Title 24 · California Energy Code

Which appliance efficiency standards and test methods apply to water heaters?

Q: If a product has two test methods listed, can I choose the easier one?

No. The Energy Code requires compliance when tested with each listed test method; you must demonstrate the product meets the standard under every listed procedure. § 110.3(b).2

The California Energy Code requires that water heaters comply with the Appliance Efficiency Regulations — if multiple standards or test methods are listed for a water heater, the unit must meet every listed standard and be shown compliant when tested with each listed test method; verify via the Energy Commission certified‑appliances database per **§ 110.3(b)** and **§ 110.1**.

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Last reviewed: July 6, 2026

What the code requires — 2–4 sentences

The California Energy Code requires that service water-heating equipment meet the applicable requirements of the California Appliance Efficiency Regulations; this rule is stated in § 110.3(b). Equipment must meet all standards listed and must be tested to each test method listed where multiple methods are provided. The manufacturer’s certification and the Energy Commission certification directories are the means to verify compliance. § 110.3(b)

Equipment must comply with the Appliance Efficiency Regulations — if more than one standard or test method is listed for a water heater, the device must meet every listed standard and be shown compliant when tested using each listed test method. § 110.3(b)

Requirements in detail

Core rule (plain elements)

Equipment must “meet the applicable requirements of the Appliance Efficiency Regulations” as required by § 110.3(b). § 110.3(b)
If multiple standards are listed in the Appliance Efficiency Regulations for the same equipment, the equipment must meet all the standards listed. § 110.3(b).1
If multiple test methods are listed, the equipment must comply with the applicable standard when tested with each test method (i.e., test with each method and show compliance). § 110.3(b).2
Where equipment serves more than one function (for example space heating plus water heating), it must comply with the requirements applicable to each function. § 110.3(b).3

Defined terms you will see in compliance

Uniform Energy Factor (UEF) — the metric used to express overall water-heater efficiency and determined using the test methods identified in the Appliance Efficiency Regulations. UEF is a defined term in the Energy Code. § 110.3(b); UEF

How compliance is demonstrated / verified

Appliances regulated under Title 20 must be certified to the Energy Commission and are verified via the Energy Commission’s certified-appliance database or an approved directory per § 110.1. If test data are not available, the Commission-approved procedures apply. § 110.1

Quick decision table (decision‑relevant dimensions and where to look)

Decision factor	What the code requires (short)	Code Reference
Appliance falls under Title 20 Appliance Efficiency Regulations	Must meet the Appliance Efficiency Regulations applicable to that appliance	§ 110.3(b)
Multiple efficiency standards listed for same appliance	Appliance must meet all listed standards	§ 110.3(b).1
Multiple test methods listed	Appliance must show the applicable standard is met when tested with each listed test method	§ 110.3(b).2
Appliance that performs multiple functions (e.g., water + space heating)	Must comply with requirements for each function	§ 110.3(b).3
Verification of compliance	Use Energy Commission database or approved directories; certification by manufacturer required	§ 110.1
Metric for water‑heater efficiency	Use UEF as defined and measured by Appliance Efficiency Regulations	UEF definition and test reference

Test procedure interaction — practical note

Where the Appliance Efficiency Regulations list more than one test procedure (for the same declared metric), the Energy Code requires the appliance to demonstrate compliance under each such procedure — i.e., you cannot pick a single test method when multiple are listed. § 110.3(b).2

Exceptions & special cases

The manufacturer must certify compliance for installed equipment; the Energy Code allows verification through the Energy Commission’s database or an approved alternative directory per § 110.1. If data are not available through those directories, follow Commission-approved procedures. § 110.1
When a single piece of equipment serves multiple functions (e.g., combined water heating and space heating), compliance must be shown for each function separately, not just for the water‑heating side. § 110.3(b).3
Capacity-based requirements (for example provisions elsewhere that reference “maximum rated capacity”) are to be interpreted with respect to the equipment controls during steady‑state operation per § 110.3(b).4. § 110.3(b).4

Note: Specific prescriptive efficiency percent thresholds or UEF minimums are set in the Appliance Efficiency Regulations (Title 20) and in other referenced parts (for example certain high-capacity system rules in Appendix L/ASHRAE-derived requirements); those specific numeric thresholds must be read in the Appliance Efficiency Regulations or the referenced tables. The Energy Code text at § 110.3(b) sets the rule for which standards and test methods to apply, not the specific numeric minima. § 110.3(b)

Common mistakes

Assuming only one listed test method applies — if multiple test methods are listed the device must be tested to each method. § 110.3(b).2
Relying on a manufacturer declaration without confirming the appliance appears in the Energy Commission’s certified‑appliance database or approved directory as required by § 110.1. § 110.1
Overlooking multi‑function compliance: a combination unit that heats space and water must meet the requirements for both functions per § 110.3(b).3. § 110.3(b).3
Treating UEF as optional — UEF is the metric by which water‑heater efficiency is expressed and is determined according to the Appliance Efficiency Regulations; don’t substitute other metrics without confirming the Title 20 rules. UEF

Worked example — concrete scenario

Scenario: You are specifying a commercial gas instantaneous (tankless) water heater that the Appliance Efficiency Regulations list with (1) a thermal‑efficiency standard and (2) a UEF‑style numeric metric, and the Regulations reference two different test procedures A and B for those metrics.

