How wind and solar became America’s cheapest energy source

The price of renewable energy has been dropping exponentially over the past decade—and shows no sign of reversing. In most of the U.S., it’s now become cheaper to build a new solar or wind farm than to keep an existing coal plant running.

Part of the reason is better technology—solar panels and wind turbines have gotten more effective at generating power. Economies of scale help, too: “When renewables get cheaper, we buy more, and then they get even cheaper and we buy even more,” one expert said.