ADU electrical wiring & power in San Luis Obispo County
Load calculations, subpanels, separate services, and full ADU wiring from rough-in through finish. I tell you whether your existing service can carry the unit before the plans are final.
California C-10 licensed · Insured · Serving SLO, Atascadero & Paso Robles
What an ADU needs electrically
I'm Adam Keif, a C-10 licensed residential electrician based in San Luis Obispo. An ADU is not a scaled-down house. It is a complete dwelling in a small footprint, and it has to get its power from a property that was wired for one home. That is where most of the real decisions are.
- A load calculation on the existing service. The first question is whether what you already have can carry a second dwelling. I run the numbers rather than guessing, and I would rather tell you in the design phase than after the drawings are done.
- Subpanel or a separate service. The unit either runs off a subpanel fed from the existing service or gets its own. That single decision moves the cost, the permit, and the utility timeline more than anything else on the electrical scope.
- The feeder and the trench. For a detached unit, power has to physically get there. Feeder sized for the load and the distance, conduit or direct burial, trench depth to code, and a disconnect where it belongs.
- A panel upgrade, when the numbers say so. Adding a dwelling is frequently what pushes an older service past what it can carry. Panel upgrades.
- Full interior wiring, rough-in to trim. Kitchen circuits, bathroom GFCI protection, heating and cooling, laundry, smoke and carbon monoxide detection, lighting, and exterior fixtures. A whole house worth of circuits in a few hundred square feet.
- Title 24 and electric-ready requirements. New ADUs carry energy-code requirements that can affect the electrical design, including electric-ready and battery-storage-ready provisions. I account for those when planning the service, the panel, and the wiring, so the system is not designed around yesterday’s load.
- Permits and inspection. Pulled and scheduled as part of the job, through the City or the County depending on where the property sits.
Subpanel or a separate meter?
This is one of the first electrical decisions worth settling, because it can affect the budget, the drawings, the permit, and the utility timeline.
Attached or detached, the question is the same: what does the unit require, and can the existing service support it? A detached unit adds a feeder and a trench to get power across the property. An attached unit or a conversion of existing space skips that, but can bring its own constraints depending on how the space was wired and where the service enters.
Running off the existing service
If the existing service has capacity, the cleanest answer is usually a subpanel in the ADU, fed from the main house. One utility account, no new meter, and the work stays on your property and your schedule. The constraint is capacity: a load calculation has to show the existing service can carry the house and the new dwelling together. On a property still running an older, smaller service, it often cannot, and then a panel upgrade comes first.
Giving the ADU its own service
A separate service means its own meter and its own utility account, which some owners want for a rental. It also means involving PG&E, and that is the part that adds time. Utility engineering review and crew scheduling run on their own calendar, not yours, so if a new service is the answer it should be identified early rather than discovered late.
What decides it
Partly the numbers, partly the rules. California law limits when a local agency can require a separate utility connection or meter for an ADU, but the utility has its own requirements, and those often depend on whether the unit is detached, attached, or a conversion of existing space. Rather than assume, I confirm the requirement with PG&E and the building department for your specific project, then size and price the work around the real answer.
California opened ADUs up. The service still has to carry it.
California and San Luis Obispo County have made ADUs easier to build in several ways, and the County updated its ADU regulations in 2025. None of that tells you whether a given property’s electrical service can support the unit.
Two properties on the same street, both approved for an ADU, can have completely different electrical scopes and costs depending on the age and size of the existing service. That gap is where I am useful, and it is worth closing before the design is locked.
Your designer, builder, or planner is the right person for zoning and ADU requirements, and you should confirm the current rules with the jurisdiction that will issue the permit. My job is to work out what the electrical system needs to make the approved design work.
For contractors and owner-builders
I also work as a sub for ADU contractors and owner-builders. If you build ADUs, here is how I work and what makes the electrical go smoothly.
Bring me in during design, not at rough-in. The load calculation and the service decision belong on the drawings. When they get answered late, the fix is either a panel upgrade nobody budgeted for or a utility application that holds up the schedule.
What I need from you. The plan set, the appliance and mechanical schedule, and whether the unit is intended to be separately metered. From that I can give you a real number instead of an allowance.
What you get. One person who quotes the job and then does it. Rough-in coordinated to your framing schedule, trim when you are ready for it, permits pulled and inspections scheduled, and a panel left labeled so the final walkthrough is not an argument. If the schedule slips, you tell me directly. See new construction & remodels for how I handle full builds.
How I work
You call or send a quote request with whatever you have, even if it is just an idea and an address. For an ADU I will come out and look at the existing service at no cost, because that visit is what makes the rest of the numbers real.
You get a written quote before any work begins. Flat-rate where possible, no add-ons you did not agree to.
Permit requirements depend on the work and the jurisdiction. ADU wiring, new services, and panel upgrades commonly require permits, and those go through the city where the property sits or through San Luis Obispo County Planning & Building for unincorporated areas. When the work requires a permit, I pull it and handle the inspection.
Why ADU owners and builders hire Keif Electric
- Owner-operated. You get me on your job, not a rotating crew.
- Licensed and insured. California C-10, CA# 1152084.
- Reliable on schedule. Rough-in stays on pace; I don't hold up the build.
- Clean, code-compliant finish. Labeled panels, tidy work, passes inspection.
Can my existing panel and service handle an ADU?
That is the first question to answer, and it is worth answering before the plans are final. An ADU is a complete dwelling: kitchen circuits, bathroom GFCI protection, heating and cooling, laundry, and its own load. I run a load calculation on the existing service and tell you whether it carries the unit as-is, needs an upgrade first, or the ADU needs its own service.
Does an ADU need its own electrical meter?
Not always, and it is worth checking early because it affects cost and schedule. California law limits when a local agency can require a separate utility connection or meter for a qualifying ADU, and the utility applies its own requirements, which often turn on whether the unit is detached, attached, or a conversion of existing space. I confirm the requirement with PG&E and the local building department for your specific project rather than assuming.
When should an electrician be involved in an ADU project?
Earlier than most people expect. A load calculation and the subpanel-or-separate-service decision belong in the design phase, because both can change the drawings, the budget, and the utility timeline. Bringing me in at rough-in means those questions get answered when it is expensive to change the answer.
Can you wire a prefab or modular ADU?
Yes, and pre-reviewed plan sets too. San Luis Obispo County offers pre-reviewed ADU designs, and prefab and modular units are common here. The unit itself may arrive largely wired, but the site work is still a project: the feeder from the house or a new service, trenching, the disconnect, grounding, and tying it into a panel that can actually carry it.
Do you work with ADU contractors and owner-builders?
Yes, regularly. I sub for contractors and owner-builders on ADUs across SLO County, from full rough-in through finish trim, coordinated to your schedule. If you build ADUs and want an electrician who quotes the job and then shows up to do it, call me.
Call(805) 286-0477
Tell me the address and what you are planning. I will look at the existing service and tell you what the ADU actually needs, before the drawings are locked.
Or text me at the same number.- California C-10 #1152084
- Liability insured
- Mon–Fri, 9am–5pm
Adam Keif, owner. Reads every request and calls back the same business day.