This document, concerning residential and commercial water heaters, is a rulemaking 

action issued by the Department of Energy. Though it is not intended or expected, should 

any discrepancy occur between the document posted here and the document published in 

the Federal Register, the Federal Register publication controls. This document is being 

made available through the Internet solely as a means to facilitate the public's access to 

this document. 
 

 

 

 

 

[6450-01-P]
 

DEPARTMENT OF ENERGY
 

10 CFR Part 430
 

[Docket Number EERE-2011–BT–TP–0042]
 

RIN: 1904–AC53
 

Energy Conservation Program: Test Procedures for Residential Water Heaters and 

Commercial Water Heaters 

AGENCY: Office of Energy Efficiency and Renewable Energy, Department of Energy. 

ACTION: Request for Information. 

SUMMARY: Through this Request for Information (RFI), the U.S. Department of Energy 

(DOE) is initiating the rulemaking and data collection process to develop a uniform efficiency 

descriptor and accompanying test method for residential water heaters and commercial water 

heaters. This test procedure rulemaking is intended to fulfill DOE’s statutory obligation to 

develop a uniform efficiency descriptor for residential and commercial water heaters pursuant to 

the amendments to the Energy Policy and Conservation Act (EPCA) brought about by the 

American Energy Manufacturing Technical Corrections Act (AEMTCA; H.R. 6582), which was 

signed into law on December 18, 2012 (Pub. L. 112-210). To inform interested parties and to 

facilitate this process, DOE has identified several issues in this RFI on which DOE is particularly 

interested in receiving comment from interested parties. In overview, the issues outlined in this 

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document are mainly associated with: (1) currently available efficiency metrics and test 

procedures for rating the efficiency of residential and commercial water heaters; (2) the 

requirements for a uniform metric set forth in the AEMTCA; and (3) available options for DOE 

to address those statutory requirements. DOE welcomes written comments from the public on 

any subject within the scope of this rulemaking (including relevant topics not specifically raised 

in this RFI). 

DATES: Written comments and information are requested on or before [INSERT DATE 30 

DAYS AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER]. 

ADDRESSES: Interested persons are encouraged to submit comments using the Federal 

eRulemaking Portal at http://www.regulations.gov. Follow the instructions for submitting 

comments. Alternatively, interested persons may submit comments, identified by docket number 

EERE-2011-BT-TP-0042 and/or regulatory identification number (RIN) 1904-AC53, by any of 

the following methods: 

E-mail: HeatingProducts-2011-TP-0042@ee.doe.gov. Include EERE-2011-BT-TP-0042 

and/or RIN 1904-AC53 in the subject line of the message. Submit electronic comments 

in WordPerfect, Microsoft Word, PDF, or ASCII file format, and avoid the use of special 

characters or any form of encryption. 

Postal Mail: Ms. Brenda Edwards, U.S. Department of Energy, Building Technologies 

Program, Mailstop EE–2J, 1000 Independence Avenue, SW., Washington, DC 20585– 

0121. Telephone: (202) 586–2945. If possible, please submit all items on a compact disc 

(CD), in which case it is not necessary to include printed copies. 

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Hand Delivery/Courier: Ms. Brenda Edwards, U.S. Department of Energy, Building 

Technologies Program, 6th Floor, 950 L’Enfant Plaza, SW., Washington, DC 20024. 

Telephone: (202) 586–2945. If possible, please submit all items on a CD, in which case 

it is not necessary to include printed copies. 

Instructions: All submissions received must include the agency name and docket number 

or RIN for this rulemaking. No telefacsimilies (faxes) will be accepted. For detailed instructions 

on submitting comments and additional information on the rulemaking process, see section III of 

this document (Public Participation). 

Docket: For access to the docket to read background documents or comments received, 

go to the Federal eRulemaking Portal at http://www.regulations.gov. 

FOR FURTHER INFORMATION CONTACT: Requests for additional information may be 

sent to Mr. Mohammed Khan, U.S. Department of Energy, Office of Energy Efficiency and 

Renewable Energy, Building Technologies Program, Mailstop EE-2J, 1000 Independence 

Avenue, SW., Washington, DC 20585-0121. Telephone: (202) 586-7892. E-mail: 

Mohammed.Khan@ee.doe.gov. 

Mr. Eric Stas, U.S. Department of Energy, Office of the General Counsel, GC–71, 1000 

Independence Avenue, SW., Washington, DC 20585-0121. Telephone: (202) 586-9507. E-mail: 

Eric.Stas@hq.doe.gov. 

