISO market. However, CalCCA does not support exempting storage resources from local MPM under Vistra’s proposed self-management option. MPM is a critical component of the CAISO’s market design to prevent suppliers from exerting market power, maintain competitive market outcomes, and ensure just and reasonable rates for customers. While there are other resource types to which MPM is not applied, these resources are: (1)  not fully integrated into the CAISO market (e.g., certain investor-owned utility-run load reduction programs); (2) called upon only in emergencies (e.g., reliability demand response resources); (3) bid but based on the value to load, with bids being struck primarily where other marginal cost based supply has run out or load is willing to curtail at a price lower than the marginal resource (e.g. proxy demand response); or (4) should be subject to MPM pending the development of a DEB (e.g., hybrid resources). The CAISO should therefore seek to enhance the tools and methodologies used to manage storage resources in the market and provide uplift payments without exempting the technology from MPM.   

12. Provide your organization’s comments regarding the presentation offered by Cong Chen Ph.D., Assistant Professor, Thayer School of Engineering, Dartmouth College.

CalCCA has no comments at this time.   

13. Provide your organization’s comments regarding the update provided regarding the high sustainable limit (to ease the development of comments, please note that a more detailed review of the proposed guidance is included in the materials presented September 29, 2025).

https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

CalCCA has no comments at this time.  

14. Provide your organization’s comments regarding the update and materials on outage reporting for distribution-level resources. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4)

CalCCA supports the CAISO’s proposed changes to this element.   

15. Provide your organization’s comments regarding the materials and upcoming discussion on the co-located variable energy resource Follow DOT topic. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

CalCCA has no comments at this time.   

16. Provide your organization’s comments regarding the upcoming discussion on mixed-fuel ancillary services. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

CalCCA has no comments at this time.   

17. Please provide any additional comments, feedback, or examples in the Nov 12 stakeholder meeting. You may upload examples or data using the Attachments field below.

CalCCA has no additional comments at this time.   

1. Please provide a summary of your organization's general comments on the materials shared and subsequent discussion during the Nov 12 meeting.

Comments on Storage Design and Modeling

Working Group Presentation on November 12, 2025

Department of Market Monitoring

November 26, 2025

Summary

The Department of Market Monitoring (DMM) appreciates the opportunity to comment on the Storage Design and Modeling working group presentation held on November 12, 2025.[1]

DMM appreciates the ISO’s attention to storage bid cost recovery (BCR) issues. DMM continues to support eliminating day-ahead (DA) BCR for storage resources unless specific instances are identified where DA BCR is clearly appropriate to support efficient market outcomes for storage resources.[2] DMM continues to recommend a similar approach to establishing real-time (RT) BCR eligibility for storage resources, with a default of no BCR, and eligibility for RT BCR only established under specific situations when it is deemed appropriate. Specifically, DMM recommends the ISO eliminate RT BCR for storage resources buying back day-ahead schedules due to insufficient state-of-charge (SOC) by default, only allowing this source of RT BCR in specifically identified situations deemed appropriate.

If the ISO instead chooses to maintain default eligibility of batteries for RT BCR, and attempts to address each individual scenario that could lead to unwarranted RT BCR, DMM supports the proposal to reduce day-ahead buybacks due to insufficient SOC by better incentivizing accurate submissions of the DA initial state-of-charge (DA ISOC) parameter. Even if the DA ISOC is accurate, there is still a bidding incentive issue if storage resources receive BCR for day-ahead buybacks due to insufficient SOC. DMM supports the ISO requiring DA ISOC submission independent of the BCR issues. DMM recommends strengthening the tariff language to better define expected use of the DA ISOC in order to promote reliability and discourage misuse of this parameter.

The system state-of-charge mechanism introduced by the ISO appears to be another potential proposal aimed at reducing day-ahead buybacks due to insufficient state-of-charge. However, this approach also does not address the underlying BCR design issue, and DMM requests more information about this mechanism and how it is different than the minimum SOC constraint that was retired in 2023.

DMM supports enhancements to the storage default energy bid (DEB) and continues to recommend an hourly DEB for storage resources that reflects estimated intraday opportunity cost associated with future intervals and changing real-time conditions.[3]

DMM supports the ISO’s proposal to require storage resources to provide Master File parameters that reflect a qualifying capacity (QC) where the resource can discharge for four hours or more without expected power limitations (e.g., foldback). Further, DMM recommends the ISO introduce additional Master File parameters that allow for the additional energy within the resource to be available to the market during extenuating circumstances if the market or market operators were to need to access the stored energy.

Comments

DMM supports the ISO addressing storage bid cost recovery issues as a top priority. DMM continues to recommend redesigning storage BCR rules to assume no eligibility, and only add eligibility under specific situations where it is deemed appropriate and necessary to support market efficiency.[4]

DMM supports elimination of day-ahead BCR for storage resources

DMM supports the ISO’s proposal to eliminate DA BCR for storage resources. The ISO and stakeholders have not demonstrated that DA BCR for storage resources is necessary to support market efficiency. Further, the current DA BCR design can lead to unwarranted BCR payments and is susceptible to gaming. DMM recommends the same bottom-up approach be taken to establish rules for real-time bid cost recovery.

DMM continues to recommend that storage resources only be eligible for RT BCR under specific situations where deemed appropriate

Allowing storage resources to receive BCR for day-ahead buybacks due to insufficient state-of-charge removes their exposure to real-time prices and fails to incentivize efficient bidding for storage resources in the real-time. Many of the potential policy changes discussed by the ISO aim to minimize day-ahead buybacks due to insufficient SOC, but do not address the underlying issue that storage resources would still receive unwarranted BCR whenever these types of day-ahead buybacks do materialize.

As DMM has previously noted, allowing real-time bid cost recovery for day-ahead buybacks due to insufficient state-of-charge (SOC) can lead to inefficient bidding incentives and market outcomes.[5] DMM continues to recommend that storage resources only be eligible for RT BCR under specific situations where deemed appropriate.

If the ISO instead chooses to try to identify and address each different scenario that could lead to unwarranted RT BCR, DMM supports the consideration of proposals for limiting day-ahead buybacks due to insufficient SOC. DMM has found this to be the major driver of unwarranted BCR in the real-time market. Based on DMM’s monitoring over the last few years, DMM cautions that it will be challenging to identify and develop settlement rules to effectively prevent all the different causes of unwarranted BCR ex ante. In many cases, DMM has only been able to identify causes of unwarranted BCR ex post after detailed investigation of the interaction of market software features, market and operational conditions, and how settlement rules are applied.

DMM supports the ISO’s proposal to better incentivize accurate submission of day-ahead initial state-of-charge parameters. And DMM recommends strengthened tariff language to better define how the day-ahead initial state-of-charge should be used.

