State environmental regulators are moving toward a deal that would let Maine’s largest oil-fired power plant skirt the latest pollution controls, igniting a debate over whether the aging facility is a vital energy safety net or an expensive smog-producing relic.

The Department of Environmental Protection has issued a draft order for a clean air exemption for Wyman Station on Yarmouth’s Cousins Island. Owned by NextEra Energy, the peaking plant runs mainly when there is high demand for electricity or when other plants go offline.

The decision carries consequences for both the region’s energy security and its climate mandates as New England struggles to prevent blackouts during extreme weather while transitioning away from fossil fuels.

Yarmouth residents contend that Wyman Station burns the thick, viscous, bottom-of-the-barrel oil most in need of the costly “scrubber” technology that reduces nitrogen oxide emissions. These emissions are a primary contributor to ground-level ozone, a known trigger for the state’s high rates of pediatric asthma, according to the Maine Center for Disease Control and Prevention.

NextEra Energy argues that installation of modern Selective Catalytic Reduction systems, which are essentially giant catalytic converters, would cost upward of $100 million, an investment that it claims is impractical for a facility that operates fewer than two weeks a year.

The company has said that installing modern scrubbers would cost as much as $236,000 per ton of nitrogen oxide removed because the plant runs so infrequently. State regulators usually consider $5,000 to $10,000 per ton “reasonable.” From 2020 to 2004, Wyman generated 62 tons of nitrogen oxide a year.

At a public meeting Thursday, Jane Gilbert, DEP’s air licensing unit manager, explained the draft order concludes the plant is eligible for a clean air exemption because the high-tech scrubbers are not “reasonably available” due to “technological and economic feasibility.”

Critics, however, argued the economic excuse is a mathematical sleight of hand.

Luke Frankel, an environmental scientist at the Natural Resources Council of Maine, said that estimates based on the last five years of plant operations make the cost of new equipment per ton of emissions look artificially high.

State analysis using data from the 10 years before that, when the plant was more active, would show Wyman had produced four times the amount of nitrous oxide a year. To use that higher cost estimate, NextEra should have to commit to maintaining a low-emitter status, Frankel said.

The meeting highlighted a growing frustration among those living in the shadow of the plant’s 421-foot stacks. Ed Simmons, a Cousins Island resident of 40 years, recalled past efforts to curb the plant’s pollution, describing them as collaborative, but said the current exemption goes too far.

“It does not make sense to exempt them from any of the standards,” Simmons said. “They’re still part of the New England grid and should be held to the same standards as all power plants, not just looking at their usage in recent years.”

Legal advocates challenged the narrative that the plant must be exempted to keep the lights on.

Sean Mahoney, executive vice president of the Conservation Law Foundation, said the regional transmission organization already has the authority to waive emission limits if the system is truly “crashing,” meaning the plant could still operate in a crisis even with stricter rules.

“In a state where we have a strong climate action plan, it’s imperative we put the most protective measures on to the operating plants, particularly outdated plants like this that are proposing to run for another 13 years,” Mahoney said.

He suggested the exemption request was more about NextEra’s profit than regional reliability.

The stakes are expected to rise as New England’s energy demands shift. Ivy Frignoca, the Casco Baykeeper with the nonprofit Friends of Casco Bay, warned that by 2032, the region is expected to operate in winter peak conditions at all times due to increased electrification.

“If there’s a chance that Wyman Station is going to be called upon, especially in the winter, to operate more and more, then we need to protect our air quality,” Frignoca said. She echoed the call for the plant to be reclassified as a “minor source” if it refuses to modernize.

Wyman Station is not the only power plant in Maine that burns oil, but it is the largest. With a capacity of 850 megawatts, according to state records, Wyman can power roughly 800,000 homes and burn up to 10,000 barrels of oil a day when running at full tilt.

The other Maine plants that burn oil, like Bucksport Generation and Westbrook Energy Center, treat it as a backup to natural gas. The University of Maine still uses an oil-fired boiler to heat its campus. Some paper mills have oil-fired boilers as backups for natural gas or biomass generators.

What happens at Wyman affects the electrical grid that serves all of New England. If one of the region’s last oil-fired plants becomes too expensive to run because of emission rules, the price of electricity throughout New England is likely to rise, company officials say.

The state will accept public comments through May 8. A final ruling is expected this summer.