California Just Mandated Battery Storage in Commercial Buildings

California Assembly Bill 1373, signed on February 7, 2026, requires every commercial building over 50,000 square feet in the state to install battery energy storage by January 1, 2029. The minimum capacity is set at two hours of average peak demand. Indoor installations must carry UL 9540A certification. CalFire is developing a fast-track permitting process for indoor BESS, expected by Q3 2026.

The bill covers an estimated 47,000 buildings statewide. It is the first law in the United States that mandates battery storage in existing commercial buildings.

Why a mandate. California has spent the past decade building incentive programs for commercial storage. SGIP, the Self-Generation Incentive Program, offered per-kilowatt-hour rebates. Demand charge rates created economic signals. Title 24 efficiency standards nudged new construction toward storage-ready designs. The state has more commercial battery installations than any other.

None of it was fast enough. California curtailed 3.6 million megawatt-hours of renewable energy in 2024 — enough to power half a million homes — because midday solar generation exceeded demand and the grid had nowhere to put the excess. Evening peaks still strain generation capacity. Utility-scale storage projects face multi-year interconnection queues. The distributed, behind-the-meter fleet that could absorb midday solar and discharge during evening peaks has grown steadily, but not at the pace the grid requires.

AB 1373 replaces the incentive approach with a compliance approach. Building owners do not choose whether to install storage. They choose when and from whom.

The specifics. The two-hour minimum capacity requirement is tied to a building’s average peak demand, not its maximum. For a commercial office building with 400 kW average peak demand, the mandate requires 800 kWh of installed storage. For a large retail location with 200 kW average peak, the requirement is 400 kWh.

Buildings in disadvantaged communities and those eligible for SGIP equity budgets receive an 18-month extension, pushing their compliance deadline to July 1, 2030. The extension acknowledges that building owners in under-resourced areas may face financing and procurement challenges that their counterparts in wealthier districts do not.

The UL 9540A indoor certification requirement is significant. It limits the field of eligible products to those that have completed rigorous fire safety testing for indoor installation — a subset of the broader market. For manufacturers that already hold UL 9540A certification, the mandate creates a captive market of 47,000 buildings. For those that do not, it creates a deadline to obtain certification or cede the California market.

The same week. AB 1373 did not arrive in isolation. During the same week:

Eversource Energy filed a petition with the Massachusetts Department of Public Utilities proposing a 1.2 GW behind-the-meter commercial storage aggregation program. The utility would provide zero-cost turnkey installations to C&I customers with demand above 200 kW, in exchange for 15-year dispatch rights during ISO-NE peak events. Guaranteed customer bill savings: 25 percent on demand charges. Capital commitment: $1.8 billion through 2030.

Commonwealth Edison filed revised commercial time-of-use rates with the Illinois Commerce Commission introducing a 300 percent peak-to-off-peak differential — $0.27 per kWh peak versus $0.09 off-peak — the widest spread among Midwest utilities. ComEd projects 400 MW of commercial BTM storage deployment by 2028 under the new rate structure.

PSE&G submitted a $2.3 billion infrastructure investment plan to the New Jersey BPU, including a 500 MW commercial storage aggregation pilot offering zero-upfront-cost installations in exchange for utility dispatch rights during PJM capacity events.

NYSERDA announced the Inclusive Solar and Storage Incentive program, a $400 million initiative with base incentives of $350 per kWh and up to $600 per kWh for projects in Environmental Justice areas. Storage-only projects are eligible for the first time.

The pattern. California mandated it. Massachusetts and New Jersey are financing it. Illinois restructured rates to incentivize it. New York increased subsidies for it. These are five of the six largest commercial electricity markets in the country, and in a single week, each advanced a distinct policy mechanism to accelerate commercial battery storage deployment.

The mechanisms are different. Mandates, utility programs, rate redesign, and incentives each operate through different channels and on different timelines. But they share a common premise: the voluntary pace of commercial storage adoption is insufficient for grid needs, and policy intervention is required to close the gap.

What changes. For commercial building owners in California, AB 1373 converts storage from a financial optimization to a building code requirement. The calculation is no longer whether storage pencils out, but which system meets compliance at lowest total cost. That shift in framing compresses procurement timelines and favors established products with clear certification paths.

For the broader industry, the question is whether California’s mandate becomes a template. Building energy codes have historically diffused from California to other states over 5- to 10-year cycles. Title 24 efficiency standards were adopted by dozens of states. If AB 1373 follows the same pattern, commercial storage mandates could become a standard feature of building codes nationwide within a decade.

The 47,000 buildings covered by AB 1373 represent immediate demand. The policy precedent it establishes may represent something larger.

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