Yes. Solar is required on new homes in California. The mandate first took effect on January 1, 2020, and it continues under the 2025 Energy Code, which governs every permit application filed on or after January 1, 2026.1California Energy Commission. 2025 Building Energy Efficiency Standards If you’re building a single-family home or a low-rise multifamily building, your permit application has to include a solar photovoltaic system, and the local building department can withhold your certificate of occupancy until the system is in place.
What the Code Actually Requires
The solar requirement sits in Title 24, Part 6 of the California Code of Regulations, known as the Building Energy Efficiency Standards. The 2019 code cycle introduced mandatory solar for new low-rise residences, defined as single-family homes and multifamily buildings of three stories or fewer.2California Energy Commission. 2025 Nonresidential Solar PV That baseline carries forward under the 2025 Energy Code.1California Energy Commission. 2025 Building Energy Efficiency Standards A builder who leaves solar out of a plan set will face correction orders during plan check.
How Big a System You Need
There is no fixed kilowatt number. The required capacity depends on two things: the home’s conditioned floor area and the climate zone it sits in. California is divided into 16 climate zones reflecting different solar radiation levels and temperature patterns.3California Energy Commission. Climate Zone Tool, Maps, and Information Supporting the California Energy Code Two identical floor plans, one on the foggy coast and one in the inland desert, can end up with different required system sizes.
The Energy Code uses a formula that multiplies floor area and the number of dwelling units by climate-zone-specific factors to produce a minimum system size in kilowatts. In practice, most new single-family homes end up needing something in the range of roughly 2 to 4 kilowatts. Larger homes, or homes in hotter zones, may require more.
Exceptions That Can Get You Out of It
Not every home has to have panels. The code recognizes a short list of situations where solar would be impractical or produce little benefit.
- Heavy shading. The Solar Access Roof Area calculation excludes any roof area receiving less than 70 percent of annual solar access after accounting for neighboring buildings, hills, or large trees. If enough of the roof is shaded, the calculated system size can drop below the minimum threshold.4California Energy Commission. 2022 Single-Family Solar PV
- A very small calculated system. When the formula produces a required system smaller than 1.8 kWdc, no solar installation is required at all. This tends to affect very small homes or homes in low-demand climate zones.5California Energy Commission. 2025 Single-Family Solar PV
- Snow load. If the local enforcement authority determines the roof cannot safely support a solar array under applicable snow load requirements, the home is exempt.
These exceptions require documentation submitted during plan check. Claiming shading isn’t enough on its own. A shading study or structural assessment has to back the exemption up, and the local building department has the final say.
Community Solar as an Alternative
If rooftop solar doesn’t work for the project, there’s another path. Under Section 10-115 of the Energy Code, the California Energy Commission can approve community shared solar programs that satisfy the on-site requirement partially or fully. These are utility-scale installations whose output is allocated to individual homes through billing credits. For a program to qualify, the CEC must formally approve it, and it must deliver energy benefits at least equivalent to an on-site system. The Sacramento Municipal Utility District received CEC authorization in 2023 for its community solar compliance program.6California Energy Commission. Docket Log 22-BSTD-06 Whether this option is available to you depends on whether your local utility has an approved program.
What About Accessory Dwelling Units
ADUs are a common point of confusion. Whether one needs its own solar depends on how it’s built. A brand-new detached ADU counts as new construction under the Energy Code and has to meet the same solar PV requirements as a single-family home, sized by the same climate-zone formula.7California Energy Commission. 2025 Energy Code Accessory Dwelling Units FAQs
Converting existing space is different. Attached ADUs, garage conversions, and repurposed basements or pool houses are classified as additions or alterations, not new construction, and they do not trigger the solar mandate.7California Energy Commission. 2025 Energy Code Accessory Dwelling Units FAQs They still have to meet other efficiency requirements for the components being altered.
If you are building a detached ADU, you don’t necessarily need a second standalone system. You can add modules to the existing main-house array, as long as the additional capacity meets the code-calculated size for the ADU and the new panels are included in the ADU’s permit application.5California Energy Commission. 2025 Single-Family Solar PV That avoids a second inverter and keeps the electrical layout simpler.
Battery Storage Is Optional, but Worth Thinking About
The code does not require a battery on a new single-family home, but it strongly rewards installing one. Under the 2025 Energy Code, a builder who installs a battery energy storage system with at least 7.5 kWh of cycling capacity can reduce the required solar PV size by 25 percent.8California Energy Commission. 2025 Energy Code Chapter 7 – Renewables and Storage That reduction can meaningfully cut panel count and roof space.
Even without a battery, the home must be “battery ready,” meaning the electrical infrastructure has to include reserved space and wiring pathways so a system can be added later without a major renovation. Individual battery units are capped at 20 kWh each, with aggregate capacity limits depending on installation location: up to 80 kWh for exterior or garage installations and 40 kWh for utility closets.
The reason storage matters so much has to do with how California pays you for excess solar. In 2023, the California Public Utilities Commission replaced Net Energy Metering with the Net Billing Tariff. Under the old system, exported electricity earned credits close to the full retail rate. Under net billing, export credits reflect the grid value of the electricity at the time it’s generated, which is generally well below retail.9CPUC. Net Energy Metering and Net Billing
There’s a further wrinkle specifically for new construction. PG&E and SCE customers who voluntarily install solar and interconnect before the end of 2027 receive a temporary export compensation adder that boosts their credits for nine years. Homeowners who are required to install solar under the building code do not receive this adder.9CPUC. Net Energy Metering and Net Billing Every exported kilowatt-hour from a mandated new-construction system earns less than the same kilowatt-hour from a voluntary retrofit next door.
With a battery, you store the cheap midday surplus and use it during high-rate evening hours instead of exporting it for a fraction of what evening power costs. The CPUC has noted that homeowners can maximize savings under the net billing tariff by installing storage alongside solar.9CPUC. Net Energy Metering and Net Billing
Cost, the Federal Tax Credit, and Resale
The California Energy Commission has estimated that the solar mandate adds roughly $9,500 to the cost of building a new home. Actual costs vary with system size, labor market, and equipment. Against a California new-home price that typically runs well above $500,000, the solar component is a small share of total cost.
The federal Residential Clean Energy Credit under Section 25D of the Internal Revenue Code covers 30 percent of the cost of purchasing and installing a solar photovoltaic system, including panels, inverters, wiring, and installation labor. The credit applies to new construction, not just retrofits. It’s non-refundable, so it can reduce your federal tax bill to zero but won’t produce a refund past that point. There’s no income cap, but you need federal tax liability to use it. Any rebates or utility incentives that lower your out-of-pocket cost get subtracted before you calculate the 30 percent. The Inflation Reduction Act extended the credit through at least 2032 before it begins to phase down.10IRS. Residential Clean Energy Credit
If your builder rolls the solar cost into the purchase price of the home, you still claim the credit as the homeowner, not the builder. Ask for an itemized breakdown of the solar component so you can calculate the eligible amount accurately. Battery storage installed with the system also qualifies for the same 30 percent credit.11Office of the Law Revision Counsel. 26 USC 25D – Residential Clean Energy Credit
On resale, solar-equipped homes tend to sell at a premium. Real estate data indicates roughly a 4 percent bump on average versus comparable homes without panels, with larger premiums in areas with expensive electricity or strong solar incentives. Whether appraisers value a mandated system the same as a voluntary retrofit is still debated, but the system is unlikely to hurt resale and may help it. Plan for modest ongoing maintenance too: panel cleaning runs $150 to $300 per session, and inverters typically need replacement after 10 to 13 years at roughly $400 to $1,000 per unit.