DMM supports the ISO’s proposal to address the current lack of incentive for storage resources to submit accurate DA ISOC parameters. While DMM supports the ISO’s specific proposals of requiring the submission of the DA ISOC in order to submit DA bids and making battery resources ineligible for RT BCR if their DA ISOC is sufficiently incorrect, DMM continues to recommend the ISO achieve this by removing RT BCR eligibility for day-ahead buybacks due to insufficient SOC. Even if resources submit accurate DA ISOC estimates, continuing to provide RT BCR for day-ahead buybacks due to insufficient SOC still results in inefficient bidding incentives and inefficient dispatch of storage resources in real-time.

Outside of the BCR context, DMM supports the ISO requiring the submission of DA ISOC for reliability purposes. DMM also supports strengthening the tariff language to better define expected use of DA ISOC, highlighting that it should be used to reflect a physical expectation of how the resource will be positioned in real-time at the beginning of the operating day, and explicitly state that it is not to be used solely for the purpose of effectuating a desired day-ahead schedule for economic purposes.

DMM requests more detail regarding the system state-of-charge mechanism mentioned in the presentation

The ISO’s presentation briefly introduced the concept of a system state-of-charge mechanism that would improve alignment between the SOC modeled in the day-ahead market and the telemetered SOC.[6] DMM’s understanding is the ISO is considering this mechanism as another potential avenue to minimize day-ahead buybacks for storage resources due to insufficient state-of-charge.

It is unclear whether this is the most efficient approach as it does not address real-time bidding incentives to manage SOC. DMM continues to recommend re-designing the BCR paradigm for storage resources so that they are properly incentivized to bid in a way that positions storage resources efficiently in the real-time. A system SOC mechanism does not address the underlying BCR design issues. DMM requests that the ISO provide additional information about this potential mechanism, and how it is different than the minimum state-of-charge constraint that was retired in 2023.

DMM supports enhancing the storage DEB to an hourly value that incorporates intraday opportunity costs

DMM has long recommended the storage DEB be refined to better incorporate real-time intraday opportunity costs. DMM has previously noted issues with the current storage DEB.[7] In particular, the DEB is static and therefore does not account for how intraday opportunity costs change across the day. In addition, the utilization of day-ahead prices does not account for differences that can materialize between the day-ahead and real-time and therefore may not be the most appropriate basis to estimate real-time intraday opportunity cost.

DMM continues to recommend the ISO implement a storage DEB that varies hourly so that it can incorporate the changing intraday opportunity cost associated with potential charge and discharge opportunities in future intervals.[8] An accurate hourly DEB would account for market conditions in future intervals when estimating the opportunity cost component of a particular hour. DMM recommends the ISO develop hourly DEBs that would allow the DEBs to be higher in the intervals leading up to the peak pricing hours, and lower in later intervals as intraday opportunity costs fall.[9]

In addition, a storage DEB that varies hourly would be necessary for the type of framework proposed by the California Energy Storage Alliance (CESA). DMM has discussed how storage resources may incorrectly be eligible or ineligible for BCR depending on DEBs that are incorrectly high or low.[10]

DMM recognizes that developing an approach that allows dynamic adjustments to battery DEBs in real-time could involve significant design and implementation complexities. Therefore, DMM recommends that the ISO and stakeholders pursue an incremental approach. A key software change that could be implemented expeditiously includes simply allowing real-time DEBs to vary for different time periods of the day, so that greater “headroom” is provided during the hours prior to the peak net load hours (12-17), compared to the level of “headroom” that is provided during the peak net load hours (18-22). A second key software change would be to allow real-time battery DEBs that are set based on day-ahead prices to be scaled upwards during the operating day based on actual market and system conditions.

Mitigation of storage resources should not be eliminated, as suggested by some stakeholders

While some stakeholders have suggested eliminating mitigation of storage resources, DMM does not believe this would be an appropriate market rule change. Storage resources should continue to be subject to market power mitigation where the potential for uncompetitive conditions exists. The establishment of more dynamic DEBs considering real-time conditions reduces the risk of mitigation to values that do not reflect real-time opportunity costs.

While the ISO’s presentation mentions that charging bids are subject to mitigation due to the need for monotonically non-decreasing bid curves, there are other reasons these bids are subject to mitigation including the flow effects of charging schedules on potentially uncompetitive constraints. Counterflow is provided when a resource forgoes charging. Uneconomically high bids to charge can worsen congestion by withholding this counterflow of foregone charging; therefore, mitigating those charging bids can relieve congestion by reducing uneconomic charging schedules.

DMM supports updating Master File characteristics for storage resources to reflect the stored energy available to the market to maintain full capacity of the resources across its operational range

The ISO is proposing that storage resources be “right sized”, whereby the parameters of storage resources provided to Master File reflect a qualifying capacity (QC) so that the resource can discharge for four hours or more without expected power limitations (e.g., foldback).^[11] For resources in the CAISO balancing area, QC is determined by the California local regulatory authorities (LRAs). The proposal directs the LRAs to ensure that the QC of the resource is based on the SOC range that will not result in power limitations from physical (chemical) SOC constraints. The “right sizing” changes mean that in Master File the resource will only reflect the minimum and maximum continuous energy limit that will best ensure resources do not experience power limitations because of the resource’s SOC.^[12]

The ISO states the change in resource QC will ensure consistency across all assets, minimize reliability and operational concerns, eliminate the need to use outage cards and be assessed resource adequacy availability incentive mechanism (RAAIM), and incorporate the power limitations into any future capacity constructs such as the unforced capacity (UCAP) adjustment to QC.^[13] This change will effectively reduce the capacity and energy of storage resources that are available to the market, as well as reduce the QC that the asset owners will be able to sell to load serving entities as resource adequacy.

DMM has previously recommended the ISO create clear rules for storage resources experiencing power limitations in the extremes of their SOC.^[14] DMM recommendations have emphasized that the rules must require that resources be assessed RAAIM and consider any future policies that would reflect capacity limitations to the market (e.g., UCAP). As a result, DMM supports the ISO requiring resources to only provide the operational characteristics of the resource in Master File that meet the capability of the resource. However, as discussed below, there are solutions to allowing access to the stored energy in the extremes of the SOC ranges to continue to provide grid services and reliability.

Reducing the operational range and adjusting the QC of some of the storage resources on the CAISO system will ensure the purchased resource adequacy (RA) of the storage resources can be expected to perform at their full power output when dispatched. As argued by REV Renewables, the reduction in the available SOC range may lead to adverse impacts on reliability, ratepayer costs, and storage owners.^[15] DMM does not agree with this position, and would like to refer stakeholders to the resource adequacy modeling and program design (RAMPD) stakeholder initiative, and the importance of ensuring resources have a like-to-like resource adequacy (capacity) valuation to ensure fungibility within the RA market.^[16]

REV Renewables argued the reduction in QC will result in reduced reliability without access to the additional energy, as well as increased RA price pressures as further RA would need to be procured.^[17] A standard supply and demand analysis would suggest the reduction in RA supply will increase costs, however simultaneously the improved market modeling of the resources will lead to improved RA quality, and thus increased reliability of the QC on the system. Assuming no other changes in underlying conditions, this may ultimately lead to less demand for RA capacity in the long run, making the net effect on RA prices less clear.

