Hydropower explained Where hydropower is generated

Most U.S. hydroelectricity generation capacity is in the West

There are conventional hydropower/hydroelectric facilities in nearly every state. Most hydroelectricity is produced at large dams built by the federal government, and many of the largest hydropower dams are in the western United States.

About half of total U.S. utility-scale conventional hydroelectricity generation capacity is concentrated in Washington, California, and Oregon.¹ Washington has the most conventional hydroelectric generating capacity of any state and is the site of the Grand Coulee Dam, the largest U.S. hydropower facility and the largest U.S. power plant in electric generation capacity. New York has the largest conventional hydroelectricity generation capacity of all states east of the Mississippi River, followed by Alabama.

In 2021, total U.S. conventional hydroelectricity net summer generation capacity was 80,027 megawatts (MW)—or about 80 million kilowatts.

• The top five states and their percentage shares of U.S. total conventional hydroelectricity net summer generation capacity in 2021 were:
• Washington27%
• California13%
• Oregon10%
• New York6%
• Alabama4%

Hydroelectricity generation varies with precipitation levels

Because hydroelectricity generation ultimately depends on precipitation, and precipitation levels vary seasonally and annually, the ranking of each state in annual hydroelectricity generation may be different from its ranking in generation capacity.

In 2021, total U.S. conventional hydroelectricity generation was about 260 billion kilowatthours (kWh), equal to about 6.5% of total U.S. utility-scale electricity generation.

• The top five states and their percentage shares of total U.S. conventional hydroelectricity generation in 2021 were:
• Washington27%
• Oregon11%
• New York11%
• California6%
• Tennessee5%

Pumped-storage hydro

In 2021, there was about 23,022 MW of total pumped-storage hydroelectric generating capacity in 18 states, and 5 states combined had 61% of the national total.

• The top five states and their percentage shares of total U.S. pumped-storage hydroelectricity net summer generation capacity in 2021 were:
• California17%
• Virginia14%
• South Carolina12%
• Michigan10%
• Georgia8%

Pumped-storage hydroelectric systems generally use more electricity to pump water to upper water storage reservoirs than they produce with stored water. Therefore, pumped-storage facilities have net negative electricity generation balances. The U.S. Energy Information Administration publishes electricty generation from pumped storage hydroelectric power plants as negative generation.

Most dams were not built for electricity generation

Only a small percentage of the dams in the United States produce electricity. Most dams were constructed for irrigation and flood control and do not have hydroelectricity generators. The U.S. Department of Energy estimated that in 2012, non-powered dams in the United States had a total of 12,000 MW of potential hydropower capacity.

Last updated: March 16, 2022