Steps to show compliance:

Manufacturer must certify the product meets the applicable Appliance Efficiency Regulations for that equipment and submit certification to the Energy Commission. See § 110.1 and § 110.3(b). § 110.1 § 110.3(b)
Because the Appliance Efficiency Regulations list more than one standard, the appliance must meet both listed standards (for example, thermal efficiency threshold and UEF minimum) per § 110.3(b).1. § 110.3(b).1
Because the Regulations list two test methods, the manufacturer must demonstrate that the appliance meets the applicable standard when tested with each test method (i.e., run both test A and test B and show the appliance meets the numeric requirements under each). § 110.3(b).2
Confirm the appliance is listed in the Energy Commission certified‑appliances database (or approved directory) to verify compliance per § 110.1. § 110.1

Concrete numbers (example only where numbers come from the referenced tables): if the Appliance Efficiency Regulations require a minimum UEF of 0.85 and a thermal efficiency of 82% Et and list test methods X and Y, the heater must show UEF ≥ 0.85 when tested under X and under Y, and thermal efficiency ≥ 82% when tested under X and under Y, and be certified in the Energy Commission database. The Energy Code requires doing all the above per § 110.3(b) and verification under § 110.1. § 110.3(b) § 110.1

(If you need the exact numeric thresholds for a specific water‑heater model, consult the Title 20 Appliance Efficiency Regulations tables and the Energy Commission database; the Energy Code directs you to those sources for the actual numeric minima. § 110.3(b) )

Related provisions

§ 110.1 — Mandatory requirements for appliances; certification and verification process.
§ 110.3(c) — Installation and other service water‑heating system requirements (e.g., insulation, controls).
Appendix/Reference: L 503.4.3 (Appendix L / ASHRAE‑derived) — high‑capacity water‑heating system efficiency requirements (large systems).
Definition: Uniform Energy Factor (UEF) — metric used for water‑heater efficiency determination.

Code references

Grounded in the retrieved California Energy Code — click a citation to read the verbatim passage:

§ 110.3 High relevance — show source text
SECTION 110.3—MANDATORY REQUIREMENTS FOR SERVICE WATER-HEATING SYSTEMS AND EQUIPMENT

(a) Certification by manufacturers. Any service water- heating system or equipment may be installed only if the manufacturer has certified that the system or equipment complies with all of the requirements of this subsection for that system or equipment.
1. Temperature controls for service water-heating systems. Service water-heating systems shall be equipped with automatic temperature controls capable of adjustment from the lowest to the highest acceptable temperature settings for the intended use as listed in Table 3, Chapter 50 of the ASHRAE Handbook, HVAC Applications Volume or Table 613.1 of the Cali- fornia Plumbing Code for healthcare facilities. Exception to Section 110.3(a)1: Residential occupancies.
(b) Efficiency. Equipment shall meet the applicable requirements of the Appliance Efficiency Regulations as required by Section 110.1, subject to the following:
1. If more than one standard is listed in the Appliance Efficiency Regulations, the equipment shall meet all the standards listed; and
2. If more than one test method is listed in the Appliance Efficiency Regulations, the equipment shall comply with the applicable standard when tested with each test method; and
3. Where equipment can serve more than one function, such as both heating and cooling, or both space heating and water heating, it shall comply with all the requirements applicable to each function; and
4. Where a requirement is for equipment rated at its “maximum rated capacity” or “minimum rated capacity,” the capacity shall be as provided for and allowed by the controls, during steady-state operation.
(c) Installation. Any service water-heating system or equipment may be installed only if the system or equipment complies with all of the applicable requirements of this subsection for the system or equipment.
1. Outlet temperature controls. On systems that have a total capacity greater than 167,000 Btu/hr, outlets that require higher than service water temperatures as listed in the ASHRAE Handbook, Applications Volume, shall have separate remote heaters, heat exchangers or boosters to supply the outlet with the higher temperature. Exception to Section 110.3(c)1: Systems covered by California Plumbing Code Section 613.0 shall instead follow the requirements of that section.
2. Controls for hot water distribution systems. Service hot water systems with circulating pumps or with electrical heat trace systems shall be capable of automatically turning off the system. Exception to Section 110.3(c)2: Systems serving healthcare facilities.
3. Insulation. Unfired service water heater storage tanks and backup tanks for solar water-heating systems shall have: A. External insulation with an installed R -value of at least R-3.5; or
B. Internal and external insulation with a combined R -value of at least R-16; or