DMM recommends access to energy in the extremes of the SOC should be available to the market in extenuating conditions. As proposed by REV Renewables, allowing access to the stored energy beyond the updated minimum and maximum continuous energy limits would require two modifications to Master File: (1) including a new maximum and minimum energy limit that extends beyond the range that is not power limited, but is still within the operating limits of the resource, and (2) a factor to adjust the Pmax of the resource to ensure power limits are not exceeded in the extended range.^[18]

DMM has previously recommended the ISO develop additional Master File parameters to address power limitations at the SOC extremes.^[19] To ensure there is consistent representation of the resource to the market, DMM recommends the ISO direct the LRAs to limit QC to the operational range that is not impacted by SOC limitations, and then allow resources to register their additional SOC and reduced power for extenuating circumstances if the market or system operators were to need the additional energy.

[1] Storage Design and Modeling Working Group on Outage Management, Uplift & DEB, and Mixed-Fuel & Distribution-Level Resources presentation, California ISO, November 12, 2025: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Nov12-2025.pdf

[2] Comments on Storage Design and Modeling Working Group Presentation on September 29, 2025, Department of Market Monitoring, October 14, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-sep-29-2025-working-group-presentation-oct-14-2025.pdf

[3] Comments on Storage Design and Modeling May 28, 2025 Presentation, Department of Market Monitoring, June 11, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-may-28-2025-presentation-jun-11-2025.pdf

[4] Ibid.

[5] Comments on Storage Design and Modeling Working Gr oup Presentation on June 30, 2025, Department of Market Monitoring, July 16, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-jun-30-2025-working-group-presentation-jul-16-2025.pdf

[6] Storage Design and Modeling Working Group, California ISO, November 14, 2025, p 56: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Nov12-2025.pdf

[7] Comments on Storage Design and Modeling Working Group Session 2 and 3, Department of Market Monitoring, March 7, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-working-group-sessions-2-and-3-mar-07-2025.pdf

[8] Comments on Storage Design and Modeling May 28, 2025 Presentation, Department of Market Monitoring, June 11, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-may-28-2025-presentation-jun-11-2025.pdf

[9] Comments on Storage BCR and DEBs July 8, 2024 Workshop, Department of Market Monitoring, July 18, 2024: https://www.caiso.com/documents/dmm-comments-on-storage-bcr-and-default-energy-bids-july-8-2024-workshop-jul-18-2024.pdf

[10] Comments on Storage Design and Modeling Working Group Presentation on August 14, 2025, Department of Market Monitoring, September 5, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-aug-14-2025-working-group-presentation-sep-05-2025.pdf

[11] Storage Design and Modeling Working Group on Outage Management, Uplift & DEB, and Mixed-Fuel & Distribution-Level Resources presentation, California ISO, November 12, 2025: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Nov12-2025.pdf

[12] DMM notes that the minimum and maximum continuous energy limit ought to be “best” represented to the market to not impact power limitations due to the SOC of the resource. The use of best acknowledges there are many temporary factors that can lead to power limitations of the storage resource, such as cell imbalance. The scheduling coordinator should work with their operator to have the long-term limitations accurately reflected to the market. Whereas short-term limitations, such as maintenance and cell imbalances, should not be reflected within the limitations. These limitations will then be incentivized through interrelated policies such as RAAIM or UCAP.

[13] Storage Design and Modeling Working Group on Outage Management, Uplift & DEB, and Mixed-Fuel & Distribution-Level Resources presentation, California ISO, November 12, 2025: https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Nov12-2025.pdf

[14] Comments on Storage Design and Modeling Issue Paper and Straw Proposal on Outage Management, Nonlinearity and SOC Clarification, Department of Market Monitoring, May 23, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-issue-paper-and-straw-proposal-on-outage-management-nonlinearity-and-soc-clarification-may-23-2025.pdf

[15] CAISO Storage Design and Modeling – Foldback/Non-Linearity Proposal, REV Renewables, November 12, 2025: https://stakeholdercenter.caiso.com/InitiativeDocuments/REV-Renewables-Presentation-Storage-Design-and-Modeling-Nov12-2025.pdf

[16] Comments on Resource Adequacy Modeling and Program Design Working Group, Department of Market Monitoring, March 13, 2025: https://www.caiso.com/documents/dmm-comments-on-resource-adequacy-modeling-and-program-design-working-group-mar-13-2025.pdf

[17] CAISO Storage Design and Modeling – Foldback/Non-Linearity Proposal, REV Renewables, November 12, 2025: https://stakeholdercenter.caiso.com/InitiativeDocuments/REV-Renewables-Presentation-Storage-Design-and-Modeling-Nov12-2025.pdf

[18] Ibid.

[19] Comments on Storage Design and Modeling Working Group Presentation on August 14, 2025, Department of Market Monitoring, September 5, 2025: https://www.caiso.com/documents/dmm-comments-on-storage-design-and-modeling-aug-14-2025-working-group-presentation-sep-05-2025.pdf

2. Provide your organization’s comments regarding the initiative’s overview and schedule.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

3. Provide your organization’s comments regarding the update on nonlinearity.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

4. Provide your organization’s comments regarding the presentation offered by REV Renewables.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

5. Provide your organization’s comments regarding the guiding principles related to the Uplift & Default Energy Bid (DEB) topic group.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

6. Provide your organization’s comments regarding the responses on Day-Ahead Uplift and Initial State-of-Charge (SOC) as part of the Uplift & Default Energy Bid (DEB) topic group.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

7. Provide your organization’s comments regarding Real-Time Uplift and Proposed Approaches as part of the Uplift & Default Energy Bid (DEB) topic group.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

8. Provide your organization’s comments regarding the notion of establishing a form of System SOC target or constraint, including your perspective on how the SOC target should be established and the relationship this target or constraint would have with market products.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

9. Provide your organization’s comments regarding the potential modifications to the storage DEB to enable the representation of real-time conditions and ease its use across different geographies.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

10. Provide your organization’s comments regarding the presentation offered by Pacific Gas & Electric (PG&E).

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

11. Provide your organization’s comments regarding the presentation offered by Vistra, including the discussion questions included in their materials.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

12. Provide your organization’s comments regarding the presentation offered by Cong Chen Ph.D., Assistant Professor, Thayer School of Engineering, Dartmouth College.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

13. Provide your organization’s comments regarding the update provided regarding the high sustainable limit (to ease the development of comments, please note that a more detailed review of the proposed guidance is included in the materials presented September 29, 2025).

https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

14. Provide your organization’s comments regarding the update and materials on outage reporting for distribution-level resources. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4)

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

15. Provide your organization’s comments regarding the materials and upcoming discussion on the co-located variable energy resource Follow DOT topic. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

16. Provide your organization’s comments regarding the upcoming discussion on mixed-fuel ancillary services. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

17. Please provide any additional comments, feedback, or examples in the Nov 12 stakeholder meeting. You may upload examples or data using the Attachments field below.

