People have a long history of using the force of water flowing in streams and rivers to produce mechanical energy. Hydropower was one of the first sources of energy used for electricity generation and is the largest single renewable energy source for electricity generation in the United States.
In 2017, hydroelectricity accounted for about 7.5% of total U.S. utility-scale electricity generation and 44% of total utility-scale electricity generation from renewable energy sources. Hydroelectricity’s share of total U.S. electricity generation has decreased over time, mainly because electricity generation from other sources has increased.