What are the basic electrical requirements for any ADU in California?

Every California ADU must be wired to the current California Electrical Code (the CEC, which adopts the NEC with California amendments) and the Title 24 energy standards. At a minimum that means a properly sized panel or subpanel, code-mandated circuits, GFCI and AFCI protection, smoke and CO detection, and EV-ready infrastructure — all documented on a stamped or signed plan set the building department can plan-check.

The non-negotiable baseline

Regardless of whether your ADU is a new detached unit, an attached addition, or a garage conversion, these elements appear on nearly every compliant electrical plan set:

• A dedicated panel or subpanel sized by a formal NEC Article 220 load calculation — never a rule of thumb.
• Two 20-amp small-appliance circuits serving the kitchen countertop receptacles, plus a dedicated 20-amp laundry circuit and a dedicated bathroom receptacle circuit.
• GFCI protection at all kitchen countertop outlets, bathroom outlets, garage and outdoor receptacles, and anything within 6 feet of a sink.
• AFCI protection on 120V branch circuits serving sleeping rooms and most habitable spaces.
• Dedicated circuits for fixed appliances — range/cooktop, water heater, HVAC, dishwasher, and washer/dryer.
• Smoke alarms and carbon monoxide alarms in code-required locations (interconnected where required).
• EV-ready conduit and a reserved breaker space from the panel to a designated charging location.
• Solar PV for qualifying newly constructed detached ADUs (or solar-ready conduit), and battery/energy-storage-ready (ESS-ready) provisions where the applicable energy code requires them.

Why the load calculation comes first

Almost every other decision — panel amperage, whether your main service needs an upgrade, whether a subpanel feed will work — flows from the Article 220 calculation. Building departments treat it as a required submittal, and missing or unsupported sizing is one of the most common plan-check corrections we see. It must be performed by a licensed electrician or MEP engineer, not estimated.

A quick pre-design checklist

1. Confirm your main service size (100A, 125A, 200A) and how loaded it already is.
2. Decide all-electric vs. mixed-fuel early — it drives panel sizing significantly.
3. Identify the EV charging location and the path for conduit.
4. Check whether your city's reach code adds EV-capable, ESS-ready, or solar requirements.
5. Contact your serving utility about metering before plans are finalized.

Requirements vary by jurisdiction and utility — confirm specifics with your local building department and serving utility. Our ADU electrical plans bundle the load calc, panel schedule, and code notations into one permit-ready set; see pricing for single-discipline and full MEP options.