Please see the PDF attached below the final question for DMM's fully formatted complete set of comments. For the reader's convenience, the complete text of the comments is pasted in response to #1, but there may be some formatting errors.

1. Please provide a summary of your organization's general comments on the materials shared and subsequent discussion during the Nov 12 meeting.

PG&E’s Primary Comments

• Implementation Timeline: Strongly supports CAISO’s plan to reserve bandwidth in Q3 2027 for enhancements identified in this initiative. The timeline is realistic given the complexity of DAME and EDAM implementation and the significant enhancements expected after go-live.
• State Of Charge: Endorses CAISO’s current SOC range approach and emphasizes adding SOC max and SOC min parameters to improve visibility under stressed conditions. Maintaining the minimum SOC constraint is essential to ensure reliable discharge capability and simplify battery operations.
• Day-Ahead Uplift: Recommends delaying any decision to discontinue Day-Ahead BCR until at least six months after DAME go-live to confirm whether uplift remains necessary under the new market design.
• Default Energy Bids (DEB): Calls for a comprehensive review of current DEB calculation methods to ensure they accurately reflect true opportunity costs. This analysis should address forecast accuracy, buyback cost treatment, multi-day cycling patterns, and the ability of batteries to provide services beyond energy.

Additional Comments

• Supports consideration of AS re-optimization as a major market initiative after the successful implementation of DAME and EDAM.
• Could support implementing REV Renewables’ proposal if CAISO confirms minimal resource impact and feasibility.
• Agrees with CAISO’s clarification on why High Sustainable Limits (HSL) values are not auto-generated, recognizing resource flexibility and calculation complexity.
• Provides detailed responses to Vistra’s questions regarding SOC management, physical constraints, and market horizon feasibility.
• Requests a clearer definition of system SOC and its practical application.

2. Provide your organization’s comments regarding the initiative’s overview and schedule.

PG&E strongly supports CAISO’s proposed reserving implementation bandwidth for Q3 2027 for any enhancements identified in this initiative. The timeline is realistic given the complexity of DAME and EDAM implementation and the significant enhancements expected after go-live.

3. Provide your organization’s comments regarding the update on nonlinearity.

• PG&E supports CAISO’s current approach of requiring SOC ranges that allow discharge at the RA maximum value until changes—such as those proposed by REV Renewables—are incorporated into the NGR model to enable dispatch within foldback ranges.  REV’s proposal may offer a path to relaxing this restriction in the near term.

• CAISO should prioritize implementing additional SOC range parameters (SOC max and SOC min) so that the physical minimum SOC is visible to operators under extremely stressed conditions for exceptional dispatch. While CAISO could consider relaxing its constraint on the maximum SOC range—since battery operators can constrain bids to avoid full charge awards when nearing maximum SOC in real time—maintaining the minimum SOC constraint remains essential. This guarantees discharge awards and simplifies operator management of batteries under stressed conditions. 

4. Provide your organization’s comments regarding the presentation offered by REV Renewables.

PG&E could support an initiative to implement REV Renewables’ proposed solution if CAISO agreed that it would require relatively minimal internal resources. The proposal enables market dispatch of batteries with foldback ranges, based on Master File-registered foldback range values and by adding constraints within the real-time NGR optimization.  This would have the benefit of giving CAISO access to feasible dispatches of batteries in the foldback range without requiring batteries to submit derates, improving both market efficiency and potential storage utilization, and eliminating the risk of RAAIM penalties for batteries offering their foldback range. These changes appear to not introduce new decision variables — particularly integer variables— so they should not negatively impact solution time or convergence. 

Successful implementation would depend on market participant (i.e., battery operators) acceptance of this approach as a near-term solution to the foldback issue and requires updates to the Master File (which CAISO has indicated it is receptive to making, allowing both RA continuous energy limits and physical continuous energy limits of batteries visible to operators) along with seemingly straightforward model changes, such as additional charge and discharge constraints.

5. Provide your organization’s comments regarding the guiding principles related to the Uplift & Default Energy Bid (DEB) topic group.

No comment.  

6. Provide your organization’s comments regarding the responses on Day-Ahead Uplift and Initial State-of-Charge (SOC) as part of the Uplift & Default Energy Bid (DEB) topic group.

PG&E recommends postponing any decision to discontinue Day-Ahead BCR until at least six months after DAME go-live. While CAISO’s analysis of Day-Ahead Uplift makes a strong case for eliminating day ahead BCR under the current market regime, the implementation of imbalance reserve and reliability capacity products in the DAME initiative could change this assessment or the need for uplift.

7. Provide your organization’s comments regarding Real-Time Uplift and Proposed Approaches as part of the Uplift & Default Energy Bid (DEB) topic group.

 No comment.  

8. Provide your organization’s comments regarding the notion of establishing a form of System SOC target or constraint, including your perspective on how the SOC target should be established and the relationship this target or constraint would have with market products.

PG&E cannot support or oppose this proposal without a clearer definition of system SOC and its practical application. Specifically, PG&E needs clarity on what system SOC means, how its minimum and maximum limits are determined, and how it can be effectively employed to manage the portfolio of storage in CAISO. 

9. Provide your organization’s comments regarding the potential modifications to the storage DEB to enable the representation of real-time conditions and ease its use across different geographies.

PG&E request thorough analysis of whether current methods for calculating real-time and day-ahead battery DEBs accurately identify the true opportunity cost. Specifically, does the “fourth highest hour” approach correctly capture a battery’s real opportunity cost in these markets? If not, PG&E suggests examining potential causes, including:

1. use of a forecasted price that is significantly different from the actual fourth highest price  
2. Incorrect inclusion of costs of day ahead buyback in the opportunity cost calculation?
3. Errors from using an energy-only calculation when batteries can offer other services in addition to energy (especially relevant post-DAME go-live)
4. Lack of consideration for multi-day values or nonstandard cycling patterns beyond a single-cycle pattern. 

PG&E requests this analysis at both the portfolio and individual battery level, with the latter analysis appropriately anonymized to protect commercial strategies. 

10. Provide your organization’s comments regarding the presentation offered by Pacific Gas & Electric (PG&E).

PG&E supports consideration of AS re-optimization as a major market initiative after the successful implementation of DAME and EDAM. However, PG&E emphasizes that this effort requires a comprehensive stakeholder process that extends to all market participants — not only those involved in the storage enhancements discussions. 

11. Provide your organization’s comments regarding the presentation offered by Vistra, including the discussion questions included in their materials.

PG&E provides the following positions on Vistra’s questions:

1. Who should be responsible for managing the storage’s SOC – SC or ISO?

• Batteries should manage their own SOC, provided CAISO has sufficient confidence —on an aggregate basis — in the deliverability of battery energy awarded in the markets or dispatched by CAISO. 
• The CAISO’s RA framework (distinct from the PUC’s related RA framework) could help secure energy guarantees on a planning basis, potentially through “slice of day” submission to indicate storage commitments by batteries.
• Currently, day-ahead bid-in SOC is managed by SCs, while real-time SOC is managed primarily by CAISO over a myopic horizon.  One option for longer-term real time planning would be constraining end-of-horizon or/and binding dispatches to ensure the feasibility of day-ahead awards, similar to energy-limited hydro.

