California’s Title 24 solar requirements, set out in Part 6 of the Building Energy Efficiency Standards, require a photovoltaic system on nearly every new building in the state. The 2025 edition, developed by the California Energy Commission, took effect January 1, 2026, and applies to any project whose permit application is submitted on or after that date.1California Energy Commission. 2025 Building Energy Efficiency Standards The code sets a minimum PV size, adds battery-storage rules, lists a short set of exceptions, and requires three compliance certificates before a building can pass final inspection.
Which New Buildings Are Covered
On the residential side, the mandate applies to all newly constructed single-family homes (including townhouses), low-rise and high-rise multifamily buildings, and hotel or motel occupancies.2California Energy Commission. 2025 Single-Family Solar PV For non-residential projects, the rule kicks in when at least 80 percent of a building’s total floor area falls within covered types: offices, retail, schools, grocery stores, warehouses, restaurants, hotels, libraries, and medical offices.3California Energy Commission. 2022 Nonresidential Solar PV
One boundary trips up a lot of homeowners. Additions and alterations to existing buildings do not trigger the solar mandate. Adding a room, converting a garage into an ADU, or gutting a kitchen doesn’t put you under these rules. The requirement applies only to ground-up new construction, or to projects where an existing building was fully demolished first.2California Energy Commission. 2025 Single-Family Solar PV
How the Required System Size Is Calculated
There is no fixed panel count or flat wattage. For single-family homes, the minimum PV size comes from Equation 150.1-C, which factors in the climate zone, the conditioned floor area, and the number of dwelling units.2California Energy Commission. 2025 Single-Family Solar PV California has 16 climate zones, so a home in foggy San Francisco carries a different adjustment factor than one in Palm Springs.
The equation produces a number in kilowatts DC, but that number doesn’t stand alone. The code also calculates the maximum PV capacity that fits on the building’s Solar Access Roof Area (SARA), and the builder installs whichever is smaller. SARA is the usable roof space where panels can realistically produce power, including the main roof, covered parking, carports, and other new structures capable of supporting panels.4California Energy Commission. 2022 Single-Family Solar PV Roof areas with less than 70 percent annual solar access, because of trees, hills, or neighboring buildings, are excluded. The code then converts SARA to a capacity cap using 18 watts per square foot for steep-sloped roofs and 14 watts per square foot for low-sloped roofs.2California Energy Commission. 2025 Single-Family Solar PV
Battery Storage Rules
For newly built single-family homes with one or two dwelling units, the code requires the building to be “Energy Storage System Ready.” The builder installs the electrical infrastructure needed for a future battery, including dedicated branch circuits, adequate panel capacity, and reserved space for connection equipment, but doesn’t have to install the battery itself.5California Energy Commission. 2022 Single-Family Electric Ready
A builder who voluntarily installs a battery meeting Reference Joint Appendix JA12 gets something back: the minimum PV size from Equation 150.1-C drops by 25 percent. The battery must have a minimum cycling capacity of 7.5 kWh to qualify.2California Energy Commission. 2025 Single-Family Solar PV A compliant battery also generates a self-utilization credit against the home’s overall energy efficiency requirement, giving builders more flexibility in meeting the code’s performance targets.
There is a catch. The 25-percent battery reduction cannot be combined with the small-system exception below 1.8 kWdc. If a builder uses the battery reduction to shrink the required system, both the panels and the battery have to actually be installed.2California Energy Commission. 2025 Single-Family Solar PV
Non-residential buildings and high-rise multifamily projects are treated more prescriptively. Battery size is tied directly to installed PV capacity, using equations that factor in the solar system’s output and a battery power capacity factor specific to the building type.3California Energy Commission. 2022 Nonresidential Solar PV
Exceptions to the Solar Mandate
Section 150.1(c)14 of the 2025 Energy Code lists the situations where no PV system is required:
- SARA is less than 80 contiguous square feet.
- The Equation 150.1-C calculation produces a minimum system below 1.8 kWdc.
- The local enforcement authority determines the installation cannot meet snow load requirements under ASCE 7-16, Chapter 7.
- The building was approved by the local planning department before January 1, 2020, with mandatory conditions of approval already in place.
The shading rule inside the SARA definition also works as a practical exemption. If a building’s entire roof gets less than 70 percent annual solar access, SARA drops to zero and no system is required.2California Energy Commission. 2025 Single-Family Solar PV
Community Solar as an Alternative
When on-site installation isn’t workable, the code offers a substitute path: subscribing the building to a community solar program. This route is available through the performance compliance approach, but only if the California Energy Commission has formally approved a community solar program for that building type in that location under Section 10-115.6California Energy Commission. 2025 Nonresidential Solar PV Approval is both location-specific and building-type-specific, so verify program availability early rather than assuming it will be there.
Documents You Need to File
Three certificates prove compliance, each at a different stage. Missing any of them can hold up final inspection.
Certificate of Compliance (CF-1R)
The CF-1R is the design-stage document. It lays out the building’s proposed energy features and PV sizing, and it must be registered with an approved energy compliance provider before the building department will accept a permit application on projects that require field verification.7California Energy Commission. 2025 Energy Code Compliance Documents – Forms for Single-Family Buildings Simpler projects without field verification can use a downloadable version.
Certificate of Installation (CF-2R)
The CF-2R is completed after the solar and any battery components are installed. The installer confirms the equipment was put in as designed and matches the CF-1R specifications.7California Energy Commission. 2025 Energy Code Compliance Documents – Forms for Single-Family Buildings
Certificate of Verification (CF-3R)
The CF-3R is the final check. A certified Home Energy Rating System (HERS) rater performs independent field verification confirming the installed system meets all performance and installation standards. The local building department will not sign off on final inspection without a completed CF-3R on file.7California Energy Commission. 2025 Energy Code Compliance Documents – Forms for Single-Family Buildings
What Changed With the 2025 Edition
The 2025 code builds on the 2022 framework but shifts the incentive structure around batteries. Under the 2022 code, installing a battery was purely voluntary for single-family homes. The 2025 code keeps the voluntary framing but adds weight: a JA12-compliant battery now generates a self-utilization credit against the home’s efficiency requirement, on top of the 25-percent PV size reduction.2California Energy Commission. 2025 Single-Family Solar PV
The 2025 edition also blocks two workarounds. Builders can’t stack the small-system exception (below 1.8 kWdc) with the 25-percent battery reduction, and a larger solar array cannot substitute for less-efficient building components unless a JA12-compliant battery is also installed. Both changes push new construction toward genuine efficiency rather than oversized panels standing in for a tighter envelope.