(CNN) - The simple laws of economics threaten to doom America's remaining coal power plants.
Wind and solar costs have plunged so rapidly that 74% of the US coal fleet could be phased out for renewable energy -- and still save customers money, according to a report released on Monday by Energy Innovation, a nonpartisan think tank.
That figure of at-risk coal plants in the United States rises to 86% by 2025 as solar and wind costs continue to plunge.
The research demonstrates how it's increasingly more expensive to operate existing coal plants than build clean energy alternatives.
"US coal plants are in more danger than ever before," Mike O'Boyle, director of electricity policy at Energy Innovation, told CNN Business. "Nearly three-quarters of US coal plants are already 'zombie coal,' or the walking dead."
That's despite President Donald Trump's promise to revive the beleaguered coal industry. Trump declared the end of the "war on coal" and slashed regulations that clamped down on the emissions from coal-fired power plants.
Late last year, the administration announced plans to reverse an Obama-era coal emissions rule to make it easier to open new coal plants. Trump even appointed Andrew Wheeler, a former coal lobbyist, to lead the EPA.
"Trump administration efforts to cut environmental regulations are too little, too late to save coal," O'Boyle said.
Rust Belt coal plants under siege
The Energy Innovation report found that in 2018, 211 gigawatts of existing US coal capacity -- or 74% of America's fleet -- was at risk from local wind or solar that could more cheaply churn out just as much electricity.
North Carolina, Florida, Georgia and Texas are the US states that have the greatest amount of coal plants at risk from local solar and wind, the analysis found. Energy Innovation defined local as within 35 miles.
By 2025, Midwestern states including Indiana, Michigan, Ohio and Wisconsin are expected to have high amounts of coal capacity under pressure from renewable energy.
Of course, just because it may be economically feasible to shut down a coal plant and replace it with wind or solar, doesn't mean it will happen right away. State regulators must sign off on such decisions. And many power plants will decide to pass the extra costs on to customers.
Moreover, coal is still a major employer in parts of Appalachia, making any shutdown potentially damaging to the local economy.
Coal has been dethroned
Coal was the longtime king of the power industry before it encountered fierce competition last decade from natural gas. Not only is natural gas a cleaner burning fossil fuel, but it's in abundance in the United States thanks to the shale revolution. In 2016, natural gas surpassed coal for the first time as America's leading power source.
Meanwhile, the share of total power generation from coal-fired power plants plunged from 48% in 2008 to just 28% last year, according to government statistics.
And the rise of renewables means that the economics have once again swung against coal. Aided by a surge of investment in clean energy, solar prices have plummeted 90% since 2009 -- and they're projected to continue declining, according to Energy Innovation.
Against that backdrop, renewable energy is projected to be the fastest-growing source of US electricity generation for at least the next two years, according to a January report published by the US Energy Information Administration.
Utility-scale solar power is expected to increase by 10% in 2019 alone, while wind power is expected to vault ahead of hydropower for the first time, the EIA said.
"Coal's biggest threat is now economics, not regulations," O'Boyle said.
New Mexico pledges to go carbon free
Another challenge for coal: American households and businesses are increasingly clamoring for clean energy as they worry about climate change.
Households and businesses are installing their own solar panels. Small-scape solar generating capacity is expected to grow by 44% over the next two years, according to the EIA.
Pressured by voters, US states are adopting ambitious clean energy targets -- and they're framing them as job creators.
Last week, New Mexico Governor Michelle Lujan Grisham signed into law a bold plan that aims to source half the state's power from renewable energy by 2030. And by 2045, New Mexico plans to be 100% carbon-free.
Future generations "will benefit from both a cleaner environment and a more robust energy economy with exciting career and job opportunities," Lujan Grisham said in a statement.
California and Hawaii also recently passed 100% clean energy targets.
Some power companies are moving rapidly to adjust to this new environment.
Xcel Energy, a Minneapolis-based power company that serves western and Midwestern states, recently pledged to deliver 100% carbon-free electricity by 2050. The plan calls for doubling Xcel's wind power while slashing its dependence on coal.
All signs point to more and more power companies waking up to the new clean energy reality.
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