2. Is allowing market enforcing physical parameters similar to the physical constraints of other assets (Pmin,Pmax)?
   • Battery operators appear to want CAISO to manage assets subject to real physical constraints estimated based on telemetry, as evidenced by the time spent on the foldback issue. If this is not the case, as Vistra suggests, battery operators should weigh in to indicate this.
   • If battery operators want CAISO to enforce SOC parameters, they must accept the current market model. 
   • Vistra’s assertion that batteries should have the option to manage their own SOCs independently should be addressed by CASIO with legal and tariff clarity.

12. Provide your organization’s comments regarding the presentation offered by Cong Chen Ph.D., Assistant Professor, Thayer School of Engineering, Dartmouth College.

 No comment.  

13. Provide your organization’s comments regarding the update provided regarding the high sustainable limit (to ease the development of comments, please note that a more detailed review of the proposed guidance is included in the materials presented September 29, 2025).

https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

PG&E agrees with CAISO’s clarification on why it does not automatically generate (High Sustainable Limit) HSL values for resources. While CAISO recommends a calculation method, resources may choose alternative approaches, and CAISO cannot unilaterally calculate HSL because other factors beyond those in the recommended formula may influence the value.

14. Provide your organization’s comments regarding the update and materials on outage reporting for distribution-level resources. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4)

 No comment.  

15. Provide your organization’s comments regarding the materials and upcoming discussion on the co-located variable energy resource Follow DOT topic. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

 No comment.  

16. Provide your organization’s comments regarding the upcoming discussion on mixed-fuel ancillary services. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

 No comment.  

17. Please provide any additional comments, feedback, or examples in the Nov 12 stakeholder meeting. You may upload examples or data using the Attachments field below.

 No comment.  

1. Please provide a summary of your organization's general comments on the materials shared and subsequent discussion during the Nov 12 meeting.

PGE appreciates the breadth of topics covered on Nov. 12 and sees the nonlinearity/foldback problem statement as an impactful near-term enhancement opportunity. The CAISO’s proposed exclusion of the lower and upper foldback regions could improve operational certainty but would understate resource-specific physical capability. PGE supports continued evaluation of approaches that improve upon the status quo while preserving the flexibility to optimize the entire range of a storage resource’s physical capacity.

Other topics, including SOC responsibility, uplift/DEB, and real-time AS enforcement, are important but not yet conceptually mature in the stakeholder community, and the learning process is still unfolding. Nonetheless, clarifying SOC roles, improving constraint transparency, and ensuring region-neutral DEB structures will support consistent storage behavior across the regional footprint. PGE will remain engaged in these upcoming discussions.

2. Provide your organization’s comments regarding the initiative’s overview and schedule.

3. Provide your organization’s comments regarding the update on nonlinearity.

PGE views the nonlinearity update as a pivotal issue for SDM.

The CAISO’s proposed exclusion of the foldback region improves operations but inherently removes physically available energy from the modeled envelope. This approach is tightly linked to CPUC QC requirements for RA and may be overly conservative for a multi-BAA environment.

From a WEIM/EDAM participant perspective, operational modeling should reflect actual physical capability rather than CPUC RA-driven simplifications, especially as storage technologies and performance curves vary across BAAs. Eliminating the foldback region entirely reduces modeled flexibility footprint-wide and could unnecessarily constrict capacity during tight conditions.

Further, while PGE understands that the CAISO has verbally characterized the foldback proposal as a temporary solution, without a stated timeframe, PGE is concerned that this temporary measure could persist longer than intended.

PGE prefers an approach which accurately represents reduced power near SOC limits, rather than discarding that range. Such a design better aligns with EDAM scalability, regional neutrality, and market efficiency.

4. Provide your organization’s comments regarding the presentation offered by REV Renewables.

PGE appreciates the REV proposal and sees value in representing nonlinearity through capability-based constraints rather than eliminating the foldback region entirely. As an enhancement to REV’s approach, PGE proposes evaluating a SOC-percentage formulation instead of fixed MWh thresholds.

Using SOC% to define foldback start points would better accommodate normal variations in available energy and dynamic Pmax (such as module outages, inverter derates, and ambient-driven performance changes) without requiring frequent updates to absolute MWh values. A SOC%-based structure scales naturally with changing conditions, while retaining the simplicity of the REV proposal. PGE is open to further exploration of this conceptual refinement with CAISO staff and regional stakeholders.

PGE believes that the REV proposal would allow the market to reflect physical capability more accurately across external BAAs without introducing complexity into the CAISO’s market model. As presented, PGE is directionally supportive of, and preferential towards, the REV proposal.

5. Provide your organization’s comments regarding the guiding principles related to the Uplift & Default Energy Bid (DEB) topic group.

6. Provide your organization’s comments regarding the responses on Day-Ahead Uplift and Initial State-of-Charge (SOC) as part of the Uplift & Default Energy Bid (DEB) topic group.

7. Provide your organization’s comments regarding Real-Time Uplift and Proposed Approaches as part of the Uplift & Default Energy Bid (DEB) topic group.

8. Provide your organization’s comments regarding the notion of establishing a form of System SOC target or constraint, including your perspective on how the SOC target should be established and the relationship this target or constraint would have with market products.

9. Provide your organization’s comments regarding the potential modifications to the storage DEB to enable the representation of real-time conditions and ease its use across different geographies.

PGE supports continued refinement of the storage DEB to improve representation of intertemporal opportunity cost and real-time system conditions. At the same time, DEB structures should remain broadly applicable across EDAM BAAs and avoid relying on California-specific assumptions. A balanced, region-neutral approach will help ensure consistent and efficient storage participation across the footprint.

10. Provide your organization’s comments regarding the presentation offered by Pacific Gas & Electric (PG&E).

11. Provide your organization’s comments regarding the presentation offered by Vistra, including the discussion questions included in their materials.

12. Provide your organization’s comments regarding the presentation offered by Cong Chen Ph.D., Assistant Professor, Thayer School of Engineering, Dartmouth College.

13. Provide your organization’s comments regarding the update provided regarding the high sustainable limit (to ease the development of comments, please note that a more detailed review of the proposed guidance is included in the materials presented September 29, 2025).

https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

14. Provide your organization’s comments regarding the update and materials on outage reporting for distribution-level resources. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4)

15. Provide your organization’s comments regarding the materials and upcoming discussion on the co-located variable energy resource Follow DOT topic. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

16. Provide your organization’s comments regarding the upcoming discussion on mixed-fuel ancillary services. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

17. Please provide any additional comments, feedback, or examples in the Nov 12 stakeholder meeting. You may upload examples or data using the Attachments field below.

1. Please provide a summary of your organization's general comments on the materials shared and subsequent discussion during the Nov 12 meeting.