C. The heat loss of the tank surface based on an 80°F water-air temperature difference shall be less than 6.5 Btu per hour per square foot. 4. Water heating recirculation loops serving multiple dwelling units, high-rise residential, hotel/motel, and nonresiden- tial occupancies. A water heating recirculation loop is a type of hot water distribution system that reduces the time needed to deliver hot water to fixtures that are distant from the water heater, boiler or other water heating equipment. The recirculation loop is comprised of a supply portion, connected to branches that serve multiple dwelling units, guest rooms, or fixtures and a return portion that completes the loop back to the water heating equipment.
§ 207.3.2 High relevance — show source text
A6.207.3.2 Efficiency. Equipment shall meet the applicable requirements of the Appliance Efficiency Regulations as required by Section A6.210.1, subject to the following:
1. If more than one standard is listed in the Appliance Efficiency Regulations, the equipment shall meet all the standards listed; and
2. If more than one test method is listed in the Appliance Efficiency Regulations, the equipment shall comply with the applicable standard when tested with each test method; and
3. Where equipment can serve more than one function, such as both heating and cooling or both space heating and water heating, it shall comply with all the requirements applicable to each function; and
4. Where a requirement is for equipment rated at its “maximum rated capacity” or “minimum rated capacity,” the capacity shall be as provided for and allowed by the controls, during steady-state operation.
A6.207.3.3 Installation. Any service water-heating system or equipment may be installed only if the system or equipment complies with all of the applicable requirements of this subsection for the system or equipment.

A6.207.3.3.1 Outlet temperature controls. On systems that have a total capacity greater than 167,000 Btu/hr, outlets that require higher than service water temperatures as listed in the ASHRAE Handbook, Applications Volume, shall have separate remote heaters, heat exchangers or boosters to supply the outlet with the higher temperature.

A6.207.3.3.2 Temperature controls for public lavatories. The controls shall limit the outlet temperature to 110°F.

A6.207.3.3.3 Insulation. Unfired service water heater storage tanks and backup tanks for solar water-heating systems shall have:
1. External insulation with an installed R -value of at least R-12; or
2. Internal and external insulation with a combined R -value of at least R-16; or
3. The heat loss of the tank surface based on an 80°F water-air temperature difference shall be less than 6.5 Btu per hour per square foot.
A6.207.3.3.4 Service water heaters in state buildings. Any newly constructed building constructed by the State shall derive its service water heating from a system that provides at least 60 percent of the energy needed for service water heating from site solar energy or recovered energy.

Exception: Buildings for which the state architect determines that service water heating from site solar energy or recovered energy is economically or physically infeasible.

A6.207.4 Natural gas central furnaces, cooking equipment and pool and spa heaters: Pilot lights prohibited.

Any natural gas system or equipment listed below may be installed only if it does not have a continuously burning pilot light:
1. Fan-type central furnaces.
2. Household cooking appliances. Exception: Household cooking appliances without an electrical supply voltage connection and in which each pilot consumes less than 150 Btu/hr.
3. Pool heaters.
4. Spa heaters.
A6.207.5 Controls for space-conditioning systems. Space- conditioning systems shall be installed with controls that comply with the applicable requirements of Subsections A6.207.5.1 through A6.207.5.5.

A6.207.5.1 Thermostatic controls for each zone. The supply of heating and cooling energy to each space-conditioning zone or dwelling unit shall be controlled by an individual thermostatic control that responds to temperature within the zone and that meets the applicable requirements of Section A6.207.5.2.
§ 110.1 High relevance — show source text
SECTION 110.1—MANDATORY REQUIREMENTS FOR APPLIANCES

(a) Any appliance regulated by the Appliance Efficiency Regulations, Title 20 California Code of Regulations, Section 1601 et seq., may be installed only if the appliance fully complies with Section 1608(a) of those regulations.

(b) Except for those circumstances described in Section 110.1(c), conformance with efficiency levels required to comply with Part 6 mandatory, prescriptive and performance standards shall be verified utilizing data from either:
1. The Energy Commission’s database of certified appliances maintained pursuant to Title 20 California Code of Regulations Section 1606, and which is available at: www.energy.ca.gov/appliances/database/ ; or
2. An equivalent directory published by a federal agency; or
3. An approved trade association directory as defined in Title 20 California Code of Regulations Section 1606(h).
(c) Conformance with efficiency levels required to comply with Part 6 mandatory, prescriptive and performance standards shall be demonstrated either by default to the mandatory efficiency levels specified in Part 6 or by following procedures approved by the Commission pursuant to Section 10-109 of Title 24, Part 1, when:
1. Data to verify conformance with efficiency levels required to comply with Part 6 mandatory, prescriptive and performance standards is not available pursuant to subdivision (b); or
2. Field verification and diagnostic testing is required for compliance with Part 6 and the Energy Commission has not approved a field verification and diagnostic test protocol that is applicable to the appliance; or
3. The appliance meets the requirements of Section 110.1(a) but has been site-modified in a way that affects its performance; or
2025 CALIFORNIA ENERGY CODE 39

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

ALL OCCUPANCIES—MANDATORY REQUIREMENTS FOR THE MANUFACTURE, CONSTRUCTION AND INSTALLATION OF SYSTEMS, EQUIPMENT AND BUILDING COMPONENTS
1. The U.S. Department of Energy has approved a waiver from federal test procedures, pursuant to 10 CFR Section 430.27 or Section 431.401 and that waiver fails to specify how the efficiency of the system shall be determined.
Note: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code . Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.5 ~~, 2~~ 5402.8, and 25943, Public Resources Code.

