The Connecticut Department of Energy and Environmental Protection said Friday that it would begin seeking new contracts for carbon-free electricity from large power generators, including the Millstone Nuclear Power Station in Waterford.

The announcement marks the start of the agency’s latest round of “grid scale” clean energy procurement, which began in 2011.

Several years later, officials used that process to provide a lifeline to Millstone after its owner threatened to shut the plant down due to the difficulty of competing against lower-cost natural gas. As part of a 10-year contract that expires in 2029, Connecticut agreed to purchase half of Millstone’s output at the set price of $50 per megawatt hour.

Like all the grid scale clean energy contracts, utility customers pay a premium on Millstone’s power whenever it’s higher than the wholesale cost of electricity — typically determined by the price of gas. But when the cost of electricity rises above the contract price, customers receive a credit on their bills.

In an interview, DEEP Commissioner Katie Dykes said the agency’s latest round of bidding “could write a new chapter for the future of Millstone,” as well as the Seabrook Station Nuclear Power Plant in New Hampshire.

“Energy market prices are higher,” Dykes said, referring to the rising costs of both natural gas and electricity in New England. The result, she said, is that customers could get a better deal from nuclear and other forms of clean energy.

“Our context for this [request for proposals] is not necessarily driven by trying to prevent a retirement, but instead we think that there’s an opportunity through this RFP to potentially extend the hedging value of signing on to a long-term contract for Millstone’s output at a lower price, potentially than what we might see in the energy market and then providing that revenue certainty that we know these nuclear facilities prefer.”

Millstone produces about one-third of all the electricity generated in Connecticut, as well as the vast majority of the state’s carbon-free power. The plant’s two reactors are licensed to continue operating until 2035 and 2045, respectively, though its operators are seeking an extension that will allow Millstone to run for several decades beyond that.

The Millstone contract attracted scrutiny following a temporary spike in electricity prices in 2024. But Dykes said the deal with the two nuclear power plants together has saved utility customers $153 million over the last six years.

Susan Adams, a spokeswoman for Millstone’s owner, Dominion Energy, said in a statement Friday that company is reviewing DEEP’s latest procurement request with the “goal” of submitting a bid.

“We recognize that several New England states have expressed interest in participating, and DEEP has indicated it will coordinate bid evaluation and selection with those states, though details on that process have not yet been provided,” Adams said. “Importantly, Millstone’s existing power purchase agreement remains in place.”

In addition to nuclear, Dykes said DEEP will also accept proposals for solar, wind, energy storage, hydropower and associated transmission projects.

In its latest round of clean-energy procurement announced in December, the agency selected three solar projects in Connecticut and Vermont with a total output of 67 megawatts. That round was expedited to take advantage of federal tax credits that are being phased out by the Trump administration.

Other projects that have been selected under DEEP’s previous clean-energy procurement include the Revolution Wind farm off the coast of Rhode Island.

The bidding process has also at times highlighted challenges in the development of clean, affordable electricity. In order to be selected, projects must be deemed to be in the best interest of utility customers and any contracts to purchase power need to be reviewed and approved by the Public Utilities Regulatory Authority.

In 2024, Connecticut passed on selecting any new offshore wind projects after officials, including Gov. Ned Lamont, raised concerns about the cost of the bids. Since then, President Donald Trump’s efforts to halt offshore wind projects has dimmed the outlook for that industry.

“There’s quite a bit of uncertainty around what financing might look like,” for renewable energy projects, said Kate McAuliffe, a senior policy advocate at the Acadia Center, a nonprofit research and advocacy group focused on clean energy in the Northeast.

“I think that makes it even more imperative for the state to move quickly on this,” she added. “Anything that [DEEP] can do to expedite the process, whether that’s in permitting or approvals, to make sure that other mature projects can go online, that’ll be really important. And then the results that we see in response to this will be pretty illustrative of what the industry is going to look like.”

The year’s grid scale energy procurement will also be the first conducted under a new law requiring DEEP to coordinate with at least two other New England states over agreements to buy nuclear power. The states may also collaborate over non-nuclear, bids, though they are not required to do so. Dykes said that Massachusetts, Rhode Island, Vermont and Maine have all expressed interest in participating.

Dykes said that DEEP will also consider projects that have bid into a similar solicitation from Maine Public Utilities Commission for the development of on-shore wind and transmission lines in the northern parts of that state.

Lauren Savidge, the director of DEEP’s Office of Energy Supply and Infrastructure, said that officials will begin evaluating bids this spring, before announcing winners in the second quarter of this year. The state’s electric utilities, Eversource and United Illuminating, will then enter into negotiations with the winners before submitting any contracts for PURA review by the end of this year.