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Flatiron Energy has raised $850 million to build a battery in Chelsea, Massachusetts. Six banks are named in the announcement. The two other sources of money in the package are not, and together they are the reason the headline figure is larger than the cost of the project.
Key takeaways
- Flatiron Energy secured $850 million for the Energizar battery storage project in Chelsea, Massachusetts, announced on 15 October 2026, from a consortium comprising Norddeutsche Landesbank, Santander Bank, Societe Generale, East West Bank, Investec and Siemens Financial Services.
- Energizar is a standalone utility-scale battery rated 250 MW with 1,200 MWh of storage, giving it 4.8 hours of duration, and is expected to reach commercial operations in the fourth quarter of 2027.
- The package is not a single loan. It combines construction loans, bridge facilities, term loans and letters of credit with a preferred equity commitment and an investment tax credit transfer agreement, and Leap records no split between those components.
- The preferred equity came from funds managed by an unnamed global credit manager with more than $350 billion under management, and two unnamed Fortune 500 corporations agreed to buy a portion of the investment tax credits.
- Enerdatics records 35 US battery financings of $300 million or more since the start of January 2024. Two of the 35 are in ISO-NE, and both belong to Flatiron Energy.
What is actually inside the $850 million?
Four kinds of money, which is why the total should not be read as a construction budget. The debt portion alone spans construction loans, bridge loan facilities, term loan facilities and letters of credit. A letter of credit is not cash drawn down at all. It is a bank's promise to pay a third party if the borrower fails to, and it sits in a financing package to cover obligations such as interconnection deposits and offtake security.
On top of the debt sit two instruments that are not debt. One is a preferred equity commitment, an investment that ranks ahead of ordinary equity for distributions but behind lenders in a default, and which earns a contractual return rather than a share of the upside. The other is an investment tax credit transfer, under which the project sells the federal credits it earns to a corporate buyer for cash, because the project company itself has no tax bill large enough to use them.
Leap records the total at $850 million and reports zero against every individual component, which means the split was not disclosed. That matters for anyone trying to infer a build cost. Divide $850 million by 250 MW and the answer is $3.4 million per MW. Divide it by 1,200 MWh and the answer is $708 per kWh. Both figures measure the capital raised around the project, not the capital spent on it.
Why does 4.8 hours of duration stand out?
Because duration, not power, is what a battery is paid for in a capacity-constrained urban pocket. Duration is energy capacity divided by power rating: a battery that holds 1,200 MWh and can discharge at 250 MW can sustain full output for 4.8 hours. Most US grid-scale batteries are built at two to four hours, because that is the window arbitrage and ancillary markets reward.
Energizar sits above that band, and the comparison that makes the point is almost exact. Deriva's Frontier project in Oklahoma holds 1,208 MWh, eight more than Energizar, but discharges at 302 MW rather than 250 MW. The same stored energy, spread over a smaller pipe, buys Flatiron almost an extra hour of delivery.
Location explains the choice. Chelsea sits inside greater Boston, where ISO-NE load is dense and transmission is tight, and a longer battery can cover a full evening peak rather than its sharpest hour. It also explains the capital structure: a longer asset carries more hours of contracted or quasi-contracted revenue, which is what preferred equity needs before it will price.
Has Flatiron done this before?
Thirteen months earlier, and in the same market. In September 2025 Flatiron closed $540 million in debt, preferred equity and tax credit transfer for the Taft battery project, also in ISO-NE, with First Citizens Bank, Norddeutsche Landesbank, Societe Generale, Santander Bank and Investec among the lenders. Four of those five appear again on Energizar.
So Energizar is not a new structure. It is the same three-part structure at a little over one and a half times the size, arranged with substantially the same relationship banks. That is worth more than novelty to a developer: a template that has already closed once prices faster and diligences faster the second time. Preferred equity remains rare in US renewable financings, which makes a developer using it twice in thirteen months unusual on its own.
The advisory list shows how many moving parts that template has. Orrick, Herrington & Sutcliffe and Foley Hoag advised Flatiron on legal matters, with Winston Taylor and Rath, Young and Pignatelli acting for the lenders. CCA Capital advised on the preferred equity and the tax credit transfer, Riverside Risk Advisors handled interest rate hedging, and Raymond James advised the tax credit purchasers.
Enerdatics records 125 US battery storage financings since the start of January 2024, worth $32.7 billion in total, of which 35 are $300 million or more. Energizar's $850 million ranks eleventh across that group, but most of what sits above it is a different kind of transaction: a government loan, a corporate warehouse facility, or a venture round. Measured against single-project construction packages only, Energizar is the fourth largest, behind TransGrid's Atlas VIII at about $1.17 billion, Calpine's $1 billion for a 675 MW project and Arevon's $919 million for Nighthawk.
What does the deal signal for US storage?
That the capital stack for a large battery now routinely has three layers, and only one of them is visible. Banks lend against contracted revenue, preferred equity fills the gap between what banks will lend and what sponsors will fund, and corporate tax credit buyers convert federal incentives into cash at close. The company's claim that Energizar will become the East Coast's largest battery storage project is a capacity statement. The more useful observation is that financing a project this size in New England took six banks, one credit manager and two corporate tax credit buyers.
It also shows ISO-NE catching up late and narrowly. Of the 35 large US battery financings since 2024, the overwhelming majority sit in ERCOT, CAISO and the Independent category. New England has two, both arranged by the same developer with overlapping lenders. That is a market being opened by one sponsor rather than by many, and it is why the Taft precedent matters more than the headline.
Frequently asked questions
How large is the Energizar battery project? Energizar is a standalone utility-scale battery in Chelsea, Massachusetts, rated 250 MW with 1,200 MWh of storage capacity, which gives it 4.8 hours of duration. Commercial operations are expected in the fourth quarter of 2027.
Who provided Flatiron Energy's $850 million? Norddeutsche Landesbank, Santander Bank, Societe Generale, East West Bank, Investec and Siemens Financial Services provided the bank debt. A preferred equity commitment came from funds managed by an unnamed global credit manager, and two unnamed Fortune 500 corporations are buying a portion of the investment tax credits.
Is the $850 million the cost of building Energizar? No. The figure is the total capital raised and bundles debt, letters of credit, preferred equity and proceeds from an investment tax credit transfer. Leap records no split between those components, so a build cost cannot be derived from it.
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