Title 24 Water Heater Requirements
It depends on whether the home is new. A new home on the prescriptive path needs a 240-volt heat pump water heater or solar water heating with electric backup. A replacement in an existing home can still be gas or propane, or a heat pump water heater installed to set conditions, and new and accessible hot water pipes must be insulated.
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New homes: the prescriptive options
Section 150.1(c)8 gives a new single-family home three prescriptive choices:
- a single 240-volt heat pump water heater with the tank in the garage or conditioned space; zones 1 and 16 add a compact hot water distribution design, and zone 16 also needs a field-verified drain water heat recovery system
- a single 240-volt heat pump water heater meeting the NEEA Advanced Water Heater Specification Tier 3 or higher; in zone 16 the tank goes in the garage or conditioned space and drain water heat recovery is added
- solar water heating with electric backup and a solar savings fraction of at least 0.7
Two exceptions help small units. A dwelling of 500 square feet or less may use an electric water heater with point-of-use distribution, and a unit with one bedroom or less may use a 120-volt heat pump water heater. If there is a recirculation loop, only a demand system with manual on/off control is allowed. Your zone is on the climate zone page.
Gas and tankless in a new home
None of the prescriptive options is gas. A gas storage or gas tankless water heater in a new home complies through the performance path, with the difference balanced elsewhere in the energy model.
It also brings the electric-ready provisions of §150.0(n). The home sets aside a space at least 2.5 feet by 2.5 feet and 7 feet tall for a future heat pump water heater, and wires it:
- if the space is within 3 feet of the water heater: a dedicated 125-volt, 20-amp receptacle on a 120/240-volt three-conductor branch circuit rated at 30 amps or more, the spare conductor labelled and isolated, and a reserved breaker space marked "Future 240V Use"
- if the space is further away: a 240-volt, 30-amp circuit within 3 feet of it, reserved panel space for a double-pole breaker, and the cold and hot water piping routed through the space
- in both cases, a condensate drain no more than 2 inches above the base of the water heater that drains without a pump
The compliance manual is explicit that these provisions apply to new homes and to additions where a water heater is installed. They do not apply to alterations, or to an electric water heater.
A gas tankless heater has one more mandatory detail wherever it goes. Instantaneous units above 6.8 kBtu/h need isolation valves on both the cold supply and the hot outlet, with hose bibbs or other fittings for flushing.
JA13 and heat pump water heater controls
Joint Appendix JA13 sets the qualification requirements for a heat pump water heater demand management system: the controls that let the water heater shift when it heats, day to day, to cut bills and use more of a home’s own solar. It is not a prescriptive requirement. It earns a compliance credit on the performance path, and the compliance manual notes that the credit varies by climate zone.
To qualify, the system must be certified to the Energy Commission, the water heater must meet NEEA Tier 3 or higher, and a thermostatic mixing valve conforming to ASSE 1017 must be fitted, unless the water heater itself conforms to UL 60730-1, ASSE 1082 or ASSE 1084. Certified products are listed on the Energy Commission’s JA13 page.
Replacing a water heater
A replacement is an alteration under §150.2(b)1H. The new water heater must be one of these:
- a natural gas or propane water heater, which includes gas tankless
- a single heat pump water heater, with the tank not outdoors, standing on a rigid insulated surface of at least R-10, and fitted with a communication interface meeting §110.12(a) or an ANSI/CTA-2045-B port
- a heat pump water heater meeting NEEA Tier 3 or higher
- a consumer electric water heater, if the existing one is electric resistance
So the 2025 code does not force a switch from gas at replacement. It does set the terms if you choose a heat pump, and the electric-ready provisions above do not apply.
The same section requires pipe insulation on newly installed piping and on existing piping that is accessible, to the levels in §150.0(j)1, which points to Section 609.12 of the California Plumbing Code. Inaccessible pipe is not covered.
Adding a second water heater as part of an addition is treated differently. The prescriptive options there are a heat pump water heater, or an electric point-of-use heater for additions of 500 square feet or less. A gas tankless heater in an addition needs the performance path. More on additions is on does a room addition need Title 24.
Pipe insulation in new homes
All domestic hot water piping in a new home is insulated to the plumbing code. The exceptions are narrow: pipe passing through framing, pipe already surrounded by at least 1 inch of wall, 2 inches of crawlspace or 4 inches of attic insulation, and pipe inside walls where Quality Insulation Installation is met.
The permit
The permit for a water heater replacement comes from your local building department, and the department decides what Energy Code documentation it wants with it. The equipment has to meet §150.2(b)1H either way. Central water heating in apartment buildings follows different rules, covered on multifamily water heating requirements.
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
Yes. Under §150.2(b)1H a natural gas or propane water heater is an allowed replacement in an existing home. New and accessible hot water pipes still need insulation.
Yes as a replacement in an existing home. In a new home a gas tankless heater is only possible through the performance path, with the electric-ready space and wiring of §150.0(n). Units above 6.8 kBtu/h need isolation valves for flushing.
The Joint Appendix that qualifies heat pump water heater demand management systems for a performance compliance credit. It requires a NEEA Tier 3 or higher water heater, scald protection and certification to the Energy Commission.
The new-home prescriptive options call for a 240-volt unit, with a 120-volt unit allowed in a dwelling of one bedroom or less. The replacement options in §150.2(b)1H do not specify a voltage.
Your building department issues the permit and sets what it needs with it. The replacement has to meet the Energy Code whatever the paperwork.