Eversource breaks ground on nation’s largest underground electrical substation in Cambridge, Mass.
(UI) — Eversource has broken ground on the Greater Cambridge Energy Program (GCEP), a major transmission initiative designed to address rising electricity demand while enhancing grid resilience. The project includes the nation’s largest underground substation, spanning 35,000 square feet and located 105 feet below a new public green space in Cambridge.

The underground infrastructure is designed to support electrification and decarbonization efforts, helping the region transition away from fossil fuels. The substation’s output will enable full electrification of residential heating in Cambridge and could displace half of the commercial sector’s gas demand.
“Working with our partners at BXP, the Cambridge Redevelopment Authority, and the City of Cambridge, the Greater Cambridge Energy Program is a creative solution that helps shape a more sustainable and resilient energy future for our customers in the region,” said Eversource Chairman, President, and CEO Joe Nolan.
The project also includes eight new 115 kV underground transmission lines spanning 8.3 miles through Cambridge, Somerville, and Boston, along with upgrades to five substations in Cambridge, Somerville, and Allston/Brighton. In total, 48 new distribution lines will be added.
“This region is experiencing a surge of new residential and commercial development while at the same time moving away from fossil fuels,” said Cambridge City Manager Yi-An Huang. “This generates a growing demand for a reliable electrical grid. The Greater Cambridge Energy Program helps address the increased energy needs in the region, enhance the resiliency and reliability of the grid, and support the decarbonization goals of both Cambridge and the Commonwealth.”
Eversource expects to begin putting parts of GCEP into service by 2029, starting with the substation and the first transmission line. The remaining transmission lines will be activated through 2031. The project is anticipated to support approximately 500 full-time jobs during construction.
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