Hydroelectric power plants in the United States

Hydroelectric units in the 2025 EIA-860 data total 80.1 GW of nameplate capacity, 5.8% of the US fleet. It is the main source at 1,390 plants; Washington has the most, with 21.5 GW. More of today’s hydroelectric capacity came online in 1961 than in any other year (3,483 MW). The oldest unit still working went into service in 1891 at Whiting, Wisconsin.

When today’s hydroelectric capacity was built

Above the line: capacity still operable in 2025, by the year each unit came online. Below: hydroelectric capacity retired in each year, including plants that have closed completely (EIA’s retired-generator file).

States with the most hydroelectric capacity

Washington21.5 GW
California10.0 GW
Oregon8,360 MW
New York4,683 MW
Alabama3,318 MW
Arizona2,720 MW
Idaho2,696 MW
Montana2,684 MW
Tennessee2,520 MW
Georgia1,962 MW
North Carolina1,888 MW
South Dakota1,648 MW
South Carolina1,349 MW
Arkansas1,321 MW
Kentucky1,100 MW

Largest units

The single biggest hydroelectric generator is unit 22 at Grand Coulee, rated at 805 MW.

Plant	State	Unit size	Online
Grand Coulee	Washington	805 MW	1978
Grand Coulee	Washington	805 MW	1979
Grand Coulee	Washington	805 MW	1980
Grand Coulee	Washington	600 MW	1975
Grand Coulee	Washington	600 MW	1976
Grand Coulee	Washington	600 MW	1976
Dworshak	Idaho	259 MW	1974
Boundary	Washington	239 MW	1985

The 25 largest hydroelectric plants

Rank	Plant	State	Runs on	Capacity	First unit	Operator
1	Grand Coulee	Washington	Hydroelectric	6,809 MW	1941	U S Bureau of Reclamation
2	Chief Joseph	Washington	Hydroelectric	2,456 MW	1955	USACE Northwestern Division
3	Robert Moses Niagara	New York	Hydroelectric	2,429 MW	1961	New York Power Authority
4	John Day	Oregon	Hydroelectric	2,160 MW	1968	USACE Northwestern Division
5	The Dalles	Oregon	Hydroelectric	1,820 MW	1957	USACE Northwestern Division
6	Rocky Reach	Washington	Hydroelectric	1,349 MW	1961	PUD No 1 of Chelan County (WA)
7	Glen Canyon Dam	Arizona	Hydroelectric	1,312 MW	1964	U S Bureau of Reclamation
8	Wanapum	Washington	Hydroelectric	1,220 MW	2011	PUD No 2 of Grant County (WA)
9	Bonneville	Oregon	Hydroelectric	1,162 MW	1938	USACE Northwestern Division
10	Boundary	Washington	Hydroelectric	1,160 MW	1967	City of Seattle (WA)
11	Hoover Dam (AZ)	Arizona	Hydroelectric	1,039 MW	1936	U S Bureau of Reclamation
12	Hoover Dam (NV)	Nevada	Hydroelectric	1,039 MW	1936	U S Bureau of Reclamation
13	McNary	Oregon	Hydroelectric	990 MW	1953	USACE Northwestern Division
14	Priest Rapids	Washington	Hydroelectric	950 MW	1959	PUD No 2 of Grant County (WA)
15	Robert Moses Power Dam	New York	Hydroelectric	912 MW	1958	New York Power Authority
16	Wells	Washington	Hydroelectric	867 MW	1967	PUD No 1 of Douglas County (WA)
17	Little Goose	Washington	Hydroelectric	810 MW	1970	USACE Northwestern Division
18	Lower Granite	Washington	Hydroelectric	810 MW	1975	USACE Northwestern Division
19	Lower Monumental	Washington	Hydroelectric	810 MW	1969	USACE Northwestern Division
20	Oahe	South Dakota	Hydroelectric	786 MW	1962	USACE-Omaha
21	Shasta	California	Hydroelectric	714 MW	1944	U S Bureau of Reclamation
22	Brownlee	Idaho	Hydroelectric	675 MW	1958	Idaho Power Co
23	Wilson Dam	Alabama	Hydroelectric	667 MW	1925	Tennessee Valley Authority
24	Edward C Hyatt	California	Hydroelectric	644 MW	1968	California Dept. of Water Resources
25	Rock Island	Washington	Hydroelectric	629 MW	1931	PUD No 1 of Chelan County (WA)

All 1,390 in the finder