Policy · Analysis

Every new home in the basin comes with solar now. What the code actually requires.

Since 2020, Title 24 has required most new California homes to be built with a solar system sized to the house. We walk the requirement, the size formula, the exemptions, and the millions of roofs it never touches.

BY THE RENEWABLE ENERGY LA EDITORS · FILED OCTOBER 31, 2026 · 6 MIN READ ·

What the code actually requires

The mandate's core took effect on January 1, 2020, under the 2019 version of the standards. Most new low-rise homes, meaning three stories or fewer, have to be built with a rooftop solar system sized to the house. There is no opt-in. The builder either installs it, qualifies for a narrow exemption, or meets an approved alternative.

A 2022 update, in force for permits since the start of 2023, pushed further. It moved many new commercial buildings and high-rise apartments toward solar paired with battery storage, and it nudged new homes toward electric-ready wiring and heat pumps. The exact mix depends on building type and climate zone, so two projects a few miles apart can face different numbers.

The size formula, and the ways out

The required system size is not a flat number. The code runs a formula tied mainly to the home's conditioned floor area and its climate zone, so a larger house in a hotter inland zone owes more kilowatts than a compact coastal one. At last public guidance from the Energy Commission, a typical new single-family home landed somewhere in the low single-digit kilowatts, often on the order of two to four, but your figure depends on the plans. Builders can shave the requirement by making the house more efficient first.

Those exits are real but narrow. A roof too shaded, too small, or wrong-facing can earn a reduction, and there are compliance paths that substitute a shared or community solar system, or add battery storage, instead of panels on that specific roof. None of this is a blanket waiver. If you want to check a specific home, the permit file at the local building department will show which path the builder took.

The millions of roofs it never touches

This mandate is for new construction and, in some cases, major remodels. It does nothing to the millions of existing homes across the basin, the older stucco tracts in the San Fernando Valley, the bungalows in the flats, the apartment stock built long before anyone sized a kilowatt to a floor plan. If you already own, the code does not require you to add solar, ever.

What you can earn for exporting power, though, depends on who sells you electricity, and in LA that splits two ways. Homes served by the Los Angeles Department of Water and Power, the city's own municipal utility, fall under its net metering terms, which the city sets on its own. Homes served by Southern California Edison across much of the rest of the basin fall under the state's net billing tariff, the successor to older net metering, which credits exported solar at a lower rate than it once did. Same panels, different payback, depending on your meter.

Worth watching this month

1. The Energy Commission's 2025 standards, applying to permits pulled from January 1, 2026, are worth a look for any tightening of the storage rules, though much of the core solar requirement is already settled.

2. LADWP's net metering terms, posted on the utility's solar pages, can change on the city's own schedule, so anyone weighing a new install should confirm the current credit before signing.

3. The state's net billing tariff at the CPUC, which governs Edison customers rather than LADWP ones, remains the subject of ongoing proceedings worth checking if you are on SCE.

4. New-home permit activity at the Los Angeles Department of Building and Safety is a routine but telling signal of how much of this stock is actually getting built this year.

Where this dispatch reads

California Energy Commission, Building Energy Efficiency Standards (Title 24), www.energy.ca.gov/programs-and-topics/programs/building-energy-efficiency-standards, The state agency that writes the code, and the official source for what each standards cycle requires.
California Energy Commission, 2022 Energy Code solar and storage summary, www.energy.ca.gov/programs-and-topics/programs/building-energy-efficiency-standards/2022-building-energy-efficiency-standards, Plain summaries of the solar and battery provisions added in the 2022 update.
Los Angeles Department of Building and Safety, www.ladbs.org, The city permit office that enforces Title 24 and holds the permit file for any new LA home.
Los Angeles Department of Water and Power, solar and net metering, www.ladwp.com, The municipal utility's own rooftop solar and net metering terms, which it sets independently of the state.
California Public Utilities Commission, net billing tariff, www.cpuc.ca.gov/nembillingtariff, The export-credit rules for Edison and other investor-owned utility customers, not LADWP.

Questions readers have asked

Does my existing house now need solar?

No. Title 24's solar requirement applies to new construction and certain major alterations, not to homes already standing. You can add solar voluntarily, but the code does not force it.

Who enforces this in Los Angeles?

Your local building department does, at permit time. Inside the city of LA that is the Department of Building and Safety; other basin cities have their own departments applying the same state code.

Can a builder legally skip the panels?

Only within narrow limits. A heavily shaded or very small roof can qualify for a reduction, and approved alternatives like community solar or added battery storage can substitute. A full waiver with no alternative is not the norm.

Does it cover apartments?

Low-rise multifamily has been covered since 2020. The 2022 update extended solar paired with storage toward high-rise multifamily and many commercial buildings, with the details varying by building type and climate zone.