Water Heaters

The water heater is HERS/ECC verified, and the unit installed has to match the one on your CF1R. Exactly. The project cannot deviate from the specified unit — and in some cases that means the exact model number. If a specific heat pump water heater (HPWH) is called out, that unit was modeled for your project — substituting a different unit, or installing a gas tankless instead, triggers a revision that adds time and cost. In some cases the wrong unit has to be removed and replaced.

Heat pump water heater, verified against the CF1R.

No deviations

The project cannot deviate from the water heater specified on the CF1R. When the CF1R lists a specific model number, that exact model is what has to be installed.
If the plans call for something different than the CF1R, it must be addressed before installation — not at final.
Any ADU that uses the solar (PV) exception cannot achieve compliance with a gas water heater. The exception requires all-electric — a gas tank or gas tankless will fail.

What has to match

From the water heating table on your CF1R.

Type

HPWH, tankless, storage

The type of water heater on the CF1R. A gas tankless in place of a modeled HPWH (or the other way around) needs a CF1R revision.

Efficiency

UEF · input BTU

The UEF must meet or exceed the CF1R. For gas tankless, the input rating must match too.

NEEA listing

When the CF1R says NEEA

A NEEA HPWH is a specific unit from a specific list, not just any heat pump water heater. Check the NEEA Qualified Products List before ordering.

HPWHs need the right location. They exhaust cold air and need enough space and ambient temperature to perform. In a small, enclosed utility space — common in ADUs — that can create moisture and comfort problems. Prescriptively, the tank goes in the garage or conditioned space. §150.1(c)8

*NEW FOR 2025* Mandatory HPWH installation rules. Ventilation: the space the HPWH is installed in must have at least 100 cubic feet per kBtu/h of compressor capacity (or the manufacturer’s minimum, if greater) — or be vented to an adjoining space through louvered doors or upper and lower openings sized per the code, or ducted per the manufacturer. Backup heat: required when the HPWH draws unconditioned inlet air, unless its compressor cut-off temperature is below the Heating Winter Median of Extremes for the nearest location in Joint Appendix JA2. §110.3(c)7

What to expect

How we handle water heaters when you hire us.

Before you buy

Send us the model first

Plumbers play a bigger role in Title 24 compliance than most realize. Send us the make and model before it’s ordered — we check it against the CF1R (and the NEEA list when required). At inspection we verify the installed model, UEF and location against the CF1R, and that hot water pipe insulation is in place where required.

§150.1(c)8 · §150.0(n)

Common failures & how to avoid them

From our GC workflow.

Common failures

UEF rating below the CF1R specification
Gas tankless: input BTU or UEF doesn’t match the CF1R
HPWH: model not on the NEEA Qualified Products List when the CF1R calls for NEEA
HPWH: installed where the ambient temperature falls below the manufacturer minimum
Missing pipe insulation where the CF1R requires it

Prevention

Match the water heater type, UEF and input rating exactly to the CF1R — don’t substitute
HPWH: check the model on the NEEA Qualified Products List before ordering
Insulate hot water piping before drywall when the CF1R requires it
Have the spec sheet on site at the inspection

The code

Click a section to read the actual code language, or open it in the official CEC document.

§150.1(c)8Prescriptive water heating

Water-heating systems shall meet the requirements of A, B, C, or shall meet the performance compliance requirements of Section 150.1(b)1…
A. A single 240 volt heat pump water heater (HPWH). The storage tank shall be located in the garage or conditioned space…
B. A single 240 volt HPWH that meets the requirements of NEEA Advanced Water Heater Specification Tier 3 or higher…
C. A solar water-heating system with electric backup… with a minimum annual solar savings fraction of 0.7.
Exception 1: For climate zones 3, 4, 13 and 14, a gas or propane instantaneous water heater with an input of 200,000 Btu per hour or less and no storage tank may be installed. NOTE: The space conditioning system shall be a heat pump as specified in Section 150.1(c)6.

Choosing a water heater?

Send us the make and model before you order.