SECTION 110.2—MANDATORY REQUIREMENTS FOR SPACE-CONDITIONING EQUIPMENT

Certification by manufacturers. Any space-conditioning equipment listed in this section may be installed only if the manufacturer has certified to the Commission that the equipment complies with all the applicable requirements of this section.

(a) Efficiency. Equipment shall meet the applicable efficiency requirements in Tables 110.2-A through 110.2-L, subject to the following:
1. If more than one efficiency standard is listed for any equipment in Tables 110.2-A through 110.2-L, the equipment shall meet all the applicable standards that are listed; and
2. If more than one test method is listed in Tables 110.2-A through 110.2-L, the equipment shall comply with the applicable efficiency standard when tested with each listed test method; and
§ 110.2 High relevance — show source text
Water-to-water heat pumps with a capacity less than 135,000 Btu/h are included in Table 110.2-B, Heat Pumps—Minimum Efficiency Requirements.
i. Source leaving liquid temperature.
1. The cooling evaporator liquid flow rate used for the heating rating for a reverse cycle air-to-water heat pump shall be the flow rate determined during the full load cooling rating.
2. The cooling evaporator liquid flow rate for the simultaneous cooling and heating and heat recovery liquid cooled chilling packages rating shall be the liquid flow rates
from the cooling operation full-load rating.
3. For heating-only fluid-to-fluid chiller packages, the evaporator flow rate obtained with an entering liquid temperature of 54°F and a leaving liquid temperature of 44°F
shall be used.
j. NA means the requirements are not applicable.|a. The size category is the full-load net refrigeration cooling mode capacity, which is the capacity of the evaporator available for cooling of the thermal load external to the chill-
ing package.
b. For air source heat pumps, compliance with both the 47°F and 17°F heating source outdoor air temperature (OAT) rating efficiency is required for heating.
c. Heating full-load rating conditions are at standard rating conditions defined in AHRI 550/590 (I-P), Table 4, includes the impact of defrost for air source heating ratings.
d. For units that operate in both cooling and heating, compliance with both the cooling and heating efficiency is required.
e. For heat recovery heating chilling package applications where there is simultaneous cooling and heating, compliance with the heating performance heat recover COPHR is
only required at one of the four heating AHRI 550/590 (I-P) standard ratings conditions of Low, Medium, Hot-Water 1 or Hot-Water 2. Compliance with the cooling-only perfor-
mance is required as defined in Notes b and c of Table 110.2-I.
f. For applications where the chilling package is installed to operate only in heating, compliance only with the heating performance COPH is required at only one of the heating
AHRI 550/590 (I-P) standard rating conditions of Low, Medium, High, or Boost. Compliance with cooling performance is not required.
g. For heat pump chilling package applications where the cooling capacity is not being used for conditioning, compliance with the heating performance COPH is only required at
one of the heating AHRI 550/590 (I-P) standard rating conditions of Low, Medium, High, or Boost. Compliance with the cooling performance is required as defined in Notes b
and c of Table 110.2-I, except as noted in Note f.
h. Water-to-water heat pumps with a capacity less than 135,000 Btu/h are included in Table 110.2-B, Heat Pumps—Minimum Efficiency Requirements.
i. Source leaving liquid temperature.
1. The cooling evaporator liquid flow rate used for the heating rating for a reverse cycle air-to-water heat pump shall be the flow rate determined during the full load cooling rating.
2. The cooling evaporator liquid flow rate for the simultaneous cooling and heating and heat recovery liquid cooled chilling packages rating shall be the liquid flow rates
from the cooling operation full-load rating.
3. For heating-only fluid-to-fluid chiller packages, the evaporator flow rate obtained with an entering liquid temperature of 54°F and a leaving liquid temperature of 44°F
shall be used.
j. NA means the requirements are not applicable.|a.

§ 2.10 High relevance — show source text

For SI units: 1000 British thermal units per hour = 0.293 kW

Notes: 1 ASHRAE 90.1 contains a complete specification of the referenced test procedure, including the referenced year version of the test procedure. 2 Combination units (i.e, furnaces contained within the same cabinet as an air conditioner) not covered by 10 CFR 430 [i.e., three-phase power or with cooling capacity greater than or equal to 65 000 Btu/h (19 kW)] may comply with either rating. All other units greater than 225 000 Btu/h (66 kW) sold in the U.S. must meet the AFUE standards for consumer products and test using USDOE’s AFUE test procedure at 10 CFR 430, Subpart B, Appendix N. 3 Compliance of multiple firing rate units shall be at the maximum firing rate. 4 Et = thermal efficiency. Units must also include an interrupted or intermittent ignition device (IID), have jacket losses not exceeding 0.75 percent of the input rating, and have either power venting or a flue damper. A vent damper is an acceptable alternative to a flue damper for those furnaces where combustion air is drawn from the conditioned space. 5 Ec = combustion efficiency (100 percent less flue losses). See test procedure for detailed discussion. 6 Units must also include an interrupted or intermittent ignition device (IID) and have either power venting or an automatic flue damper. 7 For U.S. applications of federal covered greater than 225 000 Btu/h (66 kW) products, see Informative Appendix F, Table F-4 of ASHRAE 90.1.

