Quick Answer: Yes — under California’s 2022 Title 24 Energy Code (effective January 2023), most new ADUs over 250 square feet require a solar photovoltaic (PV) system. The specific requirement: any new detached ADU with a conditioned floor area over 250 sq ft must install a solar PV system sized to the ADU’s projected annual energy use (typically 1.5-2.5 kW for a studio/1-BR ADU). The solar system can be installed on the ADU itself or on the main house if the capacity is sufficient. EXCEPTIONS: Attached ADUs and JADUs (junior ADUs created within the existing structure) are exempt from the solar mandate. Garage conversions may be exempt if the structure is not significantly modified. A CEPE (Certified Energy Plans Examiner) determines the exact requirement for your specific project.
California ADU Solar Requirement Summary 2025
Helpful Resources:
| ADU Type | Solar Required? | Notes |
|---|---|---|
| New detached ADU > 250 sq ft | YES | Solar PV required per Title 24 2022 code |
| New detached ADU ≤ 250 sq ft | Usually NO | Below threshold — verify with local jurisdiction |
| Attached ADU (addition to home) | Usually NO (check compliance) | Often exempt; full Title 24 report determines exact requirement |
| Garage conversion ADU | Usually NO | Existing structure conversions generally exempt |
| JADU (within existing home) | NO | Explicitly exempt under Title 24 |
| ADU above existing garage | Case-by-case | Depends on scope — requires CEPE evaluation |
The cost to add a required solar PV system to a new detached ADU in San Jose is approximately $6,000-$14,000 depending on system size. The Federal Solar Investment Tax Credit (ITC) covers 30% of this cost. Quartz Construction bundles solar coordination into our ADU design-build process — we size the system to meet Title 24 compliance and coordinate with a licensed solar installer. Learn about our ADU services. CSLB #1003436 | Call (650) 749-7436.
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