National Grid plc has asked Massachusetts regulators to approve a deal with Constellation Energy Corp. that could keep the Everett LNG terminal open to serve almost one million East Coast natural gas customers during periods of peak demand.

With its 1,400 MW Mystic Generating Station slated for retirement later in the year, Constellation has said the economics of keeping the Everett terminal open could be difficult without other major customers.

London-based National Grid told regulators it is seeking to extend gas supply agreements with the more than 5 million metric tons/year capacity import facility for six years. A Constellation spokesperson told NGI that, if approved, the agreement with National Grid could be an anchor deal for keeping the terminal open through the...