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Mossyrock

Hydro power plant · Lewis County, Washington

Nameplate capacity
300 MW
Rank in Washington
#23
of 139 plants
In service since
1968
October 1968

Details

Primary fuel
Hydro
Technology
Conventional Hydroelectric
Operator
City of Tacoma - (WA)
County
Lewis County
Generating units
2
Share of state capacity
0.95%
Rank among hydro plants in Washington
#14 of 73
EIA plant code
3918

Generating units

Individual generating units at Mossyrock
UnitTechnologyNameplateSummerOnlineStatus
51Conventional Hydroelectric150 MW186 MW1968Operating
52Conventional Hydroelectric150 MW157 MW1968Operating

Nameplate is the maximum rated output; summer capacity is what the unit can reliably deliver on a hot day, which is typically lower.

Similarly sized plants in Washington

Frederickson Power LPNatural gas318 MW
Goldendale Generating StationNatural gas303 MW
Ferndale Generating StationNatural gas286 MW
Wild HorseWind273 MW

About this data

From EIA’s inventory of operable generators, May 2026 release. Capacity is nameplate — the maximum rated output of the equipment, not what the plant actually generates over a year, which depends on how often it runs. A 300 MW solar plant and a 300 MW nuclear plant have the same entry here and produce very different amounts of electricity.

“In service since” is the earliest in-service date among the units still listed, so a site rebuilt around newer equipment can read as younger than the site itself. All Washington power plants · What Washington actually generates