Is Solar Required on New Homes in California? What the 2025 Energy Code Says

What the rule requires

Section 150.1(c)14 of the 2025 Energy Code requires solar PV systems or modules for all newly constructed single-family residential buildings, with five exceptions. The CEC's guidance says the minimum system is meant to offset approximately the electricity the building would use if it were a mixed-fuel home, meaning one with a natural gas furnace, water heater, stove and clothes dryer.

Because the size is set against that mixed-fuel assumption, choosing a heat pump or electric appliances does not change the minimum PV size, according to the CEC. The things that do move it are the climate zone, the conditioned floor area, the number of dwelling units and the plug loads that raise cooling demand.

The rule dates back to the 2019 Energy Code. The CEC's 2019 training slides, effective January 1, 2020, state that all new low-rise residential buildings are to have a PV system sized to offset the annual kilowatt-hours of a mixed-fuel home. The 2025 cycle is the one that applies to permits filed from 2026.

Which new buildings are covered

The CEC lists the covered buildings as townhouses; residential buildings of occupancy group R-3 with two or fewer dwelling units; other R-3 buildings that are not multifamily buildings or hotels or motels; occupancy group R-3.1; and occupancy group U buildings on a residential site. In everyday terms that means a newly built single-family house, a duplex-size building and a townhouse.

Not covered: additions and alterations to existing buildings, and unconditioned buildings. If you are remodeling a house you already own, the new-construction solar rule does not apply to the remodel. A conditioned, newly constructed detached building on a residential lot, such as a detached accessory dwelling unit, is a different case that the CEC addresses separately. Our guide to ADU solar requirements covers it.

This page does not cover newly built apartment buildings or commercial buildings. The CEC page read for this article is about single-family buildings only, so for those building types check the CEC's own guidance for the code that applies.

How big the required system is

The CEC says the required size is the smaller of two results. The first is the solar access roof area (SARA) multiplied by 18 watts per square foot for steep-sloped roofs, or 14 watts per square foot for low-sloped roofs. The second is Equation 150.1-C, which uses the climate zone, the conditioned floor area and the number of dwelling units.

Solar access roof area is not simply the whole roof. It includes roof areas, covered parking, carports and newly constructed structures on the property that can support a PV system. It excludes roof area with less than 70 percent annual solar access after shading, roof area occupied as specified in California Building Code section 503.1.4, and roof area otherwise unavailable because of other state or local building-code requirements the CEC has confirmed.

This page does not publish a table of kilowatts by square footage. The equation's coefficients are in the Energy Code itself, and a table built from memory would be a guess. The builder's energy compliance documents state the required size for a specific plan.

A battery can shrink the required system

Adding a battery energy storage system can lower the required PV size. Under Exception 5, if the home is built with a battery that meets the CEC's Reference Joint Appendix JA12 and has a minimum cycling capacity of 7.5 kWh, the PV size from Equation 150.1-C may be reduced by 25 percent. When that exception is used, the project needs both PV and the battery.

The CEC also says a larger PV system cannot be traded for weaker efficiency measures unless a JA12-compliant battery is installed. And a builder cannot stack exceptions: the CEC's example is that Exception 2, the 1.8 kWdc threshold, cannot be combined with Exception 5, the battery reduction.

The panels do not have to go on the roof

The CEC answers directly that the PV system does not have to be on the building's roof. It can sit anywhere on the solar access roof area as the CEC defines it, including ground-mounted on the property or on top of a carport installed on the lot.

There is also a narrow alternative. When a builder uses the performance compliance approach, community solar can stand in for on-site solar if the CEC has approved a community solar program for that building type in the area. The CEC page does not say that any such program is in place for a given address, so a buyer should not assume one.

If your new home is not required to have solar

Some new single-family homes will not have a required PV system because an exception applies. The CEC also says that, for subdivisions of ten or more single-family residences where the tentative map is deemed complete or approved, newly built homes that do not need PV still have to meet solar-ready requirements under Section 110.10(b) through (e). Solar-ready means the roof and electrical design leave room for a later installation. The CEC states that this does not apply to newly constructed accessory dwelling units built on an existing lot.

Solar-ready is a design requirement, not a system. A home that is only solar-ready has no panels until someone buys them.

If you are buying a new home that has solar on it

The Energy Code requires that a system be built. The CEC pages read for this article do not say who must own the system, so whether the panels belong to the homeowner or to a third party under a lease or power purchase agreement is a question for the sales contract and the solar paperwork, not the code.

Before closing, ask for the solar documents in writing: whether the system is owned or leased, the monthly payment if there is one, who services it, and what transfer requires. If it is a lease or PPA, our solar lease buyout calculator totals the remaining payments, and our guide to what happens to a solar lease when you sell explains the transfer step. If there is a UCC-1 filing against the system, find out before escrow; the UCC-1 guide covers it.

Separately, the electric bill math for a new home with solar follows the net billing rules in force at interconnection, not the Energy Code. See the pages on how net billing works for how export credits are set.