“Every megawatt-hour (MWh) of electricity produced by solar and wind farms displaces 1 MWh produced by a coal-fired power plant and 3 MWh of natural gas-fired electricity. (A megawatt-hour is the equivalent of 1 million watts produced continuously over an hour’s time by a power plant.)”.

Read More https://qz.com/131059/how-to-save-7-billion-by-greening-up-the-grid/

Ref: Todd Woody, 2013, “How to save $7 billion by greening up the grid”