2025 CALIFORNIA MECHANICAL CODE 457

APPENDIX E

TABLE E 503.7.1(6) GAS- AND OIL-FIRED BOILERS ─ MINIMUM EFFICIENCY REQUIREMENTS

[ASHRAE 90.1: TABLE 6.8.1-6]

EQUIPMENT TYPE1	SUBCATEGORY OR RATING CONDITION	SIZE CATEGORY (INPUT)	MINIMUM EFFICIENCY9	EFFICIENCY AS OF 3/2/2022	TEST PROCEDURE
Boilers, hot water	Gas fired8	<300 000 Btu/h6, 7 for applications out- side U.S.9	82%AFUE	82%AFUE	Appendix N of 10 CFR Part 430
Boilers,

§ 25218.5 High relevance — show source text
(b) Certification Requirements for Manufactured Systems, Equipment, Appliances and Building Components.
1. Appliances that are within the scope of Section 1601 of the Appliance Efficiency Regulations shall only be installed if they have been certified to the Energy Commission by the manufacturer, pursuant to the provisions of Title 20 California Code of Regulations, Section 1606; or
2. Systems, equipment, appliances and building components that are required by Part 6 or the Reference Appendices to be certified to the Energy Commission, which are not appliances that are within the scope of Section 1601 of the Appliance Efficiency Regulations, shall only be installed if they are certified by the manufacturer in a declaration, executed under penalty of perjury under the laws of the State of California, that: A. All the information provided pursuant to the certification is true, complete, accurate and in compliance with all applicable requirements of Part 6; and B. The equipment, product, or device was tested using the test procedure specified in Part 6 if applicable
3. The certification status of any system, equipment, appliance or building component shall be confirmed only by reference to: A. A directory published or approved by the Commission; or B. A copy of the application for certification from the manufacturer and the letter of acceptance from the Commission staff; or C. Written confirmation from the publisher of a Commission-approved directory that a device has been certified; or D. A Commission-approved label on the device.
Note: Part 6 does not require a builder, designer, owner, operator, or enforcing agency to test any certified device to determine its compliance with minimum specifications or efficiencies adopted by the Commission.

Note: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code . Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.5 ~~, 2~~ 5402.8, and 25943, Public Resources Code.

SECTION 110.1—MANDATORY REQUIREMENTS FOR APPLIANCES

(a) Any appliance regulated by the Appliance Efficiency Regulations, Title 20 California Code of Regulations, Section 1601 et seq., may be installed only if the appliance fully complies with Section 1608(a) of those regulations.

(b) Except for those circumstances described in Section 110.1(c), conformance with efficiency levels required to comply with Part 6 mandatory, prescriptive and performance standards shall be verified utilizing data from either:
1. The Energy Commission’s database of certified appliances maintained pursuant to Title 20 California Code of Regulations Section 1606, and which is available at: www.energy.ca.gov/appliances/database/ ; or
2. An equivalent directory published by a federal agency; or
3. An approved trade association directory as defined in Title 20 California Code of Regulations Section 1606(h).
(c) Conformance with efficiency levels required to comply with Part 6 mandatory, prescriptive and performance standards shall be demonstrated either by default to the mandatory efficiency levels specified in Part 6 or by following procedures approved by the Commission pursuant to Section 10-109 of Title 24, Part 1, when:
1. Data to verify conformance with efficiency levels required to comply with Part 6 mandatory, prescriptive and performance standards is not available pursuant to subdivision (b); or
2. Field verification and diagnostic testing is required for compliance with Part 6 and the Energy Commission has not approved a field verification and diagnostic test protocol that is applicable to the appliance; or

§ 431.106 High relevance — show source text

2025 CALIFORNIA PLUMBING CODE 515

APPENDIX L

TABLE L 503.3.2 PERFORMANCE REQUIREMENTS FOR WATER-HEATING EQUIPMENT MINIMUM EFFICIENCY REQUIREMENTS (continued)

[ASHRAE 90.1: TABLE 7.8]

EQUIPMENT TYPE	SIZE CATEGORY (INPUT)	SUBCATEGORY OR RATING CONDITION	PERFORMANCE REQUIRED1	TEST PROCEDURE2,3
Pool heaters, gas	All	—	82%Et for commercial pool heaters and for applications out- side U.S. For U.S. applications, see foot- note (7).	Appendix P of 10 CFR 430
Heat pump pool heaters	All	50°F db 44.2°F wb Outdoor air 80.0°F entering water	4.0 COP	Appendix P of 10 CFR 430
Unfired storage tanks	All	—	R-12.5	(none)

