BOSTON — The NEPOOL Participants Committee voted nearly unanimously to support the first phase of ISO-NE’s capacity auction reform (CAR) project, which would transition the region to a prompt capacity market and reduce the notification timeline for generator deactivations from about four years to one year.
ISO-NE forward capacity auctions (FCAs) historically have been held over three years prior to each capacity commitment period (CCP). Under the proposed prompt auction format, auctions would be held about a month prior to each CCP.
RTO officials have said moving to a prompt auction would help address issues related to “phantom entry” — in which new capacity resources fail to achieve commercial operations in time to meet their supply obligations — and challenges associated with forecasting demand three years into the future.
The changes are intended to take effect for the 2028/29 capacity auction. While the proposal is designed to be able to stand on its own, ISO-NE plans to file an additional set of changes that also would take effect for the 2028/29 CCP. The second phase of CAR centers around capacity accreditation and splitting commitment periods into winter and summer seasons.
The prompt market changes generally are viewed as the less controversial of the two phases, though developing the proposal still requires extensive work and stakeholder engagement to reach a consensus on the details of the new design.
Under the prompt framework, only resources that have proved they are commercially viable would be able to participate in capacity auctions. The proposal would shorten the qualification process, eliminate annual reconfiguration auctions and move the auction from a descending-clock format to a sealed-bid format.
Much of the stakeholder discussions centered around changes to the resource retirement process, which ISO-NE views as a necessary component of the shift to the prompt market. Under the new prompt framework, ISO-NE proposes to separate resource retirement from the capacity auction process.
“The current four-year lead time to retire under a forward market would be replaced with a requirement that a resource submit a binding, irrevocable deactivation notice one year in advance of the start of the delivery period,” ISO-NE wrote in a memo published prior to the Dec. 4 PC meeting.
At the meeting, several stakeholders praised ISO-NE for its receptiveness to stakeholder input throughout the process. However, multiple participants voiced lingering concerns that moving to a prompt market may increase market volatility, especially as demand grows and the balance of supply and demand tightens.
Others have expressed concerns about impacts on resource development. Under a prompt auction, resources would have no certainty about capacity prices when making development decisions.
However, proponents of a prompt market have argued that the forward capacity market has done little to incentivize new development following the elimination of the seven-year price lock for new entrants in 2021. A general increase in the time it takes to develop most new resources has made it difficult to develop new resources based on capacity market outcomes. (See FERC Orders End to ISO-NE Capacity Price Locks.)
One stakeholder said they remain worried that a one-year deactivation notification timeline would increase the risk of reliability-must-run agreements.
Despite the handful of concerns, the proposal passed with broad support and just one opposition vote at the PC, after receiving widespread support from NEPOOL technical committees in November.
ISO-NE said it plans to incorporate a stakeholder amendment to maintain existing rules around “ambient air de-list bids,” which allow participants to reflect in capacity offers the physical limits of resources at high ambient temperatures. This amendment received 83% support from the Markets Committee in November. (See NEPOOL Committees Support ISO-NE Prompt Capacity Auctions.)
ISO-NE said it plans to file the changes with FERC by the end of 2025. Stakeholder discussions of the second phase of the CAR project are ongoing; ISO-NE is targeting a second filing by the end of 2026.
Operations Updates
Also at the PC, ISO-NE COO Vamsi Chadalavada gave an update on RTO operations, noting that energy market value for November 2025 was up by about 40% compared to November 2024.
He added that ISO-NE is closely following a spike in prices in the day-ahead ancillary services market; average daily day-ahead ancillary service costs have increased by about 260% since September.
ISO-NE launched the day-ahead ancillary services market in March. It plans to formally discuss how the market is working — along with any changes that may be necessary — with stakeholders in March 2026.
“We still think some time is helpful to go through the winter cycle to see how it performs in the winter,” Chadalavada said, adding that he remains confident in the basic design of the market.
“The objectives are not going to change. It is, for us, I think the best way to secure those services,” he said.
Chadalavada also discussed the capacity deficiency conditions that occurred Nov. 23, noting the event was triggered by unexpected outages at three gas-fired plants, along with higher-than-forecast load and lower-than-expected net imports. (See Unexpected Generation Loss Triggers Capacity Deficiency in ISO-NE.)
Initial data indicate the average balancing ratio for the event was 69.3%, while pay-for-performance penalties and credits totaled an estimated $34.7 million, he said.
The balancing ratio determines each capacity resource’s responsibility to provide energy and/or reserves during scarcity periods, while resource performance relative to these responsibilities determines charges and credits.

