Does a New ADU in Los Angeles Need Solar?

California's Energy Code (Title 24, Part 6) has required solar PV on most new low-rise homes since 2020. The current 2025 edition took effect January 1, 2026, and it carries that idea forward to accessory dwelling units. In plain terms:

A newly constructed, detached ADU — a brand-new backyard cottage built from the ground up — must include its own solar PV system, sized to the unit, unless a specific exemption applies (California Energy Commission, Section 150.1(c)14). An attached ADU is treated by the code as an addition to your existing home, and an ADU created by converting existing space — a garage conversion, or carving a unit out of the main house — is treated as an alteration. Additions and alterations do not trigger the new-construction solar requirement.

This is code interpretation, not tax advice, and your local building department — in the city of Los Angeles that's LADBS — plus a Title 24 energy analyst have the final say on your specific project. Use the table below as a starting map, then confirm.

The code sizes the required system with an equation driven by the unit's conditioned floor area and the number of dwelling units, using coefficients that change with your climate zone (Los Angeles County spans several — coastal, basin, valley, and high desert all differ). Roughly: a bigger, more air-conditioned unit in a sunnier zone needs a bigger array. Because ADUs are small, the required system is often modest — frequently just a few kilowatts.

That's also why the minimum-size exemption matters: if the code-calculated array comes out to less than about 1.8 kW, the unit is exempt and no PV is required — but this threshold follows the current applicable Energy Code and can change, and project-type exceptions apply, so verify against the current code for your project. Very small or heavily shaded ADUs can land there. For a plain-English walkthrough of sizing an array to your actual electricity use — a different question from the code minimum — see how many solar panels you need.

For a new detached ADU, the code cares that a system sized to that unit exists — not always which roof the panels sit on. Where they physically go, and how they connect, comes down to two things: which electric meter serves the ADU and where the sun actually is on your lot.

If the ADU shares the main house's meter and account (one account for the property), the required solar can often be mounted on whichever roof has the best exposure — the main house, a garage, or the ADU — and still serve the property. A separate ADU meter does not by itself require the new PV modules to connect to that meter — the added capacity may sometimes be incorporated into the main-house system, subject to the approved Title 24 model, the permit set and your utility's interconnection rules. Final say on placement and interconnection depends on your utility and LADBS; the applicable NEC edition, your service configuration, and equipment vary, so confirm the design before you commit.

Which utility serves your address changes how much that solar is worth — and therefore how you'd design an ADU system.

LADWP (the municipal utility for most of the city of Los Angeles) still offers its own municipal solar rate schedules (separate from NEM 3.0 and generally more favorable than the IOU Net Billing Tariff — confirm the applicable current schedule), and it is not on NEM 3.0. That makes sizing for a full offset — and netting the whole property together on one meter — an easy call. Details in our LADWP net metering guide.

SCE and the other investor-owned utilities are on NEM 3.0 (the Net Billing Tariff), where exports earn a time-varying credit that's usually far below retail — an illustrative 5–8¢/kWh at common midday hours, with a few late-summer evening hours worth much more. There, the smart move is designing for self-consumption plus a battery rather than sending power to the grid, and the meter split matters more because exported ADU power is worth little. We break this down in NEM 3.0 explained.

An ADU solar project in the city of Los Angeles is permitted through LADBS, usually alongside the ADU's own building permit. Expect a solar PV permit (often eligible for expedited or online review for standard rooftop systems) and, where the work calls for it, electrical permits for a new subpanel, a service change, or a separate meter. A new separate service also means setting up a new account with your utility.

Whether you need a main-panel or service upgrade depends on the added load and your existing service — it's a load calculation your electrician runs, and the answer varies with the applicable NEC edition, your AHJ, and equipment configuration. Our full walkthrough of the local process is in solar permits in Los Angeles (LADBS).

Bottom line: if you're building a new detached ADU in Los Angeles, plan for solar from day one — size it with your Title 24 analyst, decide the meter setup early because it drives your net-metering math, and confirm any exemption rather than assuming it. If you're converting a garage or building an attached unit, you're likely free of the mandate, though solar can still pay off on its own. This is general guidance, not code or tax advice; your AHJ (LADBS), your utility, and a Title 24 professional confirm the specifics for your address. Want a straight answer for your lot? Call +1-323-844-7777.