For SI units: 1 gallon = 3.785 L, 1000 British thermal units per hour = 0.293 kW, °C = (°F-32)/1.8

Notes: 1 Thermal efficiency ( Et ) is a minimum requirement, while standby loss (SL) is a maximum requirement. In the SL equation, V is the rated volume in gallons and Q is the nameplate input rate in Btu/h (kW). Vm is the measured volume in the tank in gallons. Standby loss for electric water heaters is in terms of %/h and denoted by the term “S,” and standby loss for gas and oil water heaters is in terms of Btu/h and denoted by the term “SL.” Draw pattern (DP) refers to the water draw profile in the Uniform Energy Factor (UEF) test. UEF and Energy Factor (EF) are minimum requirements.

§ 505.0 High relevance — show source text
505.0 Oil-Burning and Other Water Heaters. 505.1 Water Heaters. Water heaters deriving heat from fuels or types of energy other than gas shall comply with the standards referenced in Table 501.1(1), Section 505.3, or Section 505.4. Vents or chimneys for such appliances shall be of approved types. An adequate supply of air for combustion and for adequate ventilation of heater rooms or compartments shall be provided. Each such appliance shall be installed in a

location approved by the Authority Having Jurisdiction and local and state fire-prevention agencies. 505.2 Safety Devices. Storage-type water heaters and hot water boilers deriving heat from fuels or types of energy other than gas, shall be provided with, in addition to the primary temperature controls, an over-temperature safety protection device that complies with and is installed in accordance with nationally recognized applicable standards for such devices and a combination temperature and pressure-relief valve.

505.3 Oil-Fired Water Heaters. Oil-fired water heaters

shall be installed in accordance with NFPA 31.

505.4 Indirect-Fired Water Heaters. Indirect-fired water heaters shall be in accordance with the applicable sections of the ASME Boiler and Pressure Vessel Code or shall comply with one of the other applicable standards shown in Table 501.1(1). Each water heater shall bear a label in accordance with ASME requirements, or an approved testing agency, certifying and attesting that such an appliance has been tested, inspected and meets the requirements of the applicable standards or code. 505.4.1 Single-Wall Heat Exchanger. An indirectfired water heater that incorporates a single-wall heat exchanger shall be in accordance with the following requirements:

(1) The heat transfer medium shall be either potable water or contain fluids recognized as safe by the Food and Drug Administration (FDA) as food grade.

(2) Bear a label with the word “Caution,” followed by the following statements:

(a) The heat-transfer medium shall be potable water or other nontoxic fluid recognized as safe by the FDA.

(b) The maximum operating pressure of the heat exchanger shall not exceed the maximum operating pressure of the potable water supply.

(3) The word “Caution” and the statements in letters shall have an uppercase height of not less than 0.120 of an inch (3.048 mm). The vertical spacing between lines of type shall be not less than 0.046 of an inch (1.168 mm). Lowercase letters shall be compatible with the uppercase letter size specification.

506.0 Air for Combustion and Ventilation.

506.1 General. Air for combustion, ventilation, and dilution of flue gases for appliances installed in buildings shall be obtained by application of one of the methods covered in Section 506.2 through Section 506.7.3. Where the requirements of Section 506.2 are not met, outdoor air shall be introduced in accordance with methods covered in Section 506.4 through Section 506.7.3.

