Cobble Mountain
Hydro power plant · Hampden County, Massachusetts
Details
- Primary fuel
- Hydro
- Technology
- Conventional Hydroelectric
- Operator
- City of Holyoke Gas and Electric Dept.
- County
- Hampden County
- Generating units
- 3
- Share of state capacity
- 0.24%
- Rank among hydro plants in Massachusetts
- #5 of 32
- EIA plant code
- 1630
Generating units
| Unit | Technology | Nameplate | Summer | Online | Status |
|---|---|---|---|---|---|
| 1 | Conventional Hydroelectric | 13 MW | 13 MW | 1930 | Operating |
| 3 | Conventional Hydroelectric | 13 MW | 13 MW | 1930 | Operating |
| 2 | Conventional Hydroelectric | 7.0 MW | 6.8 MW | 1930 | 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 Massachusetts
| Wheelabrator North Andover | Other | 40 MW |
| Hadley Falls | Hydro | 33 MW |
| New England Wind LLC | Wind | 29 MW |
| Outer Cape Community Battery | Battery storage | 25 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 33 MW solar plant and a 33 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 Massachusetts power plants · What Massachusetts actually generates