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The U.S. power system ended 2025 with 43.6 gigawatts of utility-scale battery storage online. In just the first six months of 2026, operators added another 8.3 gigawatts, pushing total capacity to nearly 52 gigawatts. Over the prior three years, EIA data shows an annual average growth rate of 70 percent. Few segments of the energy industry are growing this fast, and few are being built on contract templates this unsettled.

That gap between deployment speed and legal infrastructure is where the real risk sits right now, for developers, for the utilities and data centers buying storage capacity, and for the lenders financing it.

What’s Actually Driving 52 Gigawatts

Storage is being built for two different reasons that happen to be converging at the same time. The first is the traditional pairing with intermittent renewables, storage smooths out solar and wind output and lets a project sell power when prices are higher rather than only when the sun happens to shine. The second, newer driver is data centers. Standalone battery projects are increasingly being sited to manage congestion and reliability challenges tied to rapid data center load growth, particularly in interconnection markets that are already constrained.

The industry expects roughly 24 gigawatts of new storage capacity in 2026 alone. A meaningful share of that is being financed and sited specifically around data center clusters, with ERCOT’s Dallas and Houston-area projects a leading example, positioned to capture both merchant revenue and behind-the-meter offtake arrangements with co-located facilities.

The Revenue Structure Isn’t the Same in Every Market

A storage contract that works in one market can be the wrong structure entirely in another, because the underlying revenue mechanics differ by region. ERCOT runs an energy-only market, so a battery there earns most of its money from arbitrage, charging when power is cheap and discharging when it’s expensive, with no guaranteed capacity payment underneath that strategy. California’s Resource Adequacy framework works differently: contracted capacity payments can represent 30 to 40 percent of a storage project’s annual revenue, a floor ERCOT projects don’t have. PJM’s recent capacity price spike signals its own acute need for dispatchable resources, changing the math again. A financing agreement or offtake contract built around one market’s structure doesn’t transfer cleanly to another.

The Regulatory Gap FERC Is Still Closing

The clearest sign that the legal framework hasn’t kept pace with deployment is a specific finding FERC made about PJM, the grid operator covering all or part of 13 states and the District of Columbia. FERC determined that PJM’s own tariff lacked sufficient rates, terms, and conditions of service governing co-located generation and load arrangements, the exact structure many storage-plus-data-center deals are built on. FERC ordered PJM to file a compliance filing by February 17, 2026, spelling out the specific terms an interconnection customer must follow to serve a co-located load, including how to designate the eligible customer that takes transmission service on the load’s behalf.

That’s a regulator telling one of the country’s largest grid operators, mid-buildout, that its existing rules don’t actually cover the arrangements companies are already signing. Storage developers and their counterparties negotiating co-location deals in PJM territory right now are working against a rulebook that was still being written as of early this year.

The FEOC Problem Nobody Priced In Two Years Ago

Foreign entity of concern restrictions now affect eligibility for the investment tax credit and the Section 45X manufacturing credit that much of the storage industry’s financing model depends on. Battery supply chains run heavily through a small number of international manufacturers, which means FEOC compliance documentation has become a real part of deal timing and cost, not a formality. Industry guidance for 2026 now treats FEOC documentation protocols as something that needs to be ready at signing, not something to work out after a customer relationship is already underway.

Companies that priced financing models two or three years ago, before FEOC rules were finalized, are discovering that the compliance framework underneath their tax credit assumptions has changed since the deal was structured. That’s the kind of gap that surfaces during due diligence on a financing round or an acquisition, not before.

What This Means for Anyone Building or Buying Storage

Four things are worth checking against current deals rather than assuming they were handled correctly when signed. Does the revenue structure match the market the project actually sits in, since an ERCOT arbitrage assumption built into a PJM capacity deal is a mismatch that eventually shows up in the financials. Do co-location and interconnection terms reflect the grid operator’s current tariff, not a template drafted before FERC forced operators like PJM to fill gaps in their own rules. Is FEOC documentation actually in place and current, given how much of the industry’s tax credit eligibility now depends on it. And have safety and siting requirements been checked against the newest state rules, since incidents at storage facilities have pushed several states toward new requirements that can affect permitting mid-project.

The Pace Isn’t Slowing Down

Nothing in the current data suggests this growth curve is flattening. Illinois enacted a wide-ranging energy law this year addressing battery storage payment structures and consumer protection requirements, one example among several states actively legislating in this space right now, and grid operators including the Southwest Power Pool have separately reformed their own interconnection queue processes to accommodate storage.

The companies moving fastest into battery storage right now are, almost by definition, moving faster than the legal and regulatory framework around them. That’s not a reason to slow down. It’s a reason to make sure the contracts, the interconnection terms, and the tax credit documentation are being built by people who are tracking where the rules actually stand today, not where they stood when storage was a much smaller part of the grid.