February 4, 2026

On January 23, 2026, ISO-NE issued a request for feedback on the Resource Accreditation Modeling Impact Analysis (IA) it plans to conduct. ISO-NE sought feedback targeted at helping ISO understand stakeholder views on the output metrics and input assumptions. NESCOE submitted the following response via ISO-NE’s online feedback form on February 4, 2026.

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NESCOE Cover Email

We are interested in understanding and identifying what the most material drivers of costs are.  We need to understand the design changes that are most likely to impact consumer costs as we will focus our attention and possible amendments on these critical cost drivers. We understand that many of the inputs/assumptions have a range of reasonableness and need to understand for the drivers that materially increase costs where they sit within this range.  We believe this will help with a healthy debate on tradeoffs between risks and consumer costs.

We completed the survey based on our current understanding of the proposal but as we went through, we realized we still aren’t always able to fit the pieces together to understand what assumptions would be most helpful in answering our overarching questions. Our key questions are below. If the detailed responses we put into the survey aren’t the best way to get at answers to these questions, we’d welcome the opportunity to talk with you and find a better way to get at the answers we’re looking for. Ultimately understanding these questions big picture is more important than the specifics of what we put into the survey:

• What are the key price drivers?
• What changes can be made to these drivers and what risks are increased if so.
• What design changes are adding the most cost?
• What would happen if more perfect capacity came online (assuming no retirements), how would that impact the accreditation of constrained resources?
• There were no questions that went toward understanding changes in the demand curves. We’d like to understand what drives the demand curves?
• We are still seeking to better understand the EUE calculation that identifies scarcity events and how it impacts resources, particularly storage. What drives the number of hours at criteria – for example, what would the impact of 6 scarcity hours vs 8 be in determining resources accreditation value and associated consumer capacity costs?
• What cost increases are expected from the application of the gas constraint demand curve? This includes a need for in-depth analysis to determine if these units would become the marginal clearing unit in the winter season and at what price would be needed for units to make firm fuel arrangements.  Additional questions include:
  • Would there be a benefit to consumers from either adding a third season or extending the summer season such that the gas constraint only applies in the months where it actually exists (3 winter months versus applying it to all 6 months as the winter seasons is currently defined)?
  • We’d like to understand any cost savings or differences between the two gas constraint approaches – accreditation approach versus gas constraint demand curve – to determine which may be more beneficial to consumers.

ISO-NE Feedback Form

Part A: Resource Accreditation Modeling IA CCP19 Base Case and Analysis

1. Name and Organization
2. Additional Analysis Explaining Results of the Near-Term Base Case:
   ISO already plans to deliver a heat map of expected unserved energy (EUE) hours by month and hour, how representative resource’s storage duration impacts its seasonal rMRI, system MRI curves and demand curves, and information on the distribution of reliability events by season. What potential additional analysis would be of greatest interest to you for the near-term base case? Please rank these selections in the order of your preference.

3. Impact of Various Design Elements:
   What impacts of changing the modeling assumptions or design elements would you be most interested in seeing results for among those listed below? These options focus on changes that may be feasible to model. Please rank these selections in the order of your preference.

4. For the base case, which risk split of the loss of load expectation (LOLE) would be most interesting to see a sensitivity on:
   Note, the ISO design currently proposes 50/50 summer/winter. Select one of the following:

• 80/20 summer/ winter
• 70/30 summer/ winter
• 60/40 summer/winter

5. From the questions above, which type of analysis is of greatest interest to you? Select one of the following.

• Further analyzing key results (question 2)
• Evaluating the impacts on outcomes to design changes (question 3)
• Evaluating the impact of a different risk split (question 4)

Part B: Resource Accreditation Modeling IA Future Base Case and Scenarios

Consistent with stakeholder input, the ISO is planning to run a future base case that provides similar information to the CCP 19 Base Case, but with a resource mix and a load forecast that consider potential system conditions further out. This will provide information to stakeholders about how key outputs and metrics may change with changes to the region’s power system and load.

ISO put forward a future base case for discussion at its January MC Meeting. Numerous stakeholders noted they would like to see higher penetration of renewables and progress towards a more decarbonized economy. To be responsive to that feedback, ISO is seeking input on the following additional cases to represent such additional cases. ISO will plan to use its January case as Future Resource Mix 1. The following questions primarily solicit input on Future Resource Mix 2 and 3.

6. For Future Resource Mix 2, the case I would be most interested to see would incorporate this many MW of each resource type beyond (additive to) the ISO’s Mix 1 includes the following (select one for each row):

Note: CELT 2026 will not be complete at the time the analysis will need to be set up and validated.

7. Future Base Case Year Loads for Resource Mix 2:
   For the base load assumptions, as a starting point, should the ISO use its 2025 CELT forecasts for (select one):

• 2035
• 2040
• 2045

8. For Future Resource Mix 3, the case I would be most interested to see would incorporate this many MW of each resource type beyond (additive to) the ISO’s Mix 1 includes (select one for each row):

9. Future Base Case Year Loads for Resource Mix 3:
   For the base load assumptions, as a starting point, should the ISO use its 2025 CELT forecasts for (select one):

• 2035
• 2040
• 2045

10. Once we arrive at the resource mix that we think the region is looking to see in the simulations, ISO will need to balance the load or retirements accordingly such that the system is somewhat balanced (e.g. meeting LOLE) for sensible results for the future case. Would you like the ISO to (select one):

• Adjust the load
• Adjust the quantity of oil deactivating
• Half and half

Note: ISO will use the relative ranking in questions 11 and 12 to jointly inform how it will match higher load levels with sensitivities that increase renewable penetration for efficiency in crafting sensitivities that are economically logical.

11. Future Base Case Load Sensitivities:
    Which load sensitivities are of greatest interest to you?
    Please rank these selections in the order of your preference.

12. Future Base Case Resource Mix Sensitivities:
    Which inputs are you most interested in varying in a sensitivity analysis to see how the outputs change?
    Please rank these selections in the order of your preference.

13. Additional Analysis Explaining Results: What potential additional analysis would be of greatest interest to you with respect to the ISO’s future mix 1 case? Please rank these selections in the order of your preference.

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