Should I use a heat pump?

In nearly every California ADU, yes — a heat pump is the right choice and increasingly the required one. It delivers heating and cooling from a single all-electric unit, runs far more efficiently than electric-resistance heat, satisfies the state's heating mandate, and is the prescriptive baseline under the 2025 energy code.

How a heat pump works (and why "it won't heat in cold" is outdated)

A heat pump doesn't generate heat by burning fuel or running resistance coils — it moves heat with a refrigerant cycle. In summer it pulls heat out of the indoor air; in winter the cycle reverses and it extracts heat from outdoor air, even when it's cold, and delivers it inside. Because moving heat takes far less energy than creating it, a modern unit delivers roughly two to four units of heat per unit of electricity. Older heat pumps lost capacity as temperatures dropped, but modern cold-climate-rated models use variable-speed inverter and vapor-injection compressors to hold rated capacity well below freezing.

Heat pump vs. the alternatives

Reasons to choose a heat pump

• Two functions, one unit — it satisfies the code requirement to maintain 68°F in every habitable room and provides cooling, which is effectively essential in the hot inland and desert zones.
• All-electric compliance — required where reach codes prohibit gas, and favorable for Title 24 everywhere.
• Low operating cost in California's mild climate.
• Incentive eligibility — many state, utility, and federal programs target heat pump installations (programs and amounts change frequently; verify current eligibility for your address).

Selection checklist

1. Confirm your climate zone by parcel address.
2. Run a Manual J to size the unit to the actual load.
3. In Zone 16 (and cold edges of 1 and 11), specify a cold-climate-rated model and check capacity at the design temperature, not just at 47°F.
4. Verify the unit meets current Title 24 SEER2/HSPF2 minimums.
5. Note refrigerant-charge HERS verification, required in all 16 zones.

A common worry, addressed

Owners sometimes ask whether one heat pump can carry both the coldest winter morning and the hottest summer afternoon. The answer is yes, when it's sized from a real Manual J rather than a rule of thumb. The load calculation pins the equipment to your ADU's actual peak heating and cooling demand at your zone's design temperatures, so a single correctly specified unit holds setpoint year-round without the short-cycling that comes from oversizing. In multi-room ADUs, a multi-zone configuration adds independent control room by room while still running off one outdoor condenser.

Equipment ratings and local mandates vary by jurisdiction and code cycle — confirm with your local building department. Our mechanical plans specify the exact heat pump, sized and scheduled for your ADU, and bundle cleanly with a Title 24 report. Start your order when ready.