California’s 2025 Building Energy Efficiency Standards took effect for permit applications submitted on or after January 1, 2026, and for anyone underwriting new commercial construction in this state they changed a number that used to be small. A 4,000 square foot restaurant pad that was effectively exempt under the 2022 code now carries a 37 kW array. A 60,000 square foot hotel went from 26 kW to 114 kW — a six-figure swing in hard cost against a pro forma that was probably built on the old assumption. The code now asks more buildings for more solar and more storage, and it calculates both differently than the cycle it replaced.
The strategic point is not that compliance got more expensive. It’s that solar and storage moved from a line item you add at the end of design to a constraint that shapes the building — and that the same mandated equipment is worth very different amounts depending on when in the design process you engage with it. Here is what Section 140.10 actually requires, how to run the numbers for your occupancy and climate zone, which exceptions are worth designing toward, and the CALGreen EV trigger that catches more budgets than any other line in the code.
What the 2025 code actually changed
The 2025 Energy Code (Title 24, Part 6) is the fourth consecutive cycle to expand on-site generation requirements, and the first to make batteries a genuinely universal condition of building commercial property in California. The trigger is the permit application date, not the construction start: applications submitted on or after January 1, 2026 are subject to the new standards. Projects that got a complete application in before the deadline remain under the 2022 code.
Three structural changes matter more than any individual number.
Climate zone granularity went from three groups to sixteen. The 2022 code grouped California’s sixteen climate zones into three buckets for PV sizing. The 2025 tables assign a distinct capacity factor to every climate zone. Marin County spans Climate Zones 2 and 3, and the difference is no longer academic — a library in CZ 2 carries a 3.23 W/ft² factor against 2.59 in CZ 3, a 25% swing on the same building.
The occupancy list expanded and fragmented. The 2025 code added Events & Exhibits, Religious Worship, and Sports & Recreation as regulated building types, and removed laboratories from the exempt list. More consequentially, it broke apart the 2022 code’s catch-all category — the bucket that had lumped auditoriums, hotels, libraries, medical offices, restaurants, and theaters together at a uniform 0.39–0.58 W/ft². Each of those uses now has its own factor, and several of them are dramatically higher.
Battery sizing was decoupled from array sizing. Under the 2022 code you computed the PV requirement, then multiplied it by a storage-to-PV ratio. The 2025 code gives batteries their own capacity factor in watt-hours per square foot of conditioned floor area, calculated independently. The practical consequence shows up in every project where roof area constrains the array — more on that below.
Calculating the PV requirement: Equation 140.10-A and the SARA cap
Section 140.10(a) applies to all newly constructed buildings of the listed types, and to mixed-occupancy buildings where at least 80% of the floor area serves one or more of those types. The base calculation is straightforward:
kWPVdc = (CFA × A) ÷ 1,000, where CFA is conditioned floor area in square feet and A is the PV capacity factor from Table 140.10-A for your building type and climate zone.
A 40,000 square foot office building in Climate Zone 2 — much of inland Marin, Sonoma, and the East Bay — carries a factor of 3.13 W/ft², producing a 125 kWdc requirement. The same building in Climate Zone 3, covering coastal Marin and San Francisco, uses 2.59 W/ft² for 104 kWdc. In mixed-occupancy buildings you run the equation against each occupancy’s floor area separately and sum the results.
The second half of the requirement is the ceiling. The code takes the smaller of the equation result and the capacity supportable by your Solar Access Roof Area (SARA) — total available SARA multiplied by 18 W/ft² for steep-sloped roofs or 14 W/ft² for low-sloped roofs. SARA is not gross roof area. It excludes any area with less than 70% annual solar access after shading, occupied roofs under CBC Section 503.1.4, and roof area unavailable because of other code requirements. It includes covered parking, carports, and other new site structures capable of supporting PV.
