Solar is required in California on most newly constructed buildings, but not on existing ones. Since January 1, 2020, nearly all new single-family homes and low-rise multi-family buildings must include a rooftop solar photovoltaic system, and since January 1, 2023, the requirement has extended to most new commercial buildings and high-rise residential buildings, which must also include battery storage. If your home or building already exists, you are not required to add solar.
New Homes Built on or After January 1, 2020
California’s Energy Code (Title 24, Part 6 of the Building Standards Code) requires solar PV systems on almost all newly constructed single-family houses, townhouses, duplexes, and low-rise apartment or condo buildings up to three stories.1California Energy Commission. 2022 Single-Family Solar PV
The required system size isn’t a single number. It is calculated two ways, and the builder installs whichever is smaller: the largest system that physically fits on the usable roof area, or a formula based on the home’s climate zone, conditioned floor area, and number of dwelling units. The target is to offset the building’s estimated annual electrical use as if it ran on a mix of gas and electric appliances. Electric heat pump heating and water heating do not increase the required system size.1California Energy Commission. 2022 Single-Family Solar PV
Battery storage isn’t mandatory for homes, but installing a system with at least 7.5 kWh of usable capacity lets the builder cut the required solar size by 25 percent.1California Energy Commission. 2022 Single-Family Solar PV
New Commercial and High-Rise Buildings Built on or After January 1, 2023
The mandate expanded on January 1, 2023, to newly constructed nonresidential buildings and multi-family buildings taller than three stories. Offices, retail stores, grocery stores, restaurants, hotels, schools, hospitals, and warehouses are all covered.2California Energy Commission. 2025 Nonresidential Solar PV
For these buildings, battery storage is required alongside the solar panels. Solar capacity is set by the building’s conditioned floor area and building type using sizing tables in the Energy Code, and the battery is then sized to the solar system.3California Energy Commission. 2025 Nonresidential Battery Energy Storage System (BESS)
Existing Buildings, Additions, and Alterations
If your home or commercial building already exists, California does not require you to install solar. The mandate applies only to new construction. Additions and alterations to existing buildings are also excluded from the solar requirement.1California Energy Commission. 2022 Single-Family Solar PV Some local jurisdictions may adopt stricter rules that reach existing structures, but there is no statewide requirement to retrofit.
Exemptions From the Solar Mandate
Even for new construction, several situations remove or replace the requirement.
Residential Exemptions
- The Solar Access Roof Area (SARA) is less than 80 contiguous square feet. Roof areas facing within 90 degrees of true north are excluded from this calculation on steep-sloped roofs.
- Roof areas with less than 70 percent annual solar access due to shading from trees, hills, or neighboring structures are excluded from usable roof area, and the remaining usable area falls below the 80-square-foot threshold.1California Energy Commission. 2022 Single-Family Solar PV
- The calculated minimum system size is less than 1.8 kW.
- The local enforcement authority determines the system cannot meet structural snow load standards.
- The building was approved by the local planning department before January 1, 2020, with mandatory conditions of approval in place.
Nonresidential Exemptions
Solar is not required on a new commercial building when the total usable roof area is less than 3 percent of the conditioned floor area, when the minimum calculated system capacity is less than 4 kW, or when usable roof area is under 80 contiguous square feet.2California Energy Commission. 2025 Nonresidential Solar PV The snow load exception also applies. Multi-tenant buildings can exclude individual tenant spaces of 2,000 square feet or less that have their own HVAC system and utility meter.
For the battery requirement, three exceptions apply: buildings where the installed solar system is less than 15 percent of the calculated capacity, buildings where the calculated battery capacity is under 10 kWh, and single-tenant buildings with less than 5,000 square feet of conditioned floor area.3California Energy Commission. 2025 Nonresidential Battery Energy Storage System (BESS)
Community Solar as an Alternative
Participation in a California Energy Commission-approved community shared solar program can substitute for on-site panels. This is an alternative compliance path, not a true exemption. The CEC must have approved a program for the building type and geographic area, and approved programs are limited. The Sacramento Municipal Utility District runs one of the few active programs for new low-rise residential construction in its service territory.1California Energy Commission. 2022 Single-Family Solar PV
Rebuilding After a Natural Disaster
In July 2025, the Governor issued an executive order creating a narrow exemption for homes substantially damaged or destroyed by natural disasters like wildfires or earthquakes. Homeowners rebuilding these properties are not required to install solar or battery storage, but the rebuilt structure must be “solar ready,” meaning wired and structurally prepared for a future installation.4Office of the Governor. Executive Order – Rebuilding Streamlining
Can an HOA Stop You From Installing Solar?
If you own an existing home and want to add solar voluntarily, the state protects that right. California’s Solar Rights Act, codified at Civil Code Section 714, makes any HOA rule or CC&R provision void and unenforceable if it would significantly increase the cost of a solar system or significantly decrease its efficiency.5California Legislative Information. California Code CIV Division 2 Part 1 Title 2 Chapter 2 Article 2 Section 714
The statute puts numbers on “significantly.” For rooftop solar electric systems, an HOA restriction is unreasonable if it would add more than $1,000 to system cost or reduce efficiency by more than 10 percent. When a homeowner submits a solar installation request, the HOA must treat it like any other architectural modification request and cannot willfully delay or avoid a decision.5California Legislative Information. California Code CIV Division 2 Part 1 Title 2 Chapter 2 Article 2 Section 714 An HOA can still set reasonable aesthetic guidelines, such as requiring panels to match the roof pitch, but it cannot demand changes that would meaningfully shrink or handicap the system.
What a Code-Mandated System Means for Your Utility Bill
If you buy a new home with a required solar system, excess daytime generation flows to the grid for bill credits. Since April 15, 2023, new solar customers of PG&E, SCE, and SDG&E are placed on the Net Billing Tariff. Export credits are based on the value the generation provides to the grid at the time it is produced, not the retail rate you pay for power. Those credits are usually lower than retail, though they can exceed retail during late summer evenings when demand peaks. Credits roll over monthly until an annual true-up, when any remaining net surplus is compensated at the wholesale energy price.6California Public Utilities Commission. Net Energy Metering and Net Billing
One point specific to new construction: residential PG&E and SCE customers who interconnect before the end of 2027 receive slightly higher export credits for nine years, but customers whose solar was required by the building code do not qualify for that adder.6California Public Utilities Commission. Net Energy Metering and Net Billing If you are buying a new home in California, this is worth factoring into any savings estimate the builder gives you.