Lower Monumental
Hydro power plant · Walla Walla County, Washington
Details
- Primary fuel
- Hydro
- Technology
- Conventional Hydroelectric
- Operator
- USACE Northwestern Division
- County
- Walla Walla County
- Generating units
- 6
- Share of state capacity
- 2.55%
- Rank among hydro plants in Washington
- #10 of 73
- EIA plant code
- 3927
Generating units
| Unit | Technology | Nameplate | Summer | Online | Status |
|---|---|---|---|---|---|
| 1 | Conventional Hydroelectric | 135 MW | 135 MW | 1969 | Operating |
| 2 | Conventional Hydroelectric | 135 MW | 135 MW | 1969 | Out of service but expected to return to service in next calendar year |
| 3 | Conventional Hydroelectric | 135 MW | 135 MW | 1970 | Operating |
| 4 | Conventional Hydroelectric | 135 MW | 135 MW | 1979 | Operating |
| 5 | Conventional Hydroelectric | 135 MW | 135 MW | 1979 | Operating |
| 6 | Conventional Hydroelectric | 135 MW | 135 MW | 1979 | Operating |
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
| Little Goose | Hydro | 810 MW |
| Lower Granite | Hydro | 810 MW |
| Transalta Centralia Generation | Coal | 730 MW |
| Grays Harbor Energy Facility | Natural gas | 715 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 810 MW solar plant and a 810 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