US Hydro Power Plants

The United States has 1,426 hydroelectric plants with a combined nameplate capacity of 102.2 gigawatts as of May 2026. This represents 7.3% of all US generating capacity. Hydroelectric capacity is spread across 48 states, though concentrated in a few: just five states hold half the fleet. Washington leads by a large margin, with 21,776 megawatts across 73 plants—21.3% of the national total and 68.7% of Washington's own generating capacity.

The largest hydroelectric plants are Grand Coulee in Washington at 6,809 megawatts, followed by Bath County in Virginia at 2,862 megawatts, Chief Joseph in Washington at 2,456 megawatts, Robert Moses Niagara in New York at 2,429 megawatts, and John Day in Oregon at 2,160 megawatts. California ranks second nationally with 13,728 megawatts, though its hydro capacity represents only 12.7% of the state's total generation. Oregon, New York, South Carolina, and Tennessee round out the top states.

The hydroelectric fleet spans nearly a century. Martin Dam in Alabama came online in January 1927, while Jackman in New Hampshire, the newest plant, entered service in February 2026. Though the fleet includes many small units, total capacity of 102.2 gigawatts makes hydro a substantial source of US electric generating potential.