Hemmingway BESS
Battery storage power plant · Owyhee County, Idaho
Nameplate capacity
166 MW
Rank in Idaho
#11
of 156 plants
In service since
2025
March 2025
Details
- Primary fuel
- Battery storage
- Technology
- Batteries
- Operator
- Idaho Power Co
- County
- Owyhee County
- Generating units
- 3
- Share of state capacity
- 2.45%
- Rank among battery storage plants in Idaho
- #1 of 10
- EIA plant code
- 66325
Generating units
| Unit | Technology | Nameplate | Summer | Online | Status |
|---|---|---|---|---|---|
| 1 | Batteries | 80 MW | 80 MW | 2025 | Operating |
| 3 | Batteries | 50 MW | 50 MW | 2026 | Operating |
| HGWP2 | Batteries | 36 MW | 36 MW | 2025 | 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 Idaho
| Bennett Mountain | Natural gas | 173 MW |
| Rathdrum | Natural gas | 166 MW |
| Cedar Creek Wind, LLC | Wind | 160 MW |
| Boise Bench BESS | Battery storage | 150 MW |
About this data
From EIA’s inventory of operable generators, August 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 166 MW solar plant and a 166 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 Idaho power plants · What Idaho actually generates