2025 Single-Family Residential Water Heater Alterations

The 2025 Energy Code for single-family residential water heater alterations apply when altered or replacement service water-heating systems or components are installed and the requirements must meet Sections 150.2(b)1Hi, 150.2(b)1Hii, 150.2(b)1Hiiia, 150.2(b)1Hiiib, 150.2(b)1Hiiic, 150.2(b)H1iiid, and 150.2(b)2B.

Section 150.2(b)1Hi specifies when service water heating systems and parts or components are altered or replaced, the pipe insulation for newly installed or existing accessible pipes must meet the requirements of Section 150.0(j)1. Section 150.0(j)1A requires that all domestic hot water pipes must be insulated in accordance with Section 609.12 of the California Plumbing Code.

Section 150.2(b)1Hii specifies demand recirculation systems with manual on and off controls for recirculation distribution systems servicing individual dwelling units as required in the Reference Appendix RA4.4.9 of the 2025 Residential Appendices.

Section 150.2(b)1Hiii specifies the types of water heating systems that may be installed when service water-heating systems or components are altered or replaced. Options are:

• A natural gas or propane water-heating system; see Section 150.2(b)1Hiiia.
• A single heat pump water heater with a storage tank and meeting communication interface requirements; see Section 150.2(b)1Hiiib.
• A single heat pump water heater; see Northwest Energy Efficiency Alliance NEEA Advanced Water Heater Specification Tier 3 or higher, Section 150.21Hiiic.
• If the existing water heater is an electric resistance water heater; a consumer electric water heater, see Section 150.2(b)H1iiid. 

When a single heat pump water heater with a storage tank is installed, Section 150.2(b)1Hiiib specifies:

• The storage tank must be:
  • Placed on an incompressible and rigid insulated surface with at least a thermal resistance of R-10, and
  • Stored indoors.
• The installed water heater must have a communication interface in accordance with Section 110.12(a) or an American National Standards Institute (ANSI)/Consumer Technology Association (CTA)-2045-B communication port.

Section 150.2(b)H1iiid specifies that an existing electric resistance water heater must be a consumer electric water heater. A consumer electric water heater may be:

• An electric storage water heater,
• An electric instantaneous water heater, or
• A heat pump water heater.

Section 150.2(b)2B specifies that the standard design of an altered component must have a higher efficiency of existing conditions or requirements in accordance with Table 150.2-G. Table 150.2-G includes two options when existing conditions are:

• Verified by a certified Energy Code Compliance (ECC) Program -Rater, and
• Are not verified by a third party.

For unaltered components, the standard design is based on existing conditions. 

See the Blueprint and Single-Family Compliance Manual for more information, including articles and frequently asked questions about the 2025 Energy Code.