Does a water heater replacement need a HERS test?

By Roman Leonelli · CEO & Certified HERS / ECC Rater · CHEERS Rater #RCN13486 · Published June 10, 2026

The short answer

Most like-for-like water heater replacements in California do not trigger a HERS test. Swapping an existing water heater for a similar new unit requires a plumbing permit and must meet Title 24's mandatory equipment requirements, but it doesn't normally put HERS-verified measures on your compliance documents — so no third-party rater visit is required. The picture changes when the water heater is part of a bigger project, or when your compliance documents take water-heating credits that require verification.

What a HERS test is — and who requires it

Title 24 is California's Building Energy Efficiency Standards — Title 24, Part 6 of the California Code of Regulations. When a permitted project includes measures the code says must be independently verified, a certified HERS rater (Home Energy Rating System) performs the field tests. As of January 1, 2026, the California Energy Commission (CEC) renamed this code-compliance program ECC — Energy Code Compliance — so you'll see “HERS rater” and “ECC rater” used interchangeably; the tests are the same (CEC ECC program page).

The paper trail runs on three documents: the CF1R (Certificate of Compliance — the design), the CF2R (Certificate of Installation — the installer's sign-off), and the CF3R (Certificate of Verification — the rater's test results). The CF1R is the answer key: if it lists field-verified measures, a rater is required; if it doesn't, no test. ERE registers all documents with CHEERS, the CEC-approved registry.

When a water heater project does trigger field verification

• It rides along with an HVAC changeout. The water heater itself isn't the trigger — but if the same permit replaces the furnace, air conditioner, or ducts, those measures bring HERS tests like duct leakage testing with them.
• It's part of new construction, an ADU, or an addition. The water heater is then one line in a full CF1R, and the project carries whatever verifications the energy model needs — commonly duct leakage, refrigerant charge, airflow, and QII insulation verification.
• Your performance-path CF1R takes water-heating credits. Credits such as compact hot water distribution or verified pipe insulation require rater verification when they appear on the compliance documents.
• Multifamily central heat-pump systems. Under the 2025 code's prescriptive path, central heat-pump water-heating systems require ECC-rater verification of pipe insulation per Reference Appendix RA3.6.3 — section 170.2(d)2 (CEC multifamily fact sheet).

Not sure which bucket your project lands in? Send us the CF1R — we'll read it and tell you in plain English what's required. Here's how our HERS / ECC testing works.

The 2025 code changed the baseline

For permit applications on or after January 1, 2026, the 2025 Building Energy Efficiency Standards apply; earlier applications stay on the 2022 code (CEC 2025 Energy Code page). On the water-heating side, the CEC's What's New for 2025: Single-Family fact sheet lists two big moves:

• The gas tankless exception is gone. The 2022 code allowed gas tankless prescriptively in climate zones 3, 4, 13, and 14 with heat-pump space conditioning; the 2025 code removes it — section 150.1(c)8.
• Gas tankless is also removed from the prescriptive options for single-family additions — section 150.2(a)1D.

The practical result: the heat pump water heater (HPWH) is now the prescriptive water-heating baseline for new single-family construction and additions. That is not a gas ban — gas equipment can still comply through the performance path, and like-for-like replacements in existing homes follow the alteration rules. For the full picture of what changed, see our guide to the 2025 Title 24 changes.

HPWH readiness: the 30-amp circuit, space, and ventilation rules

A heat pump water heater pulls heat out of the air around it, so the code cares about where it lives and what feeds it:

• Electrical. HPWH-ready construction requires a minimum 30-amp branch circuit at the water heater location — section 150.0(n)1Ai. If you're replacing a gas unit with an HPWH, the circuit is usually the long-lead item; scope it before you commit to a swap date.
• Space and ventilation. HPWH installations trigger ventilation and minimum room-volume requirements under section 110.3(c)7B, so the unit has enough air volume to draw heat from — a sealed closet sized for a gas tank may not qualify without louvered doors or ducting.
• Multifamily HPWH-ready. The 2025 code requires a dedicated receptacle, condensate drain, designated space, and ventilation for individual dwellings and central systems — sections 160.9(e–f).

These are installation requirements certified by the installer — they make the install code-legal, but they are not themselves HERS tests.

What it costs when a test is required

Published market data for Southern California puts a single HERS test visit at roughly $150 to $400, driven by the number of systems and which measures sit on the CF1R (sources: Title 24 Energy Experts cost guide; HomeAdvisor). A full HVAC-changeout package with multiple tests runs higher — our HERS test cost guide breaks down the whole market. ERE quotes a fixed price up front: call (310) 807-4800 with your CF1R or job description and you'll know the number before we roll a truck.

Frequently asked

Does a like-for-like water heater replacement need a HERS test?

Usually not. A standalone swap of an existing water heater for a similar new one doesn't normally carry HERS-verified measures, so no rater visit is required. You still need a plumbing permit, and the new unit must meet the current code's mandatory requirements. The exception is when the water heater is part of a larger permitted project whose compliance documents call for field verification.

Do I need a permit to replace a water heater in California?

Yes. California jurisdictions require a permit for a water heater replacement — typically a plumbing permit covering the installation, seismic strapping, venting, and the temperature and pressure relief discharge. An unpermitted swap can surface later during a home sale or when you pull permits for other work.

Does a heat pump water heater need a HERS test?

Installing a heat pump water heater (HPWH) does not by itself trigger a HERS test in a simple replacement. It does trigger mandatory installation requirements — Title 24 section 110.3(c)7B sets ventilation and minimum room-volume rules so the unit has enough air to draw heat from. On new construction and projects on the performance path, check the CF1R: water-heating measures and credits can carry verification requirements.

What does HPWH-ready mean?

It means the home is wired and plumbed so a heat pump water heater can drop in later without a remodel. Under the 2025 code, new single-family homes need a minimum 30-amp branch circuit at the water heater location per section 150.0(n)1Ai, and multifamily buildings need a dedicated receptacle, condensate drain, designated space, and ventilation per section 160.9.

Can I still replace my gas water heater with another gas unit in 2026?

Yes. The 2025 Energy Code sets heat pumps as the prescriptive baseline for new construction and additions, but it is not a gas ban — like-for-like replacements in existing homes follow the alteration rules. Expect the economics to keep shifting toward heat pump water heaters, especially where a 30-amp circuit is already in place.

How much does a HERS test cost if my project needs one?

Market data for Southern California puts a single HERS test visit at roughly $150 to $400, depending on the measures on your compliance documents and the number of systems. ERE doesn't do mystery pricing — call (310) 807-4800 with your CF1R and we'll give you a fixed quote.