REV Renewables (REV) appreciates CAISO continuing discussions on this important initiative with its all-day meeting and allowing stakeholders to present proposals. As discussed in #3, REV is concerned with CAISO’s proposed near-term approach to address nonlinearity as it would negatively impact reliability, ratepayers, and storage owners by limiting energy available in the market. REV encourages further consideration of a solution, such as REV’s alternate proposal, to integrate nonlinearity into the market model in the near term to avoid these negative impacts. CAISO should aim to implement such a model solution for the Fall 2026 release given that this is also critical for EDAM storage resource integration.

2. Provide your organization’s comments regarding the initiative’s overview and schedule.

REV is encouraged to see the schedule for most of the initiative coming to decision in 2026. However, given that the initiative has been in progress for nearly a year and is only at the straw proposal phase for a few parts and near the issue paper stage for others, while some issues have not even been discussed (e.g. Track 3), it is clear that more substantive work needs to be done in the next quarter to achieve this schedule.

3. Provide your organization’s comments regarding the update on nonlinearity.

REV strongly opposes CAISO’s proposed solution for resources to only reflect the range unaffected by foldback Min/Max Continuous Energy Limit in the ISO’s Master File. CAISO’s proposal would cut 5-15% of storage energy available to sell in the market, leading to potential reliability impacts in the event of emergency where it’s needed, as well as significant lost revenue for storage owners. This lost energy will also be a loss for consumers with impact on cost of storage and potentially market prices as less energy is available. Additionally, the proposed limitation is discriminatory towards storage given that other resources have their physical restrictions integrated into the market model, such as ramp rates for thermal resources. This also infringes on a storage operators right per FERC Order 841 to self-manage their SOC through the participation model.

CAISO has two stated reasons for this proposal: 1) to ensure compliance with CPUC Qualifying Capacity Resource Adequacy (RA) definition of needing 4 hours of max continuous energy unaffected by foldback; and 2) CAISO Operations is increasingly concerned with infeasible dispatches and deviations due to foldback.

• REV agrees on CPUC Resource Adequacy definition (reason #1), but as stated in our presentation this could be done with something like a “RA Max/Min Continuous Energy Limit” field in the Master File if needed. This new field would not be used in the market model. CAISO does not need to impact operational parameters to support compliance with CPUC RA. Additionally, implementing an operational restriction for CPUC compliance purposes could be discriminatory against EIM/EDAM entities with storage that do not need to comply with CPUC. An RA specific limit field would allow EIM/EDAM entities the option to use that field for their RA purposes or not.
• REV does not agree that CAISO should make changes to the operational parameters in the CAISO market for foldback impacts. As discussed above, the proposed operational limitation is negative for reliability, consumers, and storage operators, and is discriminatory towards storage. REV understands that CAISO proposes this as an interim solution until the Track 3 “biddable SOC” model is implemented. However, if the schedule stays on track, that would mean waiting until mid-2027 decision and sometime after that for implementation (likely 2028 at best). This timeline would leave storage with restricted MWh for ~3 years, which is unacceptable.
  • Additionally, if the solution would only be integrated into the new, yet-to-be-defined SOC model, then that would make the Non-Generator Resource (NGR) model obsolete. REV only supports future storage model development if the NGR model is also continued. The NGR model works very well for storage, with a few exceptions such as nonlinearity. Any new model takes time to implement and work out issues. Given this uncertainty, CAISO should not rely on a new model to fix this nonlinearity issue.

CAISO showed several bar charts to suggest that most assets already represent only the range unaffected by foldback. REV requests more information on how this data was calculated, such as what fields or operational values were used in the calculation and whether the resource was actually dispatched in the foldback range to reach the stated values. Additionally, while the data show that the discharge range may be already limited by storage operators, the charging range is not and limiting this range could negatively impact a storage resource’s ability to fully charge and offer its full RA capability to the grid.

To be clear, REV is very supportive of addressing the nonlinearity issue. In fact, REV raised this issue with CAISO and in stakeholder forums since 2020. However, the proposed near-term solution is not the answer.

4. Provide your organization’s comments regarding the presentation offered by REV Renewables.

REV appreciates the opportunity to present our solution to account for foldback in the market model. This would limit infeasible dispatches and allow the high/low ends of state of charge to be accessed (fixing CAISO’s reason #2 as discussed above).

REV chose a linear representation a way to very closely mirror nonlinearity because it assumed it would be easier to implement. However, if CAISO prefers nonlinear model and that has a similar implementation timeline, REV is open to this and other adjustments to this proposal. One item that is important is the ability to update nonlinearity limits in the Real Time. These updates may be done easier if the limits are represented as a percentage rather than a MWh level. Again, these are details that could be discussed in the stakeholder forum with CAISO as we understand what model improvements are possible in the near-term.

REV requests CAISO provide an update on the feasibility of REV’s or a similar solution to integrate into the market model, including an implementation timeline. If such a solution can be done in the Fall 2026 release, REV suggests that no other interim solution (e.g. continuous energy limits or outage cards) is necessary.

5. Provide your organization’s comments regarding the guiding principles related to the Uplift & Default Energy Bid (DEB) topic group.

REV supports the guiding principles related to uplift and DEB. REV agrees if the storage operator actions led to inefficient dispatch it should not be allowed for uplift, while inefficient dispatch due to the market model should be allowed for uplift.

6. Provide your organization’s comments regarding the responses on Day-Ahead Uplift and Initial State-of-Charge (SOC) as part of the Uplift & Default Energy Bid (DEB) topic group.

REV continues to support keeping Day-Ahead uplift eligibility, particularly until EDAM and its related new products, such as imbalance reserves, is rolled out and CAISO and participants are able to understand its impact. While REV agrees Day-Ahead uplift will likely be minimal, it should not be eliminated right before these significant market changes.

7. Provide your organization’s comments regarding Real-Time Uplift and Proposed Approaches as part of the Uplift & Default Energy Bid (DEB) topic group.

REV continues to encourage Real-Time DEB adjustments that can better reflect changing real-time constraints and opportunity costs. Locking in the DEB to day-ahead prices is not reflective of real-time conditions, such as transmission constraints or outages that can lead to mitigation and often results in inefficient storage dispatch.

8. Provide your organization’s comments regarding the notion of establishing a form of System SOC target or constraint, including your perspective on how the SOC target should be established and the relationship this target or constraint would have with market products.

 REV defers comment on this issue at this time.

9. Provide your organization’s comments regarding the potential modifications to the storage DEB to enable the representation of real-time conditions and ease its use across different geographies.

 As discussed in #7, REV supports modifications to the real-time DEB to better reflect real-time conditions, which are often location specific.

10. Provide your organization’s comments regarding the presentation offered by Pacific Gas & Electric (PG&E).

REV supports PG&E’s proposed enhancements of CAISO AS reoptimization. REV agrees with the benefits laid out and that this solution would improve real time market efficiency and reduce the need for bid cost recovery. REV encourages further discussion of this proposal, though understands it may be more of a mid-term solution.

