Title 24 Solar Requirements: How They Affect Your Electric Bill

When you buy or build a new home in California, solar panels come with it, whether or not you asked for them. That is not an add-on you can opt out of. It is the law. Since 2020, California's building code has required solar on new construction homes, including ADUs. Here is what the Title 24 solar requirements typically cover, and why "the house design includes solar" does not mean what most people assume it means.

What is Title 24?

Title 24 is the section of California's building code, overseen by the California Energy Commission, that sets Building Energy Efficiency Standards for new construction across the state. It sets requirements for many aspects of a new home, including insulation rating, lighting controls, pool and spa pump efficiencies, HVAC equipment specifications, and solar and battery considerations.

Since January 1, 2020, Title 24 Part 6 has required a solar photovoltaic system on all new construction residential buildings. It is anticipated that future Title 24 code updates will add a minimum solar requirement to major remodel projects as well. If the Title 24 calculation results in a solar requirement below 1.8 kW, the requirement is waived.

What the Requirement Covers, and What It Does Not

The size of the mandated solar system is not arbitrary. It is calculated using a formula tied to the home's conditioned floor area and its projected annual electrical usage, adjusted for the climate zone. A house in the high desert and a house near the coast will have different required system sizes even at a similar square footage, because the underlying energy model assumes different heating and cooling loads.

There are exceptions built into the code too. A home with excessive roof shading, or without enough usable roof area to fit a system, can qualify for a reduced requirement or an alternative compliance path. These exceptions are the reason two homes on the same block can have noticeably different solar setups even though both technically comply with Title 24 solar requirements.

The Part Nobody Explains: How Much of Your Bill It Offsets

Here is where the confusion usually starts. Title 24's solar mandate is designed to offset a portion of a home's projected electric load, which typically lands somewhere around 10 to 15 percent of an average home's electric bill.

New-home marketing rarely draws that distinction. A listing that mentions "solar included" leaves plenty of buyers picturing a power bill close to zero. In reality, the code-mandated system leaves a large remaining electric bill. Reading your energy bill line by line makes the gap obvious.

The Title 24 system is the floor, not the goal. It satisfies the code; it does not satisfy your utility bill.

Xero Solar's Approach to Closing the Gap

The Title 24-mandated system is a starting point, not our recommended solution. When advising on new construction builds, the Xero Solar team always provides two proposals: one for the minimum requirement to meet California code, and a second expanded system designed to offset the majority of the home's electric consumption and utility bill. Despite the increase in upfront investment, the recommended system typically has a shorter return on investment because of the additional savings it provides.

• In LADWP territory, the recommended system simply increases the solar array size.
• In SCE territory, battery storage is also included in the recommended system.
• Storage is essential under NEM 3.0 for shifting generation into on-peak hours and increasing the share of generated energy consumed on site.

If you want to go deeper on storage, our guides on battery storage and maximizing storage performance cover sizing and dispatch in detail.

A Clearer Picture of Your Actual Usage

Building a new home? The team at Xero Solar has spent over a decade helping homeowners across the Greater Los Angeles area understand what their Title 24 report requires. We then compare that to a recommended system designed around your home's unique build details and your energy goals. Contact Xero Solar to talk it through.

Frequently asked questions

Does every new home in California require solar under Title 24?

Almost all new residential construction is required to include a solar system under the current energy code, though the exact requirement depends on the building's design, roof area, and climate zone. Your builder, T24 consultant, or the Xero Solar team can confirm what your project's solar requirement is.

Does Title 24 apply to existing homes or renovations?

Title 24 broadly applies to both existing homes and renovations. Today, the solar mandate is only tied to new construction. Existing homes are not required to add solar retroactively, but that may change in future code renditions.

Can I add more panels if my Title 24 system is not covering enough?

Yes, in most cases. A code-compliant system can typically be expanded if the roof space and electrical setup support it. If you are building a new home today, the most cost-effective approach is to incorporate the larger system into your construction project.

Does a Title 24 solar system eliminate my electric bill?

Not on its own. It is designed to offset a portion of typical usage, generally in the 10 to 15 percent range for an average home.

How does Southern California Edison's NEM 3.0 affect what I save?

NEM 3.0 reduced the credit homeowners receive for excess solar sent back to the grid. That makes it valuable to pair solar with battery storage, which increases the percentage of generated energy that is self-consumed on site instead of relying on export credits to discount your bill.