Short answer: yes — most newly constructed detached ADUs in California are required to include solar under the 2022 Title 24 Building Energy Efficiency Standards. Attached ADUs, additions, and conversions are usually exempt. Below is a plain-English breakdown of which ADUs need panels, how much solar is required, and the legal exemptions.
Title 24 Part 6 § 150.1(c)14 requires photovoltaic (PV) solar on most newly constructed low-rise residential buildings, including detached Accessory Dwelling Units. The rule applies statewide and is enforced at the local building department level when you pull a permit.
The Title 24 formula sizes your PV system based on conditioned floor area and your local climate zone. For most ADUs between 500 and 1,200 sq ft, the requirement works out to a 1.0–2.5 kW system — typically 4 to 8 panels.
Use our free Title 24 sizing calculator to get an instant kW number for your specific ADU and ZIP code.
California Energy Commission rules allow several exceptions. The most common are shading, roof area, and structural feasibility. Your designer or solar provider documents the exemption on the CF1R compliance form submitted with your permit.
No. Batteries are not required by Title 24 for ADUs, but adding one can reduce the required PV system size and significantly improve NEM 3.0 economics.
Generally no. Title 24's PV mandate applies to newly constructed buildings, and a garage conversion is treated as a remodel of an existing structure.
Yes. The PV system can be installed on the main residence's roof and counted toward the ADU requirement, as long as the total system meets the combined Title 24 sizing requirement.
Your local building department will not issue final permit sign-off (Certificate of Occupancy) without an approved Title 24 compliance form (CF1R) showing PV or a documented exemption.