11. Provide your organization’s comments regarding the presentation offered by Vistra, including the discussion questions included in their materials.

REV appreciates Vistra’s proposal and agrees with the importance of storage resources being able to self-manage their SOC. REV encourages CAISO to provide more time for group discussion in a workshop on the questions posted by Vistra, as they are important foundational positions for being able to move forward other issues including DEB and uplift as well as nonlinearity. 

12. Provide your organization’s comments regarding the presentation offered by Cong Chen Ph.D., Assistant Professor, Thayer School of Engineering, Dartmouth College.

  REV defers comments on this issue at this time.

13. Provide your organization’s comments regarding the update provided regarding the high sustainable limit (to ease the development of comments, please note that a more detailed review of the proposed guidance is included in the materials presented September 29, 2025).

https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

  REV defers comments on this issue at this time.

14. Provide your organization’s comments regarding the update and materials on outage reporting for distribution-level resources. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4)

  REV defers comments on this issue at this time.

15. Provide your organization’s comments regarding the materials and upcoming discussion on the co-located variable energy resource Follow DOT topic. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

  REV defers comments on this issue at this time.

16. Provide your organization’s comments regarding the upcoming discussion on mixed-fuel ancillary services. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

  REV defers comments on this issue at this time.

17. Please provide any additional comments, feedback, or examples in the Nov 12 stakeholder meeting. You may upload examples or data using the Attachments field below.

  REV has no further comments at this time.

1. Please provide a summary of your organization's general comments on the materials shared and subsequent discussion during the Nov 12 meeting.

San Diego Gas and Electric (SDG&E) appreciates the opportunity to comment on the November 12 working group meeting for the Storage design and modeling (SDM) initiative. Our comments below focus primarily on feedback relating to nonlinearity, including the proposal from REV Renewable, as well as the uplift and initial/target SOC topics. 

2. Provide your organization’s comments regarding the initiative’s overview and schedule.

SDG&E thanks CAISO for the update and supports the initiative overview and schedule as described on pages 6-8 of the presentation. SDG&E strongly supports prioritization of this initiative in the roadmap and encourages CAISO to consider what (if any) near-term improvements to either improve the model or facilitate operational efficiencies, can be made in advance of the 2027 implementation timeline. 

3. Provide your organization’s comments regarding the update on nonlinearity.

SDG&E cautions that CAISO’s proposed revised approach of using Master File continuous energy limits to exclude SOC ranges affected by foldback could create unintended consequences for system reliability and market efficiency. This approach reduces the operational capacity available to the system, results in physical withholding of energy, and increases energy and ancillary services prices. By embedding RA logic into resource operations, CAISO risks driving overbuild requirements for storage assets to meet compliance with constrained SOC representation, rather than leveraging their full market design capability. The proposed revised approach presented by CAISO during the working group meeting does not address these underlying issues. While SDG&E recognizes this revision is driven by CAISO’s desire to move swiftly to a consistent representation of these ranges for the purpose of preventing infeasible dispatches during operations, the cons of preventing the market from accessing available energy should point to an alternative short-term solution. 

Further, SDG&E requests CAISO commit to developing and implementing a more durable solution as quickly as possible. It has been made clear in both CAISO’s analysis and stakeholder comments that addressing nonlinearity for storage resources is complicated by resource constraints, limitations of the market model, and alignment with the RA paradigm. However, it is critical to implement a proposal on nonlinearity that accomplishes the goals of improving market efficiency, reliability, and avoiding undue costs to ratepayers from reducing the available capacity of storage assets.  

4. Provide your organization’s comments regarding the presentation offered by REV Renewables.

SDG&E agrees with REV’s assertion that CPUC RA QC validation rules should not influence operational limits within CAISO’s market design, as these are distinct frameworks and should remain separate. Based on our initial review, REV’s proposed approach would be a preferred alternative to CAISO’s revised proposal, as it appears to keep the RA and operational parameters separate while addressing the operational impacts of nonlinearity in the market dispatch. As part of the next set of meeting materials for the SDM initiative, SDG&E requests that CAISO provide an evaluation of the implementation effort and resources required for this proposal to inform stakeholder feedback and prioritization of this approach. 

5. Provide your organization’s comments regarding the guiding principles related to the Uplift & Default Energy Bid (DEB) topic group.

SDG&E supports CAISO’s guiding principles and thank CAISO for their responsiveness to stakeholder feedback, as the principles are reflective of the challenges described by stakeholders on this topic. 

6. Provide your organization’s comments regarding the responses on Day-Ahead Uplift and Initial State-of-Charge (SOC) as part of the Uplift & Default Energy Bid (DEB) topic group.

Regarding initial SOC, SDG&E supports exploring methods to improve accuracy by either refining default SOC values or incentivizing SCs to provide accurate SOC information within reasonable thresholds. These requirements should remain forward-looking and account for evolving market features—such as imbalance reserves and storage envelope equations—that could make current accuracy thresholds impractical in the future. At this point, SDG&E does not take a position on tying SOC accuracy to uplift eligibility due to the challenges outlined by stakeholders regarding real-time SOC management (i.e., exceptional dispatch, market power mitigation, etc…), but we are supportive of further discussion on this topic. 

7. Provide your organization’s comments regarding Real-Time Uplift and Proposed Approaches as part of the Uplift & Default Energy Bid (DEB) topic group.

SDG&E supports CAISO’s guiding principle that real-time uplift should apply only to negative revenues caused by ISO actions or market algorithms, not to outcomes driven by resource bidding behavior. DMM’s analysis shows that OOM dispatch, while seemingly infrequent when compared against every hour of the day, is concentrated around early morning and early evening net peak hours - periods of heightened system stress where uneconomic outcomes can have significant reliability and cost implications. Because of this, OOM dispatch due to MIO remains an important consideration in the real-time uplift framework. 

Additionally, while charging mitigation appears to occur infrequently, its magnitude can be substantial. When mitigated bids prevent resources from charging to meet future obligations, the resulting shortfalls can create severe operational challenges and undermine market efficiency. SDG&E believes any real-time uplift design must account for these potentially high-impact scenarios to ensure resources are not penalized for conditions beyond their control. 

8. Provide your organization’s comments regarding the notion of establishing a form of System SOC target or constraint, including your perspective on how the SOC target should be established and the relationship this target or constraint would have with market products.

SDG&E does not have a position at this time on establishing a form of System SOC target or constraint as we still do not fully understand the proposal. CAISO asserts that a system SOC concept would align with existing stakeholder proposals on initial SOC submission, and therefore the ability to qualify for make-whole payments under certain proposed uplift frameworks. While inclusion of an SOC submission requirement may be fairly straightforward, the proposal lacks the detail required for stakeholders to make any such assessments. It is unclear to SDG&E what how this target/constraint would be submitted and how it would impact system SOC visibility. SDG&E requests further information and clarification on this topic. 

9. Provide your organization’s comments regarding the potential modifications to the storage DEB to enable the representation of real-time conditions and ease its use across different geographies.

No comment. 