Exception: This provision shall not apply to direct vent appliances. {NFPA 54:9.3.1.1} 506.1.1 Other Types of Appliances. Appliances of other than natural draft design, appliances not designated as Category I vented appliances, and appliances equipped with power burners shall be provided with combustion, ventilation, and dilution air in accordance with the appliance manufacturer’s instructions. [NFPA 54:9.3.1.2]
§ 110.1 High relevance — show source text
1(b), 110.1(c), Table 141.0-E, Table 150.2-D Requirements 110.2(a), Table 110.2D120.6(b)1G, Table 120.6-D Standard 110.2(a), Table 110.2-J Efficient Drift Eliminators 110.2(e) Egress 120.1(d), 130.1(a), 130.1(c)1, 6, 7, Table 130.5-B, 140.6(a)3K, 140.6(c)3H, 150.0(s)2, 150.1(c)4E, 160.2(c), 160.5(b)4, 170.2(e)2C, 4B Electric Clothes dryer 150.0(v), 160.9(c) Cooktop 150.0(u), 160.9(b) Demand 110.4(b) Furnace 110.2(d) Power distribution 160.6 Ready building 160.9 Reheat 141.0(a)2, 141.0(b)2C, 141.0(b)3, 180.2, 180.2(b)2B Resistance heating 110.4(a), 120.2(d), 120.6(a)2, 120.6(a)7, 140.4(g), 141.0(b)2C, 160.3(a)2, 170.2(c)4E Resistance space heat 141.0(b)2C, 150.2(b)1G, 180.2(b)2A, 180.2(b)2B Resistance water heater 150.2(b)1H, 180.2(b)3C Vehicle (EV) charger 110.10(b)1A, 110.10(b)1B Electrical Boxes 150.0(k)1, 160.5(a)1E Circuits 130.5(b), 130.5(d), 141.0(b)2P, Q, R, 160.6(b), 180.2(b)4B Energy monitoring 130.5(b), 141.0(b)2P, Q, R, 160.6(b), 180.2(b)4B Feeder 130.5(a), 141.0(b)2P, 160.6(a), 180.2(b)4B Input power 120.6(a)4G, 120.6(a)8H, 120.6(b)5H, 120.10(a), 140.4(c)1, 170.2(c)4A Load 130.2(c), Table 130.5-A, Table 130.5-B, 160.5(c)2, Table 160.6-A, Table 160.6-B Output 150.1(c)14, 170.2(f) Panel 110.9(c), 150.0(n), 160.4(a), 160.9(c) Power distribution system 100.0(b), 110.11, 120.6(h), 130.0, 130.5, 130.0(a), 141.0(a)1, 141.0(a)2, 141.0(b)2C, 141.0(b)2P, Q, R, 160.6(b), 180.1(a), 180.2(b)4 Receptacle 150.
§ 90.1 High relevance — show source text
In the UEF standard equations, Vr refers to the rated volume in gallons. 2 ASHRAE 90.1 contains a complete specification, including the year version, of the referenced test procedure. 3 Electric instantaneous water heaters with input capacity >40 946 Btu/h (12 kW) and ≤ 200 000 Btu/h (58.6 kW) must comply with the requirements for the 200 000 Btu/h (58.6 kW) if the water heater either: (a) has a storage volume >2 gallons (7.6 L); (b) is designed to provide outlet hot water at temperatures greater than 180°F (82°C); or (c) uses three phase power. 4 Gas storage water heaters with input capacity >75 000 Btu/h (22 kW) and ≤ 105 000 Btu/h (30.8 kW) must comply with the requirements for the >105 000 Btu/h (30.8 kW) if the water heater either: (a) has a storage volume >120 gallons (454 L); (b) is designed to provide outlet hot water at temperatures greater than 180°F (82.2°C); or (c) uses three-phase power 5 Oil storage water heaters with input capacity >105 000 Btu/h (30.8 kW) and ≤ 140 000 Btu/h (41.0 kW) must comply with the requirements for the >140 000 Btu/h (41.0 kW) if the water heater either (a) has a storage volume >120 gallons (454 L); (b) is designed to provide outlet hot water at temperatures greater than 180°F (82.2°C); or (c) uses three-phase power 6 Refer to Section L 503.4.3 for additional requirements for gas storage and instantaneous water heaters and gas hot-water supply boilers. 7 Water heaters or gas pool heaters in this category or subcategory are regulated as consumer products by the USDOE as defined in 10 CFR 430. 8 Where this standard is being applied to a building outside the U.S. and Canada and water heaters in this subcategory are being installed in that building, those water heaters shall meet the local efficiency requirements. If there are no local efficiency standards for residential water heaters, consideration should be given to using the USDOE efficiency requirements shown in Appendix F, Table F-2 of ASHRAE 90.1.

516 2025 CALIFORNIA PLUMBING CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE

APPENDIX M - PEAK WATER DEMAND CALCULATOR

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)
§ 13.3 High relevance — show source text
(1) The single space-heating boiler, or the component of a modular or multiple boiler system that is heating the service water, has a standby loss in Btu/h (kW) not exceeding (13.3 × pmd + 400)/ n, where ( pmd ) is the probable maximum demand in gallons per hour, determined in accordance with the procedures described in generally accepted engineering standards and handbooks, and ( n) is the fraction of the year where the outdoor daily mean temperature exceeds 64.9°F (18.28°C).

The standby loss is to be determined for a test period of 24 hours duration while maintaining a boiler water temperature of not less than 90°F (50°C) above ambient, with an ambient temperature

between 60°F (16°C) and 90°F (32°C). For a boiler with a modulating burner, this test shall be conducted at the lowest input. (2) It is demonstrated to the satisfaction of the Authority Having Jurisdiction that the use of a single heat source will consume less energy than separate units.

(3) The energy input of the combined boiler and water heater system is less than 150 000 British thermal units per hour (Btu/h) (44 kW). [ASHRAE 90.1:7.5.1] L 503.4.2 Service Water-Heating Equipment. Service water-heating equipment used to provide the additional function of space heating as part of a combination (integrated) system shall satisfy all stated requirements for the service water-heating equipment.

