Dive Brief:

• Capacity prices in ISO New England's four capacity zones were flat or fell in the grid operator's most recent forward capacity auction, with total estimated capacity revenue falling nearly 25% to $1.04 billion from $1.36 billion a year ago, according to results released Wednesday.

• About 311 MW of new generation, consisting of solar, battery storage and hybrid projects, won capacity obligations in the auction, down from about 950 MW of new resources last year, according to ISO-NE, the grid operator for the six New England states.

• Looking ahead to future auctions, offshore wind resources will likely begin replacing existing generating plants in ISO-NE's capacity auctions, Joe Prosack, a power analyst with ESAI Power, said Thursday.

Dive Insight:

The auction results don't include NTE Energy's planned 650-MW, natural gas-fired power plant in Killingly, Connecticut.

The Federal Energy Regulatory Commission in January approved ISO-NE's request to terminate a capacity supply contract for the plant for failing to meet development milestones. In response to a suit by NTE Energy, the U.S. Court of Appeals for the District of Columbia Circuit stayed FERC's decision. The court lifted the stay on March 2, allowing ISO-NE to release the auction results.

In the auction held in early February, 32,810 MW of resources won capacity commitments for the 2025-26 capacity year, down from 34,621 MW for the 2024-25 capacity year.

Through its capacity auction, ISO-NE lines up capacity supplies three years in advance to make sure it has enough resources to provide electricity in New England.

Solar, wind, storage and demand resources totaling nearly 5,000 MW cleared the auction, according to ISO-NE. That includes about 700 MW of storage and 500 MW of solar. About 3,323 MW of demand resources, which includes energy efficiency, load management and distributed generation, won capacity obligations, down from 3,891 MW last year.

About 257 MW of retirement and permanent de-list bids to leave the capacity market cleared before and during the auction compared with 242 MW last year.

Capacity prices in ISO-NE's southeast region — northeastern Massachusetts, Greater Boston, southeastern Massachusetts and Rhode Island — plunged 34% to $2.64/kW-month from $3.98/kW-month a year ago.

Prices in ISO-NE's northern region inched up to $2.53/kW-month from $2.48/kW-month and prices in its "rest of pool," which covers Connecticut and western and central Massachusetts, slipped to $2.59/kW-month from $2.61/kW-month.

Amid the shift in prices, significant changes could be in store for New England's resource mix, according to ESAI's Prosack.

"There is a surplus of capacity in ISO New England, so there [are] a lot of existing resources that I would say are at risk to retire, but have not retired yet," Prosack said. "At the same time, there is a good chunk of new capacity that will want to enter the [forward capacity market,] specifically offshore wind resources in the coming years."

"We're likely to see an exchange between those two resource types," Prosack said. "The more expensive older resources that are at risk to retire that will be displaced by new offshore wind resources."

Those changes will be influenced by pending rule changes, such as a proposal by ISO-NE to extend its "minimum offer price rule" by two years, according to Prosack.