ADU Guide

ADU Electrical Requirements in California:
What Every Homeowner Needs to Know

By Mario Orejel  ·  New Ground Electric

Why ADUs Are Booming in Southern California

California's ADU laws have made it easier than ever to add a secondary dwelling unit to your property. Whether you are building for rental income, a family member, or long-term property value, the electrical work is one of the most critical — and most misunderstood — parts of the project.

In Riverside County and San Diego County, ADU projects are increasing dramatically. Homeowners are converting garages, building detached units, and adding junior ADUs inside existing homes. Every one of them requires careful electrical planning from the start.

What Electrical Work Does an ADU Require?

The scope of electrical work depends on the type of ADU, but most projects include:

• A dedicated subpanel inside the ADU fed from the main residence panel
• An underground feeder in conduit from the main panel to the ADU subpanel
• Complete interior wiring — outlets, switches, lighting, kitchen circuits, bathroom circuits
• AFCI protection on most branch circuits per 2022 California Electrical Code
• GFCI protection in kitchens, bathrooms, and all exterior locations
• Smoke and carbon monoxide detectors
• Electrical permit pulled and inspections passed at each phase

Do You Need a Separate Panel for an ADU?

Yes. California code requires a dedicated means of disconnect for an ADU — meaning the ADU needs its own subpanel or main disconnect separate from the main residence. This protects both the homeowner and any tenant by providing independent circuit control and overcurrent protection.

The subpanel is fed via an underground feeder from your main panel. The feeder must be properly sized based on a load calculation — not guessed. Undersized feeders are one of the most common and costly mistakes in ADU electrical work.

Can Your Existing Panel Handle an ADU?

This is the first question we answer on every ADU quote visit. A 200A main panel in good condition can typically support an ADU feeder with capacity to spare. A 100A panel — common in homes built before 1990 — often needs upgrading before an ADU can be properly served.

We assess your panel, calculate your existing loads, and give you an honest answer before any work begins. If an upgrade is needed, we include it in the scope and price it transparently.

What About a Second Meter for Your ADU?

If you plan to rent your ADU, a separate utility meter gives your tenant their own SCE / SDG&E account. This is cleaner for billing, avoids disputes over shared utility costs, and is increasingly standard for income-producing ADUs.

We prepare the service entrance for a second meter socket, submit the paperwork to SCE / SDG&E, and coordinate the utility inspection. The utility company installs the physical meter. Timeline is typically 4 to 8 weeks after application.

Permits — Do You Really Need Them?

Yes — always. Unpermitted ADU electrical work creates serious problems. Your homeowner's insurance may deny claims related to unpermitted electrical. The work will need to be disclosed — and potentially remediated — during a home sale. And if the work is substandard, there is no inspection record protecting you.

We pull every permit and schedule every inspection. ADU electrical permit approval in Temecula and San Diego County typically takes 2 to 4 weeks. We handle the application so you do not have to.

Are There Rebates for ADU Electrical?

Potentially yes. If your ADU includes energy efficiency upgrades — heat pump water heater, mini-split HVAC, induction cooking — there may be SCE / SDG&E rebates and California state incentives available through the Inflation Reduction Act. We can point you toward the right programs during your quote visit, though we recommend checking directly with your utility for current availability.

How Much Does ADU Electrical Cost?

ADU electrical costs in Southern California typically range from $10,000 to $35,000 depending on scope. Key factors include ADU size and circuit count, feeder run distance from the main panel, whether a panel upgrade is needed, second meter coordination with SCE / SDG&E, and city permit fees. We provide written flat-rate quotes after a free on-site assessment — no guessing, no surprises.

What to Look for in an ADU Electrician

Not every electrician has experience with ADU projects. The combination of underground work, load calculations, utility coordination, and multi-phase inspections requires someone who has done it before. Make sure your electrician holds a valid California C-10 license — you can verify any license at the CSLB website. New Ground Electric holds C-10 License #1153189.