SARA is a design decision, not a reporting exercise
Mechanical equipment placement, parapet heights, and skylight layout all move the SARA number, and the SARA number can cap your obligation. On roof-constrained projects, a genuine shading analysis done during design development is worth more than the same analysis done at plan check — because by plan check the equipment layout is frozen and the array is whatever’s left.
The battery requirement is no longer a ratio to your array
Every building required to install PV under 140.10(a) is also required to install a battery energy storage system under 140.10(b), qualified to Reference Joint Appendix JA12. The minimum rated usable energy capacity is:
kWhbatt = (CFA × B) ÷ (1,000 × √C), where B is the BESS capacity factor from Table 140.10-B in Wh/ft² and C is the rated single-cycle AC-to-AC round-trip efficiency of the system.
Two features of this equation are worth pausing on.
Round-trip efficiency sits in the denominator, under a square root. A system at the JA12 floor of 80% round-trip efficiency requires roughly 5% more nameplate capacity than one at 88% to satisfy the same building. On a 220 kWh requirement that is about 11 kWh of hardware — a real number, and one of the few places in the code where specifying better equipment reduces the quantity you have to buy.
Power capacity is now fixed at a four-hour duration. The 2022 code set inverter power with a separate table factor. The 2025 code simply divides: kWbatt = kWhbatt ÷ 4. That 40,000 sf CZ 2 office needs roughly 224 kWh of usable capacity at 88% round-trip efficiency, and 56 kW of rated power to go with it.
For office occupancies the arithmetic happens to land in the same place as the old method — 5.26 Wh/ft² divided by 3.13 W/ft² is 1.68 Wh/W, exactly the 2022 storage-to-PV ratio. But the decoupling matters wherever SARA caps the array. If your PV is limited by available roof, Equation 140.10-C prorates the battery by the ratio of SARA-limited capacity to the uncapped requirement. Retail and grocery are the clearest case of genuine change: the PV factor rose about 20% in CZ 2 while the effective storage-to-PV ratio fell by roughly half, from 1.03 to about 0.52 Wh/W.
What JA12 actually demands of the equipment
A battery only counts if it is JA12-qualified and certified to the California Energy Commission by the manufacturer. JA12 requires UL 1973 and UL 9540 testing (with inverters to UL 1741 and UL 1741 Supplement A), at least 5 kWh of usable capacity, at least 80% round-trip efficiency, and warranted retention of 70% of nameplate capacity after 4,000 cycles or under a 10-year warranty. It also requires the system to switch between multiple control strategies — Basic, Time-of-Use, and Advanced Demand Response.
That last requirement is the most commonly overlooked, and from an owner’s perspective it is the most valuable line in the section. The code is not mandating a compliance box; it is mandating a battery that can be dispatched against a rate schedule. Whether that asset earns anything depends entirely on whether anyone configures it to — which is the argument we make in The Hidden ROI of Commercial Batteries.
Which occupancies got expensive
Three numbers to carry into a pro forma
21× — the increase in the required PV capacity factor for restaurants in Climate Zone 2 (0.44 → 9.32 W/ft²). 4 hours — the battery duration now fixed by code; rated power is simply usable capacity divided by four. 10 kWh — the computed threshold below which no battery system is required, regardless of occupancy.
The table below compares Climate Zone 2 capacity factors across the two code cycles. Climate Zone 2 covers inland Marin and much of the North Bay; CZ 3 factors run modestly lower.