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For information on how to submit or review public comments, contact Ms. Brenda 

Edwards, U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, 

Building Technologies Program, EE-2J, 1000 Independence Avenue, SW., Washington, DC 

20585-0121. Telephone: (202) 586-2945. E-mail: Brenda.Edwards@ee.doe.gov. 

SUPPLEMENTARY INFORMATION: 

Table of Contents 

I. Introduction 

A. Authority and Background 

1. Residential Water Heaters 

2. Commercial Water Heaters 

B. The American Energy Manufacturing Technical Corrections Act (AEMTCA) 

II. Discussion 

A. Implications of the AEMTCA 

B. Potential Approaches to Address the Requirements of the AEMTCA 

1. Revised Energy Factor Metric 

2. Existing Thermal Efficiency and Standby Loss Metrics 

3. Revised Thermal Efficiency and Standby Loss Metrics 

4. Hybrid Efficiency Metric 

5. New Approach 

C. Conversion Factor 

D. Exclusions 

E. Other Concerns 

1. Representative Test Procedures 

2. Measures of Delivery Capacity 

3. Implications for Current Energy Conservation Standards 

III. Public Participation 

I. INTRODUCTION 

The American Energy Manufacturing Technical Corrections Act (AEMTCA), Pub. L. 

112-210, amended the Energy Policy and Conservation Act of 1975 (EPCA or the Act), Pub. L. 

94-163, to require that the U.S. Department of Energy (DOE or the Department) publish a final 

rule establishing a uniform efficiency descriptor and accompanying test methods for covered 

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residential water heaters and commercial water heating equipment within one year of the 

enactment of the AEMTCA.1 (42 U.S.C. 6295(e)(5)) Historically, DOE has administered its 

energy conservation standards (and specified the requisite test procedures) for residential water 

heaters and commercial water heaters separately. Thus, the historical background and statutory 

authority for these products are divided along those lines in the discussion that follows (i.e., 

sections I.A.1 and I.A.2). In addition, background information on the AEMTCA is presented in 

section I.B. 

A. Authority and Background 

1. Residential Water Heaters 

Residential water heaters are products that use oil, gas, or electricity to heat potable water 

for use outside the heater upon demand. These include storage type units, instantaneous type 

units, and heat pump type units.2 (42 U.S.C. 6291(27)) 

Title III, Part B3 of EPCA (42 U.S.C. 6291-6309, as codified) sets forth a variety of 

provisions designed to improve energy efficiency and establishes the Energy Conservation 

Program for Consumer Products Other Than Automobiles, which includes the residential water 

heaters that are, in part, the subject of today’s notice. (42 U.S.C. 6291(1)-(2) and 6292(a)(4)) 

1 The AEMTCA was signed into law on December 18, 2012, so accordingly, DOE must complete the required 

rulemaking by December 18, 2013. 

2 In a final rule published in the Federal Register on April 16, 2010, DOE determined that heat pump type water 

heaters with an integrated storage tank are a type of electric storage water heater, but that heat pump type water 

heaters without an integrated storage tank do not meet the definition of a “water heater” and are, therefore, not 

covered equipment under EPCA. 75 FR 20112, 20126 and 20135.
 3 This part was originally titled Part B. It was redesignated as Part A in the United States Code for editorial reasons.
 

5
 
 

 

 

 

 

 

 

This program authorizes DOE to establish technologically feasible, economically 

justified energy efficiency regulations for certain products and equipment that would be likely to 

result in substantial national energy savings. (42 U.S.C. 6295(o)(2)-(3)) Under EPCA, this 

program generally consists of four parts: (1) testing; (2) labeling; (3) establishing Federal energy 

conservation standards; and (4) certification and enforcement procedures. The testing 

requirements consist of test procedures that manufacturers of covered products must use as both 

the basis for certifying to DOE that their products comply with the applicable energy 

conservation standards adopted pursuant to EPCA, and for making representations about the 

efficiency of those products. (42 U.S.C. 6293(c); 42 U.S.C. 6295(s)) Similarly, DOE must use 

these test requirements to determine whether the products comply with any relevant standards 

promulgated under EPCA. (42 U.S.C. 6295(s)) 