[ASHRAE 90.1:7.5.2] L 503.4.3 Large Service Water-Heating Systems. New buildings with service water-heating systems with a total installed input capacity of 1 000 000 Btu/h (293 kW) or greater, provided by high-capacity gas-fired service water-heating equipment shall meet either or both of the following requirements:

(1) Where a single unit of high-capacity gas-fired service water-heating equipment is installed, it shall have a minimum thermal efficiency ( Et ) of 92 percent. (2) Multiple units of high-capacity gas-fired service water-heating equipment connected to the same service water-heating system shall have a total input-capacity-weighted average thermal efficiency ( Et ) of at least 90 percent, and a minimum of 30 percent of the input of the high-capacity gas-fired service water-heating equipment in the service water heating-system shall have a thermal efficiency ( Et ) of at least 92 percent.

High-capacity gas-fired service water-heating equipment comprises gas-fired instantaneous water heaters with a rated input both greater than 200 000 Btu/h (58.6 kW) and not less than 4000 British thermal units per hour per gallon [Btu/(h•gal)] (0.3097 kW/L) of stored water, and gas-fired storage water heaters with a rated input both greater than 105 000 Btu/h (30.8 kW) and less than 4000 British thermal units per hour per gallon [Btu/(h•gal)] (0.3097 kW/L) of stored water.

Exceptions:

(1) Water heaters installed in individual dwelling units.
§ 140.4 High relevance — show source text
30 percent of the peak heat rejection of the cooling system; or B. 30 percent of SWHCAP.

Exception to Section 140.4(s): Buildings with a computer room heat recovery system or wastewater heat recovery system capable of providing not less than 25 percent of SWHCAP + HCAP.

Note: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code. Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.8, and 25943, Public Resources Code .

SECTION 140.5—PRESCRIPTIVE REQUIREMENTS FOR SERVICE WATER-HEATING SYSTEMS

(a) Nonresidential occupancies. Service water-heating systems in nonresidential buildings shall meet the requirements of 1 or 2 below, or meet the performance compliance requirements of Section 140.1:
1. School buildings less than 25,000 square feet and less than 4 stories in Climate Zones 2 through 15. A heat pump water-heating system that meets the applicable requirements of Sections 110.1, 110.3 and 120.3.
Exception to Section 140.5(a)1: A water-heating system serving an individual bathroom space may be an instantaneous electric water heater.
1. All other occupancies. A service water-heating system that meets the applicable requirements of Sections 110.1, 110.3, 120.3 and 140.5(c).
(b) Hotel/motel occupancies. A service water-heating system installed in hotel/motel buildings shall meet the requirements of Section 170.2(d).

(c) High-capacity service water-heating systems . Gas service water-heating systems with a total installed gas water-heating input capacity of 1 MMBtu/h or greater shall have gas service water-heating equipment with a minimum thermal efficiency of 90 percent. Multiple units can meet this requirement if the water-heating input provided by equipment with thermal efficiencies above and below 90 percent averages out to an input capacity-weighted average of at least 90 percent.

Exception 1 to Section 140.5(c): If 25 percent of the annual service water-heating requirement is provided by site-solar energy or site-recovered energy.

Exception 2 to Section 140.5(c): Water heaters installed in individual dwelling units.

Exception 3 to Section 140.5(c): Individual gas water heaters with input capacity at or below 100,000 Btu/h shall not be included in the calculations of the total system input or total system efficiency.

Note: Authority: Sections 25213, 25218, 25218.5, 25402 and 25402.1, Public Resources Code. Reference: Sections 25007, 25008, 25218.5, 25310, 25402, 25402.1, 25402.4, 25402.8, and 25943, Public Resources Code.

2025 CALIFORNIA ENERGY CODE 129

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

NONRESIDENTIAL AND HOTEL/MOTEL OCCUPANCIES—PERFORMANCE AND PRESCRIPTIVE

COMPLIANCE APPROACHES FOR ACHIEVING ENERGY EFFICIENCY

SECTION 140.6—PRESCRIPTIVE REQUIREMENTS FOR INDOOR LIGHTING

Frequently asked questions

What exactly does "meet the Appliance Efficiency Regulations" mean?

It means the water heater must satisfy the efficiency standards and be tested using the test procedures specified in the Appliance Efficiency Regulations (Title 20). The Energy Code requires meeting all listed standards and testing with each listed method. § 110.3(b)

How do I verify a water heater is compliant on a project?

Confirm the model is certified and listed in the Energy Commission’s certified‑appliances database or an approved directory as required by § 110.1. § 110.1

If a product has two test methods listed, can I choose the easier one?

No. The Energy Code requires compliance when tested with each listed test method; you must demonstrate the product meets the standard under every listed procedure. § 110.3(b).2

Does a combination water‑heating + space‑heating unit get a single compliance path?

No. A unit that serves multiple functions must comply with the requirements applicable to each function separately. § 110.3(b).3

Where are the numeric UEF or efficiency thresholds published?

Numeric thresholds are in the Appliance Efficiency Regulations (Title 20) and in referenced tables/appendices (e.g., Appendix L/ASHRAE tables). The Energy Code points you to those sources and requires following them. § 110.3(b)

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