Similar to calculating the number of solar panels needed to power your home, determining how many solar panels would be required to replace a coal plant is a complicated question. It's a common belief that, compared to the relatively steady energy production of a coal plant, solar panels only produce power when the sun is shining. That said, a useful way to frame this question is to pick a specific coal plant size. Let's use a 500-megawatt coal plant, which is a mid-sized plant in the U.S. So, to replace the same annual electricity production from that 500-megawatt coal plant, you would likely need substantially more capacity than the solar plant's rated output suggests.