Detached ADUs — standalone backyard units with their own roof, walls, and foundation — are the ADU type most clearly subject to California's Title 24 PV mandate. Here's exactly what's required and how to plan for it.
A detached ADU is a standalone structure not sharing walls with the primary residence. Includes ground-up custom builds, prefab/modular ADUs delivered to site, and 'tiny home' style permanent installations.
System size scales with conditioned floor area and climate zone. For a 750 sq ft detached ADU in coastal Southern California (Climate Zone 6), expect roughly 1.5 kW (5–6 panels). A 1,200 sq ft unit in Sacramento (Zone 12) typically needs 2.5–3 kW.
Detached ADU solar packages start around $7,500 cash before incentives and ~$5,250 after the 30% federal tax credit. HDM financing can drop the effective net to ~$4,500–$5,500 by passing through commercial-tier ITC.
Yes — a single combined system on either roof satisfies the combined Title 24 requirement.
Yes. Permanently installed modular and prefab ADUs are treated as new construction and require Title 24 PV.