It’s a hot muggy day, and the coal-fired Homer City power plant is busy burning coal to produce electricity for a million homes. And with air conditioners running on high throughout the Northeast, the electrons coursing out of the facility literally hum along a high-voltage power line just outside the plant.

Homer City, with its three huge hourglass-shaped cooling towers and tall smokestacks, has been a mainstay of this farming community northeast of Pittsburgh since the facility was built in the 1960s. John and Maureen Vilcek have lived exactly one mile from the plant since the late 1970s. They raised their children here, and hardly notice the constant rumble emanating from the plant up the road.

“I’d much rather it be coal-fired than nuclear,” Maureen Vilcek says. “In the beginning, there was some fly ash we dealt with, but that went away in the first few years.”

Though the Vilceks say the plant has cleaned up, it’s still a big polluter. Homer City was recently ranked the top emitter in the country of the harmful pollutant sulfur dioxide. Even so, Maureen Vilcek doesn’t want it shut down.

“That’s a lot of the economy of this region,” she says. “I would hate to see something happen to this power plant.”

Doubling down on coal

Her worries about the plant’s future are well-founded. Around 200 coal-fired power plants have either closed or announced plans to shut down around the country. Low natural gas prices have made coal-fired electricity less competitive. But federal clean air rules are also forcing plants to make a choice: clean up—or shut down.

Homer City is cleaning up. James Shapiro of GE Energy Financial Services, the company that owns the plant, said that GE has been installing two enormous scrubbers which will reduce emissions of mercury and sulfur dioxide from its smokestacks—even though it’s expensive.

“We decided it was more prudent actually to go forward with this investment and ensure the ongoing existence of the station,” Shapiro said.

LISTEN: “Is there a ‘War on Coal?'”

The plant is paying for these upgrades because of a series of rules the EPA has implemented under the Obama administration. One of these rules is the 2012 Mercury and Air Toxics Standards (MATS), which required coal plants to reduce mercury, harmful gases and particulate pollution. That rule was dealt a blow earlier this year by the Supreme Court, which sent the rule back to the EPA because the agency hadn’t considered the cost of implementing it. But that court decision came after Homer City and other power plants had already spent the money to comply.

“The actual scrubbers are $750 million, but when you add [additional costs], it’s over a billion dollars,” Shapiro said.

It’s a tremendous amount of material and labor to build one of these units. Much of it has to be custom-built at the plant itself, says Todd Kollross, one of the engineers installing the plant’s new scrubber system. But GE decided to double down on Homer City.

“They’re banking on the plant, and if we didn’t put it in, the plant won’t run,” says Kollross. “So it was either you had to do it, or you were done.”

Coal cuts its losses

But not every plant owner is willing to plunk down hundreds of millions of dollars to keep pace with the EPA’s new air rules. In 2013, FirstEnergy announced it would close the Hatfield’s Ferry and Mitchell power plants near Pittsburgh. Stephanie Walton, a spokesperson for FirstEnergy, says the cost of compliance with MATS became too much—especially as the plants struggled to compete with cheap natural gas and a sluggish market.

“The plants were both losing money,” she says. “And that was a result of—at the time—current and projected economic conditions [of] low-cost electricity and low demand for electricity.”

FirstEnergy decided to put pollution controls on its six remaining coal-fired power plants in Ohio, West Virginia and Pennsylvania. But the two plants it closed were simply not making electricity cheaply enough to compete. The company had already put in $700 million in pollution controls at Hatfield’s Ferry. But when the EPA announced the mercury rules, the company decided to cut its losses on the plant.

A ‘War on Coal?’

For some, these closures are evidence that the federal government is pushing the coal industry too far.

“Some people call it—and I would tend to agree with them—a war on coal-fired power plants,” says Joe Duckett, an environmental engineer who’s watched the industry for 35 years.

Duckett, who sits on the Pennsylvania Department of Environmental Protection’s (DEP) Air Quality Technical Advisory Committee, says coal has been an easy target for regulators. That’s because unlike a steel mill, a power plant can’t be moved overseas if it gets more expensive to operate. If they add new scrubbers, those costs get passed on to ratepayers. He thinks the regulations are unfairly forcing coal companies to spend billions of dollars for increasingly small improvements to air quality. He points to Pennsylvania’s air quality, which has generally been improving in recent years.

“When you get down to some of the levels we’re now regulating, it is arguable how much bang for the buck you get,” he says.

But environmentalists say the pollution controls like the kind Homer City is installing are necessary.

“On an annual basis, the pollution from Homer City results in 250 premature deaths, 420 heart attacks, 3900 asthma attacks and 190 other types of hospital admissions,” says the Sierra Club’s Tom Schuster.

The EPA says particles like the kind Homer City emits kill thousands of people a year, and the plant’s new scrubbers will keep much of this pollution from pouring into western Pennsylvania skies. Schuster says if coal wants to compete with other types of energy, it will have to do it cleanly.

“Coal can be clean, and coal can be cheap. But it can’t be both at the same time.”

And it will only get harder for coal, Schuster says. The EPA’s new climate rules target that other harmful byproduct of burning coal—climate-altering carbon dioxide. Plant owners say they’re still not sure whether they can—or what they’ll have to do to—keep up with another new rule.