# Northfield Mountain

ISO-NE asset profile · https://askthegrid.com/assets/facilities/northfield-mountain

Northfield Mountain LLC - Franklin County - ISONE

Northfield Mountain is an operating four-unit, 1,168 MW pumped-storage plant built underground beside the Connecticut River in Massachusetts. FirstLight operates the facility, which can generate at full output for about 7.5 hours. The plant continues to operate under annual federal licenses while relicensing is pending.

## Metrics

- **Nameplate capacity:** 1168 MW — Canonical EIA plant baseline.
- **Registry anchor:** Plant 547 — plant-547

## Facts

- **Technology:** Hydroelectric Pumped Storage
- **Operator:** FirstLight Power Resources, Inc. - MA

## Related parties

- **Owner:** Northfield Mountain LLC — owner and FERC licensee ([source](https://www.northfield-relicensing.com/))
- **Owner / investor:** Public Sector Pension Investment Board (PSP Investments) — owner of FirstLight USA and ultimate parent ([source](https://www.investpsp.com/))
- **Acquirer:** Hull Street Energy, LLC — prospective owner pending regulatory approval (announced May 19, 2026) ([source](https://hullstreetenergy.com/))
- **Former owner:** Energy Capital Partners — portfolio owner 2006–2008 ([source](https://www.ecpgp.com/equity/portfolio/firstlight-power-enterprises-inc))
- **Former owner:** Northeast Utilities / Northeast Generation Company — original portfolio owner and 2006 seller ([source](https://www.eversource.com/))
- **Former owner:** GDF SUEZ / ENGIE Group — portfolio owner 2008–2016 ([source](https://www.engie.com/))

## Sources

- [firstlight.energy](https://firstlight.energy/firstlight-power-statement-on-flows-and-fish-passage-settlement-filing-for-northfield-mountain-and-turners-falls-hydropower-projects/) — firstlight.energy · public_source — Source retained for exact-record publication review.
- [frcog.org](https://frcog.org/wp-content/uploads/2024/06/FRCOG-Motion-to-Intervene-standing-declaration-04-16-24.pdf) — frcog.org · public_source — Source retained for exact-record publication review.
- [frcog.org](https://frcog.org/wp-content/uploads/2024/06/FRCOG-REA-comment-letter-on-TF-NFM-signed-05-22-24-optimized.pdf) — frcog.org · public_source — Source retained for exact-record publication review.
- [hullstreetenergy.com](https://hullstreetenergy.com/blog/hull-street-energy-to-acquire-firstlights-u-s-generation-fleet) — hullstreetenergy.com · public_source — Source retained for exact-record publication review.
- [northfield-relicensing.com](https://northfield-relicensing.com/content/Documents/DLA_Initial_Statement_and_Additional_Information.pdf) — northfield-relicensing.com · public_source — Source retained for exact-record publication review.
- [tnemec.com](https://tnemec.com/projects/northfield-mountain-hydroelectric-facility/) — tnemec.com · public_source — Source retained for exact-record publication review.

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Canonical page: https://askthegrid.com/assets/facilities/northfield-mountain
Website: [Northfield Mountain LLC](https://www.northfield-relicensing.com/)

Source: Ask the Grid — https://askthegrid.com/