Your Commercial Project May Now Require Solar and a Battery. Most Owners Find Out at Plan Check.

There is a particular phone call I get a few times a year. The pro forma is set, the lender is committed, the contractor is priced. Then plan check comes back and there is a line item nobody budgeted: a photovoltaic array, and increasingly, a battery system to go with it.

It is not a small number. And it arrives at the worst possible moment, after the financing is locked and before the shovel is in the ground.

California's 2025 Energy Code expanded solar and battery storage requirements to more nonresidential buildings, and it applies to projects permitted on or after January 1, 2026. If you are scoping a commercial project right now, this belongs in your budget conversation, not your plan check conversation.

Who Is Actually Captured

Here is where I have to be careful, because there is a lot of confident misinformation on this topic.

You will see a clean "10,000 square feet" threshold quoted all over the internet. That number is a generalization. The real determination runs off occupancy type and the capacity factor tables, not a single square footage cutoff. Offices, schools, warehouses, retail, and restaurants are among the occupancies now commonly captured, but "commonly captured" is not the same as "your building is captured."

For solar, required capacity is calculated using Equation 140.10-A together with the PV capacity factors in Table 140.10-A. The 2025 cycle kept the equation itself but added occupancies to the table and changed many of the capacity factors. A building type that fell outside the requirement under the 2022 code may sit inside it now, and a system sized under the old factors may come out wrong.

For battery storage, the 2025 cycle brought more nonresidential buildings into scope and updated the capacity factors used for sizing.

The only reliable answer is a calculation on your specific building. Anyone who tells you yes or no without knowing your occupancy classification and floor area is guessing.

Mixed-Use Has Its Own Rule

Mixed-use projects are common in Central Valley infill, and they follow a distinct logic.

For solar: mixed-use buildings where 80 percent or more of the floor area is a required occupancy must install photovoltaics.

For battery storage: in mixed occupancy buildings, total required capacity is found by summing the minimum rated usable energy capacity for each required occupancy.

That summing rule matters. A project with several qualifying occupancies does not get to size to the largest one. The requirements stack.

The Costs Nobody Puts in the Early Budget

When owners budget for this, they price panels. The panels are frequently not the expensive part.

• Structural capacity. An array adds dead load and wind uplift. On a new building that is a design input. On an existing roof it can mean framing reinforcement.
• Electrical infrastructure. Interconnection, switchgear, and service capacity. A battery system needs a location that meets clearance and fire separation requirements, and that location competes with leasable area.
• Roof coordination. Mechanical equipment, skylights, and access pathways all want the same roof the array wants. Sorting this out during design is free. Sorting it out during construction is not.
• Utility timeline. Interconnection is a schedule risk that sits outside your control and outside your contractor's control.

None of this is an argument against the requirement. It is an argument for finding out early, when the array is a line on a drawing rather than a change order.

What About Exceptions

The code includes exceptions for real constraints, including limited available roof area and shading. They exist and they get used.

What they are not is a conversation you have at the counter. An exception is a technical determination that gets documented in the compliance submittal. Bringing it up for the first time when plan check flags the missing array puts you in the weakest possible position, and it costs you weeks.

Frequently Asked Questions

Does my California commercial building need solar panels?

It depends on occupancy type, building size, and permit date. The 2025 Energy Code expanded photovoltaic requirements to more nonresidential occupancies and high-rise multifamily. The determination uses the sizing equation and capacity factor tables in Section 140.10, not a single square footage number, so it has to be run for your building.

Is battery storage required on commercial buildings in California?

For a growing set of new nonresidential construction, yes. The 2025 cycle expanded battery requirements to more occupancies and updated the sizing capacity factors.

How is the required solar system size determined?

Using Equation 140.10-A with the PV capacity factors in Table 140.10-A. The 2025 cycle kept the equation but added occupancies and changed many capacity factors, so a system sized under the prior cycle may no longer be correct.

What about mixed-use buildings?

Mixed-use buildings where 80 percent or more of the floor area is a required occupancy must install solar. For battery storage, total capacity is the sum of the minimum rated usable energy capacity for each required occupancy.

Can I get an exception if my roof does not work for solar?

The code contains exceptions for constraints such as limited roof area and shading. They are technical determinations documented in the compliance submittal, and they should be evaluated during design rather than raised at plan check.

Does this apply to a tenant improvement?

These provisions are principally aimed at new construction, but the scope of work, the occupancy, and the extent of the alteration all matter. Do not assume a large TI is automatically outside the requirement.

Find Out Before Your Budget Is Locked

The worst version of this is discovering a required solar array after your financing closed. The best version is knowing during feasibility, when it is just another number in the model.

Avila Architects, Inc. runs energy code requirements during feasibility and design, not at the end. Arturo "Art" Avila is a California licensed architect, a LEED AP BD+C, a DSA-certified CASp, and a Class B General Contractor, so the compliance strategy is checked against constructability and cost from the start.

Send us your project details and we will tell you what applies.

Current as of August 2026 and based on the 2025 Building Energy Efficiency Standards, effective for projects permitted on or after January 1, 2026. Requirements depend on occupancy classification, building size, and local amendments, and code cycles change. Verify against the current code text for your specific project and jurisdiction. Reference: California Energy Commission, 2025 Building Energy Efficiency Standards. This article is professional information from design professionals, not legal advice.

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