Two-unit pumped storage beneath Bear Swamp in western Massachusetts
Bear Swamp is an underground pumped-storage station in Berkshire County, Massachusetts. Its two reversible units total 666 MW of current EIA nameplate capacity; Brookfield project materials commonly describe 600 MW of operating capability.
Answers use this researched asset profile with live ISO-NE data. Ask about ownership, equipment, project history, or current grid context.
Live ISO-NE public data · answers can be wrong, verify against source data or the ISO.
Two 333 MW generator records.
Brookfield's operating-capability basis, shown separately from EIA nameplate.
Francis pump-turbine motor-generators.
Similar plants ranked by technology, capacity, and distance.
Operating generator records and technology attributes reported through EIA-860.
| Generator | Capacity | Technology | Operation | Status |
|---|---|---|---|---|
| GEN1 | 333 MW 333 MW summer | Hydroelectric Pumped Storage Water · PS | Sep 1974 | Operating |
| GEN2 | 333 MW 333 MW summer | Hydroelectric Pumped Storage Water · PS | Oct 1974 | Operating |
Monthly EIA generation history and recent market-resource behavior where linked telemetry is available.
EIA-923 reports gross generation and net grid exchange for storage plants. Gross generation is shown as a discharge proxy; it is not a cycle count or conventional capacity factor.
Deterministic links to ERCOT market resources, price records, outage disclosures, queue records, and nearby infrastructure. Candidate joins remain labeled until corroborated.
Parties, market resources, and identifiers tied to this asset, with owner, operator, developer, EPC, compliance provider, and interconnecting entity roles kept separate.
| Largest reported plants | Capacity | State | |
|---|---|---|---|
| Bear SwampCurrent | 666 MW | MA | |
| Fife Brook | 11.2 MW | MA |
Portfolio membership follows the latest EIA-860 reporting entity. It does not imply ultimate ownership.
View full reporting portfolioProject milestones and public references behind the asset profile.
EIA-860 lists generator GEN1 with this operating date.
EIA-860 lists generator GEN2 with this operating date.
Answered from the published record above. Questions whose inputs this profile does not carry are omitted rather than estimated.
Bear Swamp has a reported capacity of 666 MW. Source: EIA Form 860M.
Bear Swamp is a Hydroelectric pumped storage facility in Berkshire County, MA, participating in the ISO-NE market.
Bear Swamp is in Berkshire County, MA, inside the ISO-NE balancing area.
Bear Swamp is operated by Bear Swamp Power Company LLC according to the EIA generator inventory. Reporting membership does not by itself establish ultimate ownership.
Bear Swamp reported 636.3 GWh over the twelve months to 2026-04. For a storage plant this is reported gross generation — a discharge proxy, not a cycle count or a conventional capacity factor.
By capacity, Bear Swamp ranks #12 of 39 operating plants of the same technology nationally. It ranks #2 of 2 in MA.
Plants within 25 km, nearest first, regardless of technology. Proximity is straight-line distance between mapped plant coordinates; it does not by itself establish a shared point of interconnection.