Under 42 U.S.C. 6293 and 6314, EPCA sets forth criteria and procedures that DOE 

must follow when prescribing or amending test procedures for covered products and 

equipment. EPCA provides, in relevant part, that any test procedures prescribed or amended 

under this section must be reasonably designed to produce test results which measure energy 

efficiency, energy use, or estimated annual operating cost of a covered product during a 

representative average use cycle or period of use, and must not be unduly burdensome to 

conduct. (42 U.S.C. 6293(b)(3) and 6314(a)(2)) 

In addition, if DOE determines that a test procedure amendment is warranted, it must 

publish proposed test procedures and offer the public an opportunity to present oral and written 

comments on them. (42 U.S.C. 6293(b)(2) and 6314(b)) Also, in any rulemaking to amend a 

6
 
 

 

 

 

 

test procedure, DOE must determine the extent to which the proposed test procedure would 

alter the product’s measured energy efficiency. (42 U.S.C. 6293(e)(1)) If DOE determines 

that the amended test procedure would alter the measured efficiency of a covered product, 

DOE must amend the applicable energy conservation standard accordingly. (42 U.S.C. 

6293(e)(2)) 

Further, the Energy Independence and Security Act of 2007 (EISA 2007), Pub. L. 110­

140, amended EPCA to require that at least once every 7 years, DOE must review test 

procedures for all covered products and equipment and either amend the test procedures (if the 

Secretary determines that amended test procedures would more accurately or fully comply with 

the requirements of 42 U.S.C. 6293(b)(3) or 6314(a)(2)) or publish notice in the Federal Register 

of any determination not to amend a test procedure. (42 U.S.C. 6293(b)(1)(A) and 6314(a)(1)) 

The National Appliance Energy Conservation Act of 1987 (NAECA), Pub. L. 100-12, 

amended EPCA and established energy conservation standards for residential water heaters, as 

well as requirements for determining whether these standards should be amended. (42 U.S.C. 

6295(e)) Specifically, NAECA set minimum standards for residential water heaters in terms of 

the energy factor (EF) and required that DOE publish a final rule to determine whether the 

standard should be amended no later than January 1, 1992. (42 U.S.C. 6295(e)(1) and (4)(A)) It 

also required that DOE publish another final rule by January 1, 2000 to determine whether 

standards in effect for such products should again be amended. (42 U.S.C. 6295(e)(4)(B)) 

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Pursuant to 42 U.S.C. 6295(e)(4)(A), DOE published a final rule in the Federal Register 

on January 17, 2001 (hereafter referred to as the “January 2001 final rule”), amending 

statutorily-prescribed energy conservation standards for residential water heaters. 66 FR 4474. 

Compliance with the standards in the January 2001 final rule was required by January 20, 2004. 

Pursuant to 42 U.S.C. 6295(e)(4)(B), DOE published a final rule in the Federal Register on April 

16, 2010, amending the energy conservation standards for residential water heaters for a second 

time. 75 FR 20112. Compliance with the standards in the April 2010 final rule will be required 

beginning on April 16, 2015. The current and future energy conservation standards for 

residential water heaters are presented in Table I.1 immediately below. 

Table I.1 Energy Conservation Standards for Residential Water Heaters (10 CFR 

430.32(d)) 

Product Class Energy Factor (EF) as of 

January 20, 2004 

Energy Factor (EF) as of April 

16, 2015 

Gas-fired Storage EF = 0.67 - (0.0019 x Rated 

Storage Volume in gallons). 

For tanks with a Rated Storage 

Volume at or below 55 gallons: 

EF = 0.675 – (0.0015 x Rated 

Storage Volume in gallons). 

For tanks with a Rated Storage 

Volume above 55 gallons: 

EF = 0.8012 - (0.00078 x Rated 

Storage Volume in gallons). 

Electric Storage EF = 0.97 - (0.00132 x Rated 

Storage Volume in gallons). 

For tanks with a Rated Storage 

Volume at or below 55 gallons: 

EF = 0.960 – (0.0003 x Rated 

Storage Volume in gallons). 

For tanks for a Rated Storage 

Volume above 55 gallons: 

EF = 2.057 – (0.00113 x Rated 

Storage Volume in gallons). 

Oil-fired Storage EF = 0.59 – (0.0019 x Rated 

Storage Volume in gallons). 

EF = 0.68 – (0.0019 x Rated 

Storage Volume in gallons). 

Gas-fired 

Instantaneous 

EF = 0.62 – (0.0019 x Rated 

Storage Volume in gallons). 

