Title 24 Heat Pump Requirements for Homes
For a new single-family home, the 2025 prescriptive package requires the space-conditioning system to be a heat pump in all 16 climate zones (§150.1(c)6). A gas furnace is only possible through the performance path. In an existing home the state code does not require a heat pump, but installing one brings refrigerant charge verification in every zone.
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New homes: the heat pump is the baseline
Section 150.1(c)6 is short. The space-conditioning system shall be a heat pump, or the building shall comply through the performance approach. Table 150.1-A confirms it zone by zone: in all 16 climate zones electric resistance space heating is not allowed, gas space heating is marked NA, meaning not allowed, and a heat pump at the minimum required efficiency is the expected system.
There is one small allowance. A supplemental heater may serve a space already served by the primary system, provided it is no larger than 2 kW (7,000 Btu/h) and is controlled by a timer of 30 minutes or less. It is a top-up, not a heating system.
The performance path is the alternative
A new home can still have a gas furnace. It complies through the performance approach in §150.1(b), where approved software models the proposed home against a standard design built to the prescriptive package, heat pump included. Whatever the proposed system does differently has to be balanced within that energy budget.
A furnace also brings a mandatory requirement. Under §150.0(t), a gas or propane furnace serving a dwelling unit needs a dedicated 240-volt branch circuit, rated at 30 amps minimum, within 3 feet of the furnace and labelled "240V ready", plus a reserved double-pole breaker space in the main panel marked "For Future 240V use". The house is wired for the heat pump it did not get.
Heat pumps can earn credit on the performance path too. Where compliance depends on one, its rated heating capacity at 47°F and 17°F is field verified, and a system claimed under the variable capacity heat pump option is verified as well.
Rules every heat pump has to meet
These are mandatory under §150.0(h) and §150.0(i), whichever path the home takes:
- Sizing. Equipment is selected under ACCA Manual S-2023 from a load calculation, and the heating capacity must meet the building code minimum without counting any supplementary heat.
- Backup heat locked out. Electric resistance or gas furnace backup must be locked out above an outdoor temperature of no more than 35°F, except during defrost or when the occupant selects emergency heat. Homes under 500 square feet, and homes in zones 7 and 15, may use an alternative control instead.
- Backup heat sized. Electric resistance backup may not exceed 2.7 kW per ton of the heat pump’s nominal cooling capacity.
- Thermostat. With supplementary heat, the thermostat must receive and display the outdoor temperature and show when backup or emergency heat is running.
- Defrost. An installer-adjustable defrost delay timer is set to 90 minutes or more, except in zones 6 and 7 and for homes of 500 square feet or less in some other zones.
The installer certifies the control settings on the Certificate of Installation (CF2R).
Field verification
Under the 2025 code, heat pump refrigerant charge verification is required in all 16 climate zones. For air conditioners it is limited to zones 2 and 8 to 15. A ducted system on a new home also needs its airflow confirmed at 350 cfm per ton or more, and its ducts leakage tested. An ECC-Rater carries out the checks. A packaged unit charged and verified at the factory is the exception for charge: the installer certifies the factory charge instead, and a ducted packaged unit still has its airflow checked. The detail is on refrigerant charge verification and duct leakage testing.
Replacing a system with a heat pump in an existing home
The statewide code does not make you switch. Section 150.2(b) has no rule requiring a heat pump when an air conditioner or furnace is replaced. The Energy Commission’s 2025 summary lists a heat pump in place of an air conditioner in an existing single-family home among the voluntary CALGreen elements that a city or county may adopt as a local reach code, so check locally.
If you do install one, the alteration rules apply. The new equipment meets the mandatory controls above. Replacing the air handler, outdoor unit or coil triggers duct sealing verified by an ECC-Rater, unless an exception applies. And because it is a heat pump, §150.2(b)1F requires refrigerant charge verification in every zone, and an airflow of at least 300 cfm per ton for a ducted system, where an air conditioner would need them only in zones 2 and 8 to 15. The duct thresholds for a replacement are on does an HVAC replacement need Title 24.
One rule points the same way. An altered or replacement space heating system may not use electric resistance as its primary heat source, with narrow exceptions where the existing heat is already electric resistance. Moving off an electric furnace or baseboard heat points towards a heat pump.
Mini-splits
The code names mini-split systems in its refrigerant charge rules, for new homes and for alterations alike. A mini-split heat pump needs its charge verified in every zone. Where the standard procedure cannot be used, the installer weighs in the charge and an ECC-Rater verifies it.
What a ductless system avoids is the duct work: there is no duct leakage test and no ducted airflow requirement. In a new home, a ductless system is also one of the exceptions to the mandatory roof-deck insulation requirement in zones 4 and 8 to 16.
The wider changes in this cycle are summarised on what changed in the 2025 Energy Code.
Common Title 24 Questions
- When is Title 24 required for a home?
- Does a remodel need Title 24?
- Does a room addition need Title 24?
- What plans are needed for a residential Title 24 report?
- How much does a residential Title 24 report cost?
- How long does a residential Title 24 report take?
Frequently Asked Questions
No. A gas furnace cannot be used on the prescriptive path, but a home can still comply with one through the performance path. The furnace location then needs a 240-volt circuit and panel space for a future heat pump under §150.0(t).
Not under the statewide Energy Code. The Energy Commission lists it as a voluntary CALGreen measure for local reach codes, so your city or county may have its own rule.
A heat pump mini-split needs its refrigerant charge verified by an ECC-Rater in every climate zone. A ductless system has no duct leakage test.
Yes, as supplementary heat. Electric resistance backup is limited to 2.7 kW per ton of cooling capacity and must be locked out above 35°F, except during defrost or emergency operation.