At a glance

California's Energy Code, Title 24, Part 6, says every newly built single-family home must have a solar electric system. The California Energy Commission added the requirement in its 2019 standards, which took effect on January 1, 2020. The 2025 standards apply to homes whose building permit application is filed on or after January 1, 2026.

It applies to new construction only. The CEC said when it adopted the rule that solar for existing homes is unaffected, so adding a room or remodeling doesn't mean you have to add panels. The required systems are modest: the CEC put the typical size under the 2019 rule at 2.8 kW, against about 7.2 kW for systems homeowners added to existing homes.

How big the system must be

The code sizes the system from the home's conditioned floor area and its climate zone, with two factors from Table 150.1-C:

kW = floor area × A ÷ 1,000 + number of homes × B

Climate zone 12, 2,000 sq ft, one home: 2,000 × 0.613 ÷ 1,000 + 1 × 1.40 = 2.63 kW

A and B come from Table 150.1-C for your climate zone. The required output is the smaller of this size and your usable roof area times 18 (steep roof) or 14 (low-slope roof).

For a 2,000 square foot home, that comes to between 2.2 kW in climate zone 5 and 4.6 kW in zone 15, which has by far the biggest floor-area factor:

The roof can lower it. Only roof that can hold panels, has at least 70% of full-year sun after shading, and on a steep roof doesn't face north counts as usable, the "solar access roof area". Carports and other new structures on the lot count too. You can find your climate zone with the Energy Commission's climate zone tool.

Exceptions

  • Too little sunny roof. No system is needed if the usable roof area is under 80 contiguous square feet.
  • Tiny requirement. No system is needed if the formula gives less than 1.8 kW.
  • Snow country. No system is needed where the building department finds the panels can't meet the code's snow-load standard.
  • Older approvals. Homes approved by a planning department before January 1, 2020 with design conditions can count only the roof those conditions leave for solar.

Batteries and battery-ready wiring

A builder can make the solar system 25% smaller if the home also gets a battery of at least 7.5 kWh that meets the code's battery standard. Batteries are otherwise optional.

What isn't optional is getting ready for one. A new home with one or two units and electric service over 125 amps must be built battery-ready unless a battery is installed: backup wiring for at least 60 amps and four circuits, including the refrigerator, a light near the main exit and a bedroom outlet, or a raceway to a labeled backup subpanel; a main panel rated at least 225 amps; and space for a transfer switch within 3 feet of it.

A row of new two-story homes in wood framing and sheathing at the edge of a dry field, lit by low evening sun under a clear sky

If you buy a new home with solar

Export credits. The home goes on net billing like any other new solar home, but the CPUC says systems required by the building code don't get PG&E's or SCE's bonus export credit. See NEM 3.0 in California.

Property tax. If the builder installed the system, you as the first buyer may be able to keep it off your assessment by filing form BOE-64-SES with the county assessor. See solar and property tax.

Owned or leased. In 2019 the CEC said builders could meet the rule with leased systems as well as owned ones. Ask whether the panels come with the house or under a lease you'd take over; our lease guide covers what that means.

Next step

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Common questions

Do new homes in California have to have solar panels?

Yes. The California Energy Code requires newly built single-family homes to have a solar electric system. The rule began with the 2019 standards on January 1, 2020, and the 2025 standards, in effect since January 1, 2026, keep it.

How big does the solar system on a new California home have to be?

The 2025 code sets a minimum from the home's floor area and climate zone: floor area times a zone factor divided by 1,000, plus a per-home factor. For a 2,000 square foot home that's about 2.2 to 4.6 kW, and the code caps it by how much usable sunny roof the home has.

Does the California solar mandate apply to existing homes?

No. It's a requirement for newly constructed homes. The Energy Commission said when it adopted the rule that solar for existing homes is unaffected.

Do new California homes need a battery?

No, but a new one- or two-unit home with electric service over 125 amps must be wired battery-ready unless a battery is installed. A builder that adds a battery of at least 7.5 kWh can make the solar system 25% smaller.

Are there exceptions to California's new-home solar requirement?

Yes. No system is needed if the usable sunny roof is under 80 contiguous square feet, if the formula gives less than 1.8 kW, or where the panels can't meet the code's snow-load standard.

Building codes are enforced by your city or county building department; this is a plain-English summary of the state code, not design or legal advice. Sources: CEC: 2025 Energy Code · 2025 Energy Code, Title 24 Part 6 (restructured) · CEC: Building Energy Efficiency Standards · CEC: FAQ on the 2019 standards · CEC: climate zone tool · CPUC: net metering and net billing. Reviewed October 2026.

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