By William Opalka

Dynegy’s purchase of Energy Capital Partners’ New England power plants will immediately make it a major participant in a market where it has been a bit player.

Dynegy’s only presence in ISO-NE is the gas-fired 540-MW Casco Bay Energy Facility in Maine. The company is acquiring four combined-cycle gas generators in Massachusetts and Connecticut totaling 1,902 MW, in addition to the Brayton Point station in Massachusetts, a 1,510-MW coal-fired power plant that is slated for closure in May 2017.

Dynegy said it will retire Brayton Point on schedule. But for the two years that it will operate the plant, Dynegy will rival Exelon at the top of the generation market-share rankings in New England.

Calpine announced yesterday that it is purchasing Exelon’s 809-MW Fore River generating station in Massachusetts. The deal, expected to close in the fourth quarter, would make Calpine the eighth-largest generator in New England, up from 13th.

Including all of the ECP plants, Dynegy will have about 200 MW more than Exelon once the Fore River sale is complete.

Excluding the coal plant, the ECP acquisition will put Dynegy in fifth place, behind Exelon, Dominion Resources, GDF Suez Energy and NextEra Energy. About 10% of Dynegy’s portfolio will be located in New England.

ISO-NE said it is planning for the loss of Brayton Point with a study to identify transmission upgrades needed to move power into southeastern Massachusetts and Rhode Island.

“Private investors can also come forward with proposals for generation or demand-side resources that could address the reliability concerns,” ISO-NE spokeswoman Marcia Blomberg said. “If the needed transmission upgrades or resource proposals aren’t in service by the time that Brayton Point retires, the ISO and transmission owners will have special transmission operating plans in place to deal with unexpected transmission or generation outages.”