The sprawling former ExxonMobil tank farm on Everett’s Mystic River is on track to swap oil tanks for towering rows of batteries, after state regulators cleared construction of what is expected to be the largest battery energy storage site in both Massachusetts and New England. Jupiter Power’s Trimount Energy project calls for roughly 700 megawatts of power capacity and about 2.8 gigawatt-hours of storage on a portion of the industrial waterfront site.
According to company and state filings, the facility is designed to soak up extra electricity when the grid is under stress, then send that power back when demand spikes, in order to prevent outages and blunt price surges for customers.
What’s Being Built
Jupiter Power has filed with the state Energy Facilities Siting Board for individual and comprehensive zoning exemptions tied to an approximately 700 MW / 2,800 MWh battery energy storage system on about 20.75 acres of the former terminal. Trimount itself is expected to occupy roughly 16.5 acres of that footprint.
The petition also seeks approval to install two underground transmission lines, one at 115 kilovolts and one at 345 kilovolts, plus two new project substations that would connect directly into Eversource’s Mystic Substation. Those technical and land use details are spelled out in the Siting Board’s docket, according to the Energy Facilities Siting Board.
Project Specs and Claimed Savings
Plans show the system relying on lithium ion batteries stored in about 816 above ground enclosures. Roughly half of those containers would sit on industrial steel platforms, with the rest stacked below. Each container would be about 19.7 feet long, 7.9 feet wide and 9.5 feet tall.
Jupiter Power and project documents say the Trimount installation could help avoid or delay more than $2 billion in transmission upgrades through 2050 and ease pressure on the central Boston grid. "The recent approval of the Trimount Energy project by the Massachusetts EFSB will lead to billions of dollars of savings for electric consumers," Jupiter Power said in a statement, as reported by WCVB.
How It Fits Into The State’s Storage Push
Trimount was one of four projects selected in the first round of Massachusetts’ Section 83E storage solicitation in late 2025, an early slate aimed at adding mid duration storage to the regional grid. That initial procurement totaled roughly 1,268 megawatts and is intended to help tie in offshore wind and other renewables while cutting peak time costs for ratepayers, according to reporting on the state awards by Boston.com.
Permitting And Local Reaction
The Energy Facilities Siting Board has the authority to grant zoning exemptions that allow major energy projects to proceed even when local officials object, a procedural point spelled out in the Trimount filings with the state board, according to the Energy Facilities Siting Board.
Everett Mayor Carlo DeMaria has publicly pushed back on using the waterfront for a battery farm, arguing that the city should pursue denser mixed use redevelopment instead, a stance detailed in local coverage by The Boston Globe. Developers counter in project materials that environmental cleanup, projected tax revenue and the site’s direct tie in to the Mystic Substation make Trimount a logical first phase of the broader Docklands redevelopment vision.
Timeline And What’s Next
Project materials state that environmental remediation of Trimount’s share of the former oil terminal is already underway and is expected to wrap up in 2026. Construction would follow successful permitting and commercialization milestones.
Jupiter Power’s site notes that the company expects commercial operations in the latter half of the decade and is forecasting hundreds of construction jobs and more than $1 billion in investment in Everett, according to the project website.
