Flatiron closes about $850M for a 1,200 MWh battery in Chelsea, Mass.

Flatiron Energy said on October 15, 2026 that it has closed approximately $850 million of construction and term financing commitments for Energizar, a battery storage project in Chelsea, Massachusetts. The release describes Energizar as a 1,200 MWh asset that will reach commercial operations in the fourth quarter of 2027, at which point, Flatiron says, "it will be the largest BESS facility on the east coast and one of the largest urban BESS facilities globally."

The money comes in five forms: construction and bridge loans, term loans, letters of credit, a preferred equity commitment and a tax credit transfer commitment. Nord L/B, Santander and Societe Generale were coordinating lead arrangers on the bank debt, with Investec and East West Bank as joint lead arrangers and Siemens Financial Services as a lender. The preferred equity came from funds managed by an unnamed credit manager with more than $350 billion of assets under management, and two unnamed Fortune 500 companies committed to buy a portion of the project's investment tax credits. The release does not say how the $850 million splits among those pieces.

Flatiron has held a regional title before. In September 2025 it announced financing for Taft, a 200 MW / 800 MWh battery in Uxbridge, Massachusetts, under the headline "Flatiron reaches financial close on largest battery energy storage project in New England." The new release moves the claim to the whole East Coast.

A state contract on a fast track

The close came six days after Massachusetts regulators cleared the approval that Energizar said stood between it and its financing. Energizar is one of three projects whose contracts Eversource, National Grid and Unitil filed with the Department of Public Utilities on July 2, 2026, from the first solicitation under Section 83E, the 2024 provision that has the utilities contract for approximately 5,000 MW of storage by July 31, 2030. Energizar's contracts buy only environmental attributes: Clean Peak Energy Certificates from 80 percent (200 MW) of the 250 MW project, over twelve years, at a fixed $32.75 per certificate. The alternative compliance payment those certificates are measured against is $65 per certificate through 2032 and $45 thereafter, according to the department's September 29 letter order, which found the contracts cost-effective.

Energizar had asked for approval by September 30, 2026 so it could break ground in the fall, and the department split its contracts from the other two projects' to deliver that, approving them on September 29. A footnote warned that such acceleration "remains an exception and we caution parties against relying upon our decision to issue this Order on an expedited timeframe in future proceedings." A second footnote, footnote 6, left cost recovery for the department's final order on the remaining contracts, due by January 4, 2027. That turned out to matter. The utilities moved for reconsideration on October 2, saying the contracts' "Regulatory Approval" condition was not met without those findings, and Energizar told the department on October 5 that it could not draw on its financing until they were made.

The department granted the motion on October 9. It said it had intended the September 29 approval to let the Energizar contracts proceed immediately, called any doubt that the cost-recovery footnote left about that approval inadvertent, and approved cost recovery plus the utilities' remuneration of 2.25 percent of annual contract payments. Energizar has put a number on the hurry: it told the department that expedited approval would save ratepayers approximately $17 million, on a net present value basis, in avoided Clean Peak Standard compliance costs compared with approvals in December.

Size, schedule and the rest of the docket

Energizar is 200 MWh bigger in the release than it was in front of regulators in August. In its August 6 comments to the department, Energizar described the project as "a 250 MW/1,000 MWh battery energy storage system currently in the late stages of development in Chelsea, Massachusetts," with the contracts covering 200 MW / 800 MWh of it. The project's website still lists 250 MW and 1,000 MWh. The release says 1,200 MWh and gives no megawatt figure, and neither it nor the website explains the extra 200 MWh. At 250 MW, by our arithmetic, 1,000 MWh is four hours of output and 1,200 MWh would be 4.8 (kW vs kWh covers the distinction).

The finish line has drifted too. The August comments put commercial operation in the second half of 2027 and cite contract milestones of financial close by September 30, 2026 and commercial operation by September 1, 2027, both subject to extensions Energizar can elect under the contracts. The release now says the fourth quarter of 2027. Energizar told the department in August that if it missed Eversource's spring 2027 outage window for energizing the project, energization would likely slip to fall 2027 and completion into spring 2028.

The East Coast claim is framed as of the day Energizar reaches commercial operation, and a larger project is in the same joint dockets. Jupiter Power's Trimount in Everett, which Utility Dive reported at 700 MW / 2,800 MWh, is still under review: the Attorney General filed testimony on September 9 recommending denial of its contract, and under the hearing officer's October 6 schedule initial briefs are due October 21 and reply briefs October 28, ahead of the order due by January 4. Not every Massachusetts battery gets this far: in September 2026 East Point Energy withdrew its 125 MW Tewksbury project after ISO New England's cluster study estimated $65.3 million of grid upgrades for it (East Point withdraws 125 MW Tewksbury battery over grid upgrade costs).