Amid the push for a cleaner future, a proposed power plant threatens to escalate the war over the region’s power grid

Proponents of the controversial project say it’s needed to promote the grid’s reliability and to control potentially costly fluctuations in energy prices, even though its fuel — oil and gas — has become more expensive than wind, solar, and other renewable energy. Over the long term, they say, it should provide significant savings to ratepayers in Peabody and the other communities that have agreed to finance it.

Opponents say it would hinder the state’s ability to comply with the sweeping new climate law, which requires Massachusetts to reduce its carbon emissions 50 percent below 1990 levels by the end of the decade and effectively eliminate them by 2050. They add that its 90-foot smokestack would also spread harmful particulate matter in surrounding vulnerable, lower-income communities, exacerbating asthma and other respiratory illnesses.

“We acknowledge that there’s a global problem from climate change, but we see this as necessary to address the [grid’s] reliability needs, and our costs,” said Charles Orphanos, manager of the Peabody Light Department, which has agreed to purchase nearly a third of the plant’s power.

He and other supporters of the project insist it would also benefit the environment. The new plant would be more efficient and produce fewer emissions than existing peakers, which are fired up mainly on the coldest and warmest days of the year to ensure there’s sufficient power. Most can run on either oil or gas, so they can operate during shortages and price spikes of either fuel.

“This will displace emissions,” Orphanos said. “This new unit has state-of-the-art emissions controls.”

Opponents of the project say it’s ludicrous for the state to sanction a new fossil fuel plant, noting that construction would start less than a year after Governor Charlie Baker signed the state’s landmark climate law and just a few weeks after world leaders gathered for a global climate summit in Glasgow and vowed to reduce their emissions sharply in the coming years.

Any new source of emissions, especially one that seeks to continue the use of fossil fuels for decades to come, is detrimental to the cause of eliminating emissions as soon as possible, they contend. Moreover, the hefty cost would be better spent on energy projects that would produce emissions-free power or on plants that use batteries to store that power for peak demand, they say.

This month, concerned residents held a rally in front of Peabody District Court, where they carried signs with messages such as: “Non-Renewable Energy is Peak Stupidity” and “Stop Polluting.”

Judith Black waved to passersby dressed in a costume composed of three vertical tubes made to look like smokestacks.

“The idea of building a fossil fuel facility, at this time in history, is an abomination,” said Black, 70, a member of the group Breathe Clean North Shore. “We’re standing at the edge of our extinction, because of the use of fossil fuels. Why on earth would we burn more?”

She and other protesters raised concerns about the ultimate amount of pollution produced by the plant, noting that the state has permitted it to operate for five times longer than the estimated 239 hours a year that developers say it would run and emit more than seven times the 7,085 tons of carbon dioxide they say it would release in a typical year. The state’s permits are based on the maximum output of the plant allowed; the developers say it will rarely operate at those levels.

They also described the plant as an “economic boondoggle,” contending it would probaby become a “stranded asset,” as the use of oil and gas are expected to be phased out before residents pay off its costs.

“It’s just a bad investment to put more money into fossil fuel infrastructure,” said Sarah Dooling, executive director of the Massachusetts Climate Action Network, who helped organize the rally. “The logic of this is perverse. Investing in dirty energy just creates more pollution. This is unacceptable and must stop.”

Last week, they delivered a petition with more than 1,000 signatures to Kathleen Theoharides, the state’s secretary of energy and environmental affairs, urging her to conduct a community health impact assessment and reevaluate the project’s potential environmental impact.

State officials didn’t respond to questions about whether they would reevaluate the project. In an e-mail, however, they noted the state had approved permits for the peaker before the climate law took effect.

“The legislation explicitly directed that these requirements apply to ‘new projects,’ ” wrote Craig Gilvarg, a spokesman for the Executive Office of Energy and Environmental Affairs.

He added that provisions in the law that require the state to take historical and existing pollution into account when deciding whether to approve a project were to “inform future decisions, not past and fully permitted projects.”

Officials at the Massachusetts Municipal Wholesale Electric Company, which is overseeing the plant’s development, said the proposal has already received a “rigorous” health and environmental review, and that emissions would be “well below the stringent state and federal ambient air quality standards.”

“We’re not the bad guys,” said Kate Roy, a spokeswoman for the company, which has committed to making the peaker operational in 2023. “Even under a worst-case scenario, the environmental impacts fall below the standard for what needs to be mitigated.”

After hearing concerns from local residents this year, the company made a few concessions, eliminating plans to build a 200,000-gallon storage tank for oil and using less toxic chemicals to scrub their emissions. Company officials also said they plan to retire one of two existing peakers in Peabody, both of which are more polluting, but they wouldn’t say when that would happen.

They considered other options, such as a battery plant, but it wasn’t a feasible alternative to the peaker, which should help stabilize their rates for decades to come, they said.

“For us, that’s important,” Roy said. “If our light departments didn’t have this, they would have to buy off the market, and those prices fluctuate.”

Roy said the company was complying with the requirements of ISO New England, which operates the region’s grid.

While the company supports the transition to renewable energy, there have to be power plants that operate when the wind isn’t blowing and the sun isn’t shining, she said. To underscore that continuing demand, she pointed to a footnote in the climate law that recognized “a need for limited greenhouse gas emissions in 2050.”

“That’s why the law calls for net zero — not zero emissions,” she said.

Matt Kakley, a spokesman for ISO New England, said it’s up to municipal light departments to decide what energy sources they build or buy into.

“The ISO has no role in those decisions,” he said.

The grid operator, by law, can’t factor environmental decisions into which energy sources it relies on; it can only base its decisions on cost and reliability.

“We’ve been advocating for years for putting a price on carbon, but we haven’t been successful,” Kakley said. “Until and unless we’re given the authority to put those environmental attributes into the market, we can’t account for them.”

At the rally in Peabody, protesters said such a change would go a long way to preventing future fossil fuel plants from being built in the region.

“Their regulations force us into these kinds of choices,” said Susan Smoller, 68, a retired school librarian in Peabody and one of the founders of Breathe Clean North Shore. “There needs to be a discussion of other ways of doing things. We need to change the rules, so this doesn’t happen again.”

David Abel can be reached at david.abel@globe.com. Follow him @davabel.