EF = 0.82 – (0.0019 x Rated 

Storage Volume in gallons). 

Electric 

Instantaneous EF = 0.93 – (0.00132 × Rated Storage Volume in gallons). 

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Tabletop EF = 0.93 – (0.00132 × Rated Storage Volume in gallons). 

Note: The Rated Storage Volume equals the water storage capacity of a water heater, in gallons, as specified by the 

manufacturer. 

DOE’s test procedures for residential water heaters are found at 10 CFR 430.23(e) and 10 

CFR part 430, subpart B, appendix E, Uniform Test Method for Measuring the Energy 

Consumption of Water Heaters. The test procedures include provisions for determining the 

energy efficiency (EF), as well as the annual energy consumption of these products. 

The following provides a brief history of DOE’s more recent test procedure rulemakings 

related to residential water heaters. The current DOE test procedures for residential water 

heaters were established by a final rule published in the Federal Register on May 11, 1998 (63 

FR 25996), and subsequently updated through final rules published in July 1998 and January 

2001. (63 FR 38737 (July 20, 1998); 66 FR 4474 (Jan. 17, 2001)) The July 1998 final rule was 

a technical correction that added figures to the test procedure, and the January 2001 amendments 

added a definition to the test procedure, although the bulk of that final rule was dedicated to 

amended energy conservation standards for residential water heaters. On December 17, 2012, 

DOE published a final rule in the Federal Register, as required under 42 U.S.C. 6295(gg)(2), that 

concluded that no modifications were needed to the residential water heater test procedure to 

account for standby mode and off mode energy consumption, as the existing test procedure 

already accounted for those modes of energy consumption. 77 FR 74559. DOE initiated a 

rulemaking to consider updates to the water heater test procedure by publishing an RFI in the 

Federal Register on October 12, 2011 (hereafter referred to as the October 2011 RFI). 76 FR 

63211. 

2. Commercial Water Heaters 

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DOE’s regulations include the following types of commercial water heating equipment: 

(1) gas-fired, electric, and oil-fired commercial storage water heaters; (2) gas-fired and oil-fired 

instantaneous water heaters; (3) hot water supply boilers; and (4) unfired hot water storage tanks. 

10 CFR 431.2. Commercial storage type water heaters heat and store water within the appliance 

at a thermostatically-controlled temperature for delivery on demand; commercial storage type 

water heaters do not include units with an input rating of 4,000 Btu per hour or more per gallon 

of stored water. 10 CFR 431.102. Commercial instantaneous type waters heater include water 

heaters that have an input rating of at least 4,000 Btu per hour per gallon of stored water, 

including products meeting this description that are designed to heat water to temperatures of 

180° F or higher. Id. An unfired hot water storage tank is a tank used to store water that is 

heated externally. Id. DOE’s regulations further clarify that all such units are industrial 

equipment. Id. 

DOE’s regulations for commercial water heating equipment at 10 CFR 431.102 also 

include hot water supply boilers, which are a type of packaged boiler that is industrial equipment 

and that: 

(1) Has an input rating from 300,000 Btu/h to 12,500,000 Btu/h and of at least 4,000 

Btu/h per gallon of stored water, 

(2) Is suitable for heating potable water, and 

(3) Meets either or both of the following conditions: 

(i) It has the temperature and pressure controls necessary for heating potable water for 

purposes other than space heating, or 

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(ii) The manufacturer's product literature, product markings, product marketing, or 

product installation and operation instructions indicate that the boiler's intended 

uses include heating potable water for purposes other than space heating. 

Title III, Part C4 of EPCA (42 U.S.C. 6311-6317, as codified), added by Pub. L. 95-619, 

Title IV, §441(a), established the Energy Conservation Program for Certain Industrial 

Equipment, a program which addresses the energy efficiency of certain types of commercial and 

industrial equipment, including the commercial water-heating equipment that is, in part, the 

subject of this rulemaking. Relevant provisions of the Act specifically include definitions (42 

U.S.C. 6311), energy conservation standards (42 U.S.C. 6313), test procedures (42 U.S.C. 6314), 

labelling provisions (42 U.S.C. 6315), and the authority to require information and reports from 

manufacturers (42 U.S.C. 6316). 

The Energy Policy and Conservation Act of 1992 (EPACT 1992), Pub. L. 102-486, 

amended EPCA and established energy conservation standards for commercial storage water 

heaters, instantaneous water heaters, and unfired water