| Building type | 2022 code (W/ft²) | 2025 code (W/ft²) | Change |
|---|---|---|---|
| Restaurant | 0.44 | 9.32 | 21× |
| Library | 0.44 | 3.23 | 7.3× |
| Medical office / clinic | 0.44 | 3.13 | 7.1× |
| Hotel / motel | 0.44 | 1.90 | 4.3× |
| Retail / grocery | 2.91 | 3.49 | +20% |
| Office / financial | 3.13 | 3.13 | No change |
| High-rise multifamily | 2.21 | 2.21 | No change |
| School | 1.63 | 1.63 | No change |
| Warehouse | 0.44 | 0.44 | No change |
| Religious worship | — | 4.65 | New |
| Events & exhibits | — | 4.28 | New |
| Sports & recreation | — | 1.97 | New |
The restaurant number deserves a worked example, because it inverts the usual assumption that small buildings escape the mandate. A 4,000 square foot restaurant in CZ 2 previously computed to 1.8 kW — below the 4 kW threshold, and therefore exempt. Under the 2025 factors the same building computes to 37.3 kW. If rooftop equipment leaves only 2,000 square feet of qualifying low-sloped SARA, the requirement caps at 28 kW (2,000 × 14 W/ft²), and the battery prorates accordingly — roughly 13 kWh, still above the 10 kWh exception. A quick-service pad building went from having no solar obligation to carrying a meaningful array and a battery.
Hotels tell a similar story at scale. A 60,000 square foot hotel in CZ 2 moves from 26 kW under the old catch-all factor to 114 kW under the 2025 tables, with about 54 kWh of storage attached. For a hospitality developer running pro formas built on 2022 assumptions, that is a six-figure swing in hard cost that has to be found somewhere — and it is far cheaper to find it at schematic design than at plan check.
The exceptions worth designing toward
Section 140.10 contains eight exceptions across the PV and battery requirements. Most are narrow. Four are worth understanding before schematic design is complete.
The small-system floors. No PV is required where total SARA is less than 3% of conditioned floor area, where the computed PV requirement is under 4 kWdc, or where SARA contains less than 80 contiguous square feet. On the battery side, no BESS is required if the computed usable capacity is under 10 kWh, or if the installed PV is less than 15% of the Equation 140.10-A capacity.
The multitenant square-footage carve-outs. For nonresidential and hotel/motel multitenant buildings, PV capacity is calculated excluding tenant spaces that meet all three of: 2,000 square feet or less of conditioned space, served by an HVAC system dedicated to that space, and individually metered. On the battery side, capacity is based only on tenant spaces exceeding 5,000 square feet — and a single-tenant building under 5,000 square feet needs no battery at all. On small-bay retail and flex projects, tenant demising and HVAC zoning decisions made for leasing reasons now have direct code consequences.
The carve-out disappears if you plan to share the solar
The multitenant PV exception does not apply where the Commission has approved a community solar program for compliance under Title 24, Part 1, Section 10-115, or where the load-serving entity offers virtual bill credits to nonresidential and hotel/motel tenants. In other words: if your plan is to allocate one array’s output across tenant meters — the Virtual Net Billing Tariff arrangement covered in our multi-tenant NEM billing analysis — you cannot also shrink the required array by excluding those tenants. Pick one, deliberately, at design stage.
Snow load. Buildings where the enforcement authority determines a PV system cannot meet ASCE 7-16 Chapter 7 snow loads are exempt. Relevant to the Sierra, not to Marin.
Worth noting what Section 140.10 does not reach: it applies to newly constructed buildings. Additions, alterations, and repairs to existing nonresidential buildings are governed by Section 141.0, which as a general matter does not carry the PV and battery mandate. If you are re-roofing, retenanting, or expanding an existing property, confirm scope with your AHJ — but the mandate is a new-construction condition, not a retrofit trigger.
The CALGreen EV trigger nobody budgets for
The most expensive surprise in the 2025 code cycle is not in Part 6 at all. It is in CALGreen (Part 11), and it fires on existing sites.
New construction EV requirements tightened: Table 5.106.5.3.1 added a separate, higher column for office and retail occupancies. A 40-space office project now requires six EV charging stations plus two EV-capable spaces, against four EVCS for other occupancies at the same count. Above 200 spaces, office and retail must build EVCS at 75% of EV-capable spaces — where EV-capable spaces are themselves 20% of actual parking. Level 2 (208/240V, 40A) is the reference station; low-power Level 2 at 20A counts as half a station, DC fast charging counts as five, and at least one true Level 2 charger is always required.
