As the U.S. and the globe transition away from harmful and polluting fossil fuels and into renewable energy sources, more researchers, policymakers, and developers are considering how much renewable energy we will need to deploy to replace outdated coal, gas, and liquid fuel hubs.
One journalist and technology expert tried to put the scale into perspective with their own calculations, finding that replacing a single mid-sized U.S. coal-fired power plant could require roughly 1 million solar panels.
Here's what to know
According to journalist Alan Bradley, writing for Slash Gear, a 500-megawatt coal plant is considered mid-sized in the United States. On a basic nameplate-capacity comparison, it would take about 1 million modern 500-watt solar panels to equal 500 megawatts — but that only matches peak output at a given moment.
To compare how much power each source really delivers, it helps to look at annual generation and capacity factor. Bradley, citing the Southern Renewable Energy Association, reported that U.S. utility-scale solar has averaged a capacity factor in the mid-20% range, while coal plants averaged 43% in 2023.
Because of that difference, a 500-megawatt solar project would not produce as much electricity over a year as a 500-megawatt coal plant, so the solar replacement would likely need significantly more installed capacity.
Coal also is not a perfectly steady source. Outages and other disruptions can leave coal and other fossil fuel plants offline about 12% of the time, Bradley noted.
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More background
Replacing coal with solar is not a direct one-for-one exchange on the ground, either. Utility-scale solar projects can require several acres per megawatt, meaning a buildout large enough to replace a coal plant's annual generation could take up a substantial amount of land.
Solar output rises and falls with available sunlight, so utilities often need battery storage or grid upgrades to keep electricity flowing after sunset and during low-light periods.
Despite the potential challenges, replacing coal-fired electricity can reduce the air pollution associated with asthma and heart disease while also cutting the heat-trapping pollution that fuels more extreme weather. Cleaner grids can also help shield households from fuel-price swings tied to coal and gas markets.
Coal-to-solar redevelopment tends to work best as part of a broader package that includes solar, storage, grid planning, and thoughtful land use.
What can be done?
Utilities and regulators can pair new solar projects with battery storage and grid upgrades instead of treating solar as a stand-alone replacement. That approach can make it easier to phase out polluting plants without undermining reliability.
Cutting electricity use through efficiency improvements, better insulation, and efficient appliances can reduce overall demand on the grid, making it easier for cleaner power sources to fill the gap.
Replacing a coal plant with solar is possible, but it takes more than a simple swap: more panels, other renewable energy sources, smarter grid planning, and storage systems can help turn abundant clean energy into reliable daily power.
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