10. Provide your organization’s comments regarding the presentation offered by Pacific Gas & Electric (PG&E).

SDG&E appreciates PG&E’s proposal to reform ancillary services optimization as a strategic enhancement to CAISO’s market design. Providing resources the ability to buy back day-ahead AS awards through decremental bidding could improve operational flexibility and reduce uneconomic outcomes caused by rigid constraints. This approach has the potential to minimize OOM dispatch and better align real-time decisions with system needs, particularly as storage penetration grows. 

The integration of immense quantities of variable energy resources and energy storage systems suggests that we have significant opportunities to re-optimize existing products, which could yield meaningful improvements to economic outcomes and dispatch efficiency throughout the market. However, SDG&E understands real-time AS re-optimization to be a very large, longer-term project. As such, SDG&E recommends this be considered later in this initiative, after near-term priorities and incremental fixes are addressed. 

11. Provide your organization’s comments regarding the presentation offered by Vistra, including the discussion questions included in their materials.

Vistra’s proposal to allow self-management through unmitigated bidding, paired with non-performance penalties and the elimination of uplift payments, represents a significant departure from current design. This concept introduces complex questions around market power mitigation, risk allocation, and compliance. These issues would require careful analysis and discussion to understand and weigh the risks of any unintended consequences, such as impacts on reliability or inequitable cost shifts. Given the breadth of items in scope already, along with CAISO’s and stakeholder’s resource constraints, we recommend prioritizing other topics in the SDM initiative—such as uplift redesign, DEB redesign, and SOC accuracy measures—that can deliver immediate benefits to storage resources and scheduling coordinators. 

12. Provide your organization’s comments regarding the presentation offered by Cong Chen Ph.D., Assistant Professor, Thayer School of Engineering, Dartmouth College.

No comment. 

13. Provide your organization’s comments regarding the update provided regarding the high sustainable limit (to ease the development of comments, please note that a more detailed review of the proposed guidance is included in the materials presented September 29, 2025).

https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

SDG&E appreciates the discussion on this topic and looks forward to further clarification regarding the iHSL calculation and methodology, as well as any requirements on its submission, in the upcoming SDM paper. 

14. Provide your organization’s comments regarding the update and materials on outage reporting for distribution-level resources. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4)

No comment.

15. Provide your organization’s comments regarding the materials and upcoming discussion on the co-located variable energy resource Follow DOT topic. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

No comment.

16. Provide your organization’s comments regarding the upcoming discussion on mixed-fuel ancillary services. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

No comment.

17. Please provide any additional comments, feedback, or examples in the Nov 12 stakeholder meeting. You may upload examples or data using the Attachments field below.

No comment.

1. Please provide a summary of your organization's general comments on the materials shared and subsequent discussion during the Nov 12 meeting.

Please see attached file.

2. Provide your organization’s comments regarding the initiative’s overview and schedule.

3. Provide your organization’s comments regarding the update on nonlinearity.

4. Provide your organization’s comments regarding the presentation offered by REV Renewables.

5. Provide your organization’s comments regarding the guiding principles related to the Uplift & Default Energy Bid (DEB) topic group.

6. Provide your organization’s comments regarding the responses on Day-Ahead Uplift and Initial State-of-Charge (SOC) as part of the Uplift & Default Energy Bid (DEB) topic group.

7. Provide your organization’s comments regarding Real-Time Uplift and Proposed Approaches as part of the Uplift & Default Energy Bid (DEB) topic group.

8. Provide your organization’s comments regarding the notion of establishing a form of System SOC target or constraint, including your perspective on how the SOC target should be established and the relationship this target or constraint would have with market products.

9. Provide your organization’s comments regarding the potential modifications to the storage DEB to enable the representation of real-time conditions and ease its use across different geographies.

10. Provide your organization’s comments regarding the presentation offered by Pacific Gas & Electric (PG&E).

11. Provide your organization’s comments regarding the presentation offered by Vistra, including the discussion questions included in their materials.

12. Provide your organization’s comments regarding the presentation offered by Cong Chen Ph.D., Assistant Professor, Thayer School of Engineering, Dartmouth College.

13. Provide your organization’s comments regarding the update provided regarding the high sustainable limit (to ease the development of comments, please note that a more detailed review of the proposed guidance is included in the materials presented September 29, 2025).

https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

14. Provide your organization’s comments regarding the update and materials on outage reporting for distribution-level resources. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4)

15. Provide your organization’s comments regarding the materials and upcoming discussion on the co-located variable energy resource Follow DOT topic. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

16. Provide your organization’s comments regarding the upcoming discussion on mixed-fuel ancillary services. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

17. Please provide any additional comments, feedback, or examples in the Nov 12 stakeholder meeting. You may upload examples or data using the Attachments field below.

1. Please provide a summary of your organization's general comments on the materials shared and subsequent discussion during the Nov 12 meeting.

2. Provide your organization’s comments regarding the initiative’s overview and schedule.

3. Provide your organization’s comments regarding the update on nonlinearity.

4. Provide your organization’s comments regarding the presentation offered by REV Renewables.

5. Provide your organization’s comments regarding the guiding principles related to the Uplift & Default Energy Bid (DEB) topic group.

6. Provide your organization’s comments regarding the responses on Day-Ahead Uplift and Initial State-of-Charge (SOC) as part of the Uplift & Default Energy Bid (DEB) topic group.

7. Provide your organization’s comments regarding Real-Time Uplift and Proposed Approaches as part of the Uplift & Default Energy Bid (DEB) topic group.

8. Provide your organization’s comments regarding the notion of establishing a form of System SOC target or constraint, including your perspective on how the SOC target should be established and the relationship this target or constraint would have with market products.

9. Provide your organization’s comments regarding the potential modifications to the storage DEB to enable the representation of real-time conditions and ease its use across different geographies.

10. Provide your organization’s comments regarding the presentation offered by Pacific Gas & Electric (PG&E).

11. Provide your organization’s comments regarding the presentation offered by Vistra, including the discussion questions included in their materials.

12. Provide your organization’s comments regarding the presentation offered by Cong Chen Ph.D., Assistant Professor, Thayer School of Engineering, Dartmouth College.

13. Provide your organization’s comments regarding the update provided regarding the high sustainable limit (to ease the development of comments, please note that a more detailed review of the proposed guidance is included in the materials presented September 29, 2025).

https://stakeholdercenter.caiso.com/InitiativeDocuments/Presentation-Storage-Design-and-Modeling-Sep-29-2025.pdf

14. Provide your organization’s comments regarding the update and materials on outage reporting for distribution-level resources. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4)

15. Provide your organization’s comments regarding the materials and upcoming discussion on the co-located variable energy resource Follow DOT topic. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

16. Provide your organization’s comments regarding the upcoming discussion on mixed-fuel ancillary services. This topic will be discussed during the next stakeholder meeting (scheduled for Dec. 4).

17. Please provide any additional comments, feedback, or examples in the Nov 12 stakeholder meeting. You may upload examples or data using the Attachments field below.