California's 2025 energy code: new rules for AC and window swaps

If you are replacing an air conditioner, a heat pump or a few windows in California, the rules your contractor follows changed this year. The 2025 California Energy Code, part of Title 24, applies to building permit applications submitted on or after Jan. 1, 2026. Knowing the basics helps you read quotes and spot a contractor who plans to skip steps.

Replacing a heat pump or AC. Under the alteration rules, all air-source heat pumps, and air-cooled air conditioners in climate zones 2 and 8 through 15, must have their airflow and refrigerant charge checked by an independent rater. Your building department or contractor can tell you which climate zone you are in. The 2025 code also removed an option that let some systems skip this check by installing a fault indicator display.

Why it matters for you. A heat pump with the wrong refrigerant charge or poor airflow can use more power and heat or cool less evenly. The verification is a third-party check that the system was installed to spec. If a quote has no permit or no verification line, ask why.

A name change to know. The old HERS program, which handled these field tests, has moved into Title 24 as the Energy Code Compliance (ECC) program. You may now see "ECC-Rater" on paperwork where you used to see "HERS rater."

Replacing windows. Replacement windows up to 75 square feet must have a U-factor of 0.40 or lower in every climate zone (U-factor measures heat loss; lower is better). In climate zones 2, 4 and 6 through 15, they also need a solar heat gain coefficient of 0.35 or lower, which limits how much summer sun heat comes through. Skylights are capped at a U-factor of 0.40 and 0.30 for solar heat gain. Ask for both numbers in writing so you can check a quote yourself.

Adding on. Additions over 700 square feet must meet the same window requirements as new homes, and new HVAC equipment for an addition is subject to load calculation and sizing limits. Gas tankless prescriptive options were removed for additions; all-electric water heaters with point-of-use distribution are allowed in additions up to 500 square feet.

New homes. For new construction, heat pumps are now the baseline for space heating and water heating. Gas is still possible through the performance path, which models the whole house, but trade reporting notes the other requirements make it more expensive in most climate zones. New homes with electrical service over 125 amps must also be ready for a future battery, unless one is installed.

Permit review can take time as cities and counties adjust. Trade reporting described two- to four-week review delays in March as jurisdictions adapted to the new standards, so build that into your schedule.

Today's step: if you have an HVAC quote, check that it includes a permit and the required field verification. If it does not, ask the contractor to add both in writing.