The trigger that catches owners is on the alteration side. Parking lot work pulls in EV infrastructure requirements when parking area is added, when electrical work requires trenching, and — critically — when a new photovoltaic system is installed covering existing spaces. Restriping alone does not trigger anything. But a solar carport over an existing lot does, for the spaces under the canopy. If those spaces already have EV-capable infrastructure, they must be upgraded to functioning charging stations.
This is a genuine coupling, and it cuts both ways. A carport is often the cleanest way to add SARA on a roof-constrained site — covered parking counts toward SARA under 140.10(a). But pricing a canopy without pricing the EVCS build-out underneath it produces a number that will not survive plan check. We scope these together for exactly that reason: the trenching, service capacity, and panel work the canopy requires is largely the same trenching, service capacity, and panel work the chargers require, and doing them in one mobilization is materially cheaper than discovering the requirement at permit and returning to the site. The scoping questions are the same ones we walk through in EV charging for commercial facilities.
Certain occupancies — grocery, manufacturing, office, retail, and warehouse — also carry medium- and heavy-duty EV charging readiness requirements where off-street loading spaces are provided, meaning additional raceway, transformer, and panel capacity reserved for future truck charging. That provision did not change in 2025, but it was expanded in the July 2024 intervening cycle and is still catching projects.
Practical takeaways for owners and GCs
If you are permitting new commercial construction in California right now, this sequence keeps the energy scope from becoming a change order:
- Run Equation 140.10-A against your actual occupancy mix and climate zone at schematic design — not at plan check. Mixed-occupancy buildings sum the requirement across each use, and the answer drives structural, electrical, and roof layout decisions that are expensive to revisit.
- Do a real SARA analysis before freezing the roof plan. SARA can cap your obligation, and the 70% annual solar access threshold means equipment placement and parapet design directly change the number.
- Specify round-trip efficiency, not just capacity. An 88% system needs about 5% less nameplate than an 80% system for the same building, and the JA12 control-strategy requirement means the battery has to be dispatchable regardless.
- Decide the multitenant question once. Either use the small-tenant carve-out to reduce the array, or plan to allocate output across tenant meters — you cannot do both.
- Price solar canopies and EV charging as one scope. A PV canopy over existing parking triggers CALGreen EVCS requirements for the covered spaces. Budget them together or the canopy number is fiction.
- Check for local reach codes. Cities and counties may adopt amendments exceeding Title 24 after filing with the CEC. Marin jurisdictions have historically been active here.
- Confirm your federal tax position early. Commercial solar projects that began construction on or before July 4, 2026 may extend their placed-in-service window under the continuity safe harbor; projects beginning after that date generally must be placed in service by December 31, 2027 to claim the credit. Standalone battery storage remains eligible under 48E through 2032 on its own timeline. The code will require the array either way — whether it comes with a tax credit attached is now a scheduling question, and one we walk through in the July 4 deadline piece. Verify specifics with tax counsel.
The through-line across all seven: the 2025 code moved solar and storage from a line item you add at the end of design to a constraint that shapes the building. Treated as an afterthought, it produces undersized service, awkward equipment yards, and a battery bought to satisfy an inspector. Treated as a design input, the same mandated equipment does real work — demand-charge management, time-of-use arbitrage, and backup capacity a tenant will pay for.
You are going to buy the array and the battery either way. The only decision left is whether they show up in the model as a cost of permitting or as an asset with a return — and that decision gets made at schematic design, not at plan check.
This article is general information, not legal, tax, or code-compliance advice. Capacity factors and exceptions cited are from the 2025 California Energy Code, Title 24 Part 6, Section 140.10 and Tables 140.10-A and 140.10-B. Confirm current requirements with your design team, your authority having jurisdiction, and the California Energy Commission — and your federal tax position with tax counsel — before relying on them.