Adding Solar to an Existing Home: Title 24 Rules
The Energy Code neither requires solar on an existing home nor calls for a Title 24 energy report when you add it: §150.1(c)14 applies to newly constructed homes, and the Energy Commission states it does not apply to additions or alterations. The installation still needs a permit under the electrical, residential and fire provisions of Title 24, and SB 379 requires most cities and counties to offer automated online permitting for it.
- Choose your report
- Upload your plans
- Pay securely
- Permit-ready report by email
What the Energy Code requires, and when
The solar requirement in §150.1(c)14 is part of the prescriptive package for newly constructed single-family homes. The Energy Commission’s 2025 solar FAQ says it does not apply to additions, alterations to existing buildings or unconditioned buildings, and Exception 6 to §150.2(a) confirms that PV is not required for additions. The single-family alteration rules in §150.2(b) do not call for PV either. For a house that already exists, solar is voluntary as far as Part 6 is concerned.
Joint Appendix JA11, which sets orientation, shading and verification rules for PV, is scoped to systems used to meet the Standards’ prescriptive or performance requirements. A voluntary array on an existing home is not one of those, so JA11 is not the test it is checked against.
What the rest of Title 24 still requires
Title 24 is the whole building code, not only the Energy Code. Rooftop PV on any home falls under the State Fire Marshal’s provisions in Parts 2, 2.5 and 9, which the compliance manual summarises for houses: two access pathways at least 36 inches wide from the lowest roof edge to the ridge on each roof plane with an array, arrays held 18 or 36 inches below the ridge depending on how much of the roof they cover, and no array longer than 150 feet in either direction. The detail is in California Residential Code sections R324.3 and R324.6, and the electrical work follows the California Electrical Code.
How the permit works
Senate Bill 379 requires most California cities and counties to offer an online, automated permitting platform that verifies code compliance and issues permits in real time for residential solar systems up to 38.4 kilowatts AC, and for energy storage paired with them. The Energy Commission collects the compliance reports and names SolarAPP+ among the platforms in use. Jurisdictions of more than 50,000 people had to comply by 30 September 2023 and smaller cities by 30 September 2024; cities under 5,000 and counties under 150,000, with the cities in them, are exempt. Your building department will say which route it uses.
When solar does meet the Energy Code
- A new detached ADU needs PV of its own unless an exception applies. The Energy Commission allows new modules added to the main house’s existing system on the same lot to meet it, if they are part of the ADU permit; see does an ADU need solar.
- A re-roof exempts roof area under building-integrated PV from the cool roof rule of §150.2(b)1I; see re-roof Title 24.
- A battery is not required on an existing home either. JA12 sets the rules for batteries used for compliance in new construction; see JA12 battery storage.
The rules for new homes, including the system size calculation, are on is solar required on a new home.
Common Title 24 Questions
- When is Title 24 required for a home?
- Does a remodel need Title 24?
- Does a room addition need Title 24?
- What plans are needed for a residential Title 24 report?
- How much does a residential Title 24 report cost?
- How long does a residential Title 24 report take?
Frequently Asked Questions
Not under the Energy Code. The PV requirement applies to newly constructed homes. The installation needs a building permit under the electrical, residential and fire code provisions.
Automated permitting software the Energy Commission names among the platforms jurisdictions use to meet SB 379. It runs code compliance checks on eligible rooftop systems so permits can be issued in real time.
No. Exception 6 to §150.2(a) states that photovoltaic systems are not required for additions.