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ADU Electrical Requirements in California: Panels, Feeders and Circuits
Accessory dwelling units are the fastest-growing type of new construction in California, and electrical is where many projects stall. The question is almost always the same: can the existing service support a second dwelling? Here is how to plan it right with a new construction electrician.
Start with a load calculation
Before drawing anything, an electrician calculates the combined demand of the main house and the ADU. A 100 amp service rarely supports both. Most projects either upgrade to 200 amps or install a separate service for the ADU. Our panel upgrade page explains the options.
Sub panel and feeder
An ADU normally gets its own sub panel, fed from the main panel by an underground or overhead feeder sized for the ADU's load. Detached ADUs need their own grounding electrode and a disconnect at the building.
Required circuits inside the ADU
- Two 20 amp small appliance circuits for the kitchen
- Dedicated circuits for range, microwave, dishwasher and refrigerator as applicable
- A 20 amp bathroom circuit
- A laundry circuit if a washer is included
- HVAC or mini split circuit
- Water heater circuit, often 240V for heat pump units
- Lighting and general receptacle circuits with AFCI and GFCI protection
EV-ready and solar-ready
California building code requires many new dwellings to be EV-ready and solar-ready. Plan an EV charger circuit or raceway and leave panel capacity for solar. It is far cheaper during construction than after.
Garage conversions
Converting a garage to an ADU usually means the existing garage circuit is nowhere near enough. Expect a new sub panel and a complete rewire of the space, plus interconnected smoke and CO detectors.
Permits and inspections
ADU electrical is inspected at rough and final. We coordinate both and work from your plans to give you a bid. We wire ADUs throughout California, including Los Angeles, San Jose, Oakland and Sacramento. Call (888) 633-7804 to get started.