By William Opalka

FERC on Thursday denied rehearing of its approval of Constellation Energy’s acquisition of five New England power plants, a deal proposed five years ago (EC10-85).

NSTAR Electric challenged the sale of five power plants in the Boston area worth about 2,654 MW from various entities to Constellation for $1.1 billion. The sale represented about 8% of the generation fleet within the ISO-NE footprint at the time.

NSTAR claimed that the deal would harm competition in the New England energy market. FERC, however, approved the transaction as in the public interest.

NSTAR requested a rehearing, saying in part that two gas-fired plants originally owned by Mystic Power were susceptible to common mode failure because they both depended on a connection to a Distrigas liquefied natural gas terminal for their fuel. This condition, NSTAR said, could lead to the simultaneous loss of fuel supply, which would drive up consumer costs due to an increased reserve requirement by ISO-NE.

FERC in its order last week said this infrastructure issue was outside of the scope of the acquisition and noted that a 2006 settlement regarding the issue imposed conditions on the plant owners and subsequent buyers.

While the FERC docket for the case has been dormant since June 2011, when Constellation filed a response to NSTAR’s complaint, the companies have undergone significant changes of their own.

Original plaintiff NSTAR merged with Hartford, Conn.-based Northeast Utilities in April 2012 to create the region’s largest distribution utility that has since been renamed Eversource Energy.

Constellation was acquired by Exelon in March 2012. In 2014, Exelon sold one of the plants in the original deal, the 688-MW Fore Generating Station, to Calpine for $530 million, marking that company’s entry into New England.