A clean energy milestone was set in 2020 when renewables surpassed coal in electricity generation, according to Inside Climate News.

The continuing rise of wind and solar power, its low cost, and the steady performance of hydroelectric power, all contributed to U.S. renewable energy sources for the first time generating more electricity than coal.

Electricity producers are responding to the low costs of gas, wind and solar and are backing away from coal because of high costs and concerns about emissions.

Coal was the country’s leading electricity source as recently as 2015, and has fallen 42 percent since then, as measured in electricity generation.

Energy companies have been closing coal-fired power plants, and the ones that remain have been running less often than before.

Read more: A Clean Energy Milestone: Renewables Pulled Ahead of Coal in 2020