It’s the end of an era for the region’s electric grid as New England’s largest fossil fuel-fired plant powers down for good.
The Mystic Generating Station in Everett has been a workhorse for decades. As the second largest power plant in New England, it has served as a powerful backup generator during times of extreme heat or cold when electricity is in high demand. But its owner, Constellation Energy, determined it was no longer cost effective to run Mystic’s two remaining gas-powered units, which have only operated about 10 percent of the time.
Grid overseer ISO New England arranged a contract to keep operating the units — which together can generate enough power for nearly 1.5 million homes — for the past two years, allowing time for utilities Eversource and National Grid to improve transmission lines to ensure the lights stay on in Greater Boston. The special ratepayer-funded contract expires at the end of the day on Friday, shuttering what’s left of the plant.
“It’s been a great thing for both ISO New England and the Greater Boston community to have such a reliable plant that can go up and down quickly to meet grid security requirements,” said Richard Levitan, a Boston-based energy industry consultant.
Levitan noted that Mystic’s importance to the grid came not just from its size but also its location on Boston’s doorstep. Next door to a liquefied natural gas import terminal, now also owned by Constellation, Mystic could draw directly from the imported supplies at the terminal rather than rely on domestic gas piped in to New England.
“Most other plants during cold snaps are starved for gas, and, if they’re operating, they’re operating on oil,” Levitan said. “But the Constellation Mystic plant could exploit its location by using LNG from the Constellation import terminal.”
Indeed, Mystic has been the LNG terminal’s largest customer, raising questions about its viability when the plant closes. But the state’s biggest gas utilities recently received approvals from the state Department of Public Utilities to keep the shipping terminal open for another six years, to ensure a steady supply of LNG for heating purposes. The cost of those six-year contracts will be picked up by the utilities’ gas customers.
Mystic’s closure reflects important shifts in the region’s energy mix.
The proliferation of rooftop solar panels has lessened the need for Mystic to be retained as a backup power source, ISO New England president Gordon van Welie said, as will the region’s first major offshore wind farm, Vineyard Wind, when it’s fully operational within the next year.
“We were comfortable enough that we could let it go,” van Welie said of Mystic’s closure. “It’s symbolic of the transition that’s underway [to cleaner energy sources].”
The Mystic plant sprawls across roughly 70 acres overlooking the Mystic River. Eight of its ten units have previously been retired; Constellation last year sold nearly 45 acres where the retired turbines sit to Wynn Resorts, which operates the Encore Boston Harbor casino across the street. The Kraft Group is considering construction of a 25,000-seat soccer stadium for the New England Revolution on the Wynn-owned portion. Meanwhile, Constellation is evaluating potential future uses for the remaining 26 acres, spokesman Mark Rodgers said.
The plant’s history dates back to World War II, when the company, then known as Boston Edison, built the first three units to help keep up with surging demand for electricity. The plant expanded over time and was eventually labeled by environmentalists as one of the state’s “Filthy Five” dirtiest plants, in large part because it burned coal or oil over the years, until the two natural gas-fired units opened in 2003.
About 40 employees stuck around to help run the remaining two units, Rodgers said. They’ve been offered other positions at Constellation, will remain on site to help with the decommissioning, or have agreed to separation packages.
The wind-down of the Mystic plant, once the city’s biggest taxpayer, has hurt Everett’s tax base: The city’s revenue from the power plant fell from $15 million a year in the 2010s to $5 million in 2024.
Mayor Carlo DeMaria said this shift underscores the importance of redevelopment. That’s why he is pushing the state Legislature to remove the Wynn-owned section from a state-regulated Designated Port Area, a change necessary to enable the stadium project. He added: “The financial picture clearly reflects the need for a private entity to be able to come in with a project that includes cleaning up a contaminated site and bringing in a new use to replace the taxes we lost.”
Jon Chesto can be reached at jon.chesto@globe.com. Follow him @jonchesto.
