Waterford — After years of Dominion Energy's hints that high costs and competition from historically cheap natural gas prices threatened Millstone Power Station's future, state regulators this year agreed to let the plant compete in a higher-priced market among solar, wind and hydropower producers.

This month, regulators additionally found the plant "at risk of early retirement" partly based on confidential financial data turned over by Dominion. The designation lets regulators consider the plant's substantial economic, environmental and grid benefits in the state's zero-carbon auction.

The state's moves to keep Millstone operational faced criticism from Dominion competitors, utilities and environmental groups who argued the plant should remain profitable for more than a decade. But regulators' decisions followed pressure from lawmakers concerned about the potential loss of 1,000-plus jobs. Regulators also said without Millstone delivering its 2,100 megawatts of electricity, the New England grid faced unreliability, and greenhouse gas emissions from replacement sources would undercut state environmental goals.

Regulators expect to select winning bidders in the zero-carbon auction by early 2019.

b.kail@theday.com