(Reuters) - U.S. power companies expect to retire or convert from coal to gas over 10,600 megawatts (MW) of coal-fired plants in 2019 after shutting over 13,000 MW in 2018, according to U.S. Energy Information Administration (EIA) and Thomson Reuters data.

The number of megawatts retired in 2018 was the second highest in a year behind 2015 when generators shut over 19,000 MW. One megawatt can power about 1,000 U.S. homes.

U.S. coal power capacity peaked around 317,400 MW in 2011, according to EIA data. It has declined every year since and was down to around 244,000 MW by the end of 2018. The total generating capacity in the United States - including coal, natural gas, renewables and nuclear - was almost 1.1 million MW in 2018.

Cheap gas from record shale production and rising use of renewable sources of power have kept electric prices low in recent years, making it uneconomic for generators to continue operating older, less efficient coal plants, especially if they need upgrades to meet increasingly strict federal and state environmental rules.

Coal had been the primary fuel for U.S. power plants for much of the last century, but its use has been declining since peaking in 2007. That was around the same time drillers figured out how to economically pull gas out of shale formations.

Gas overtook coal as the leading fuel for U.S. power plants in 2016, according to federal data, and has held that title ever since.

It takes roughly 175 million cubic feet of gas per day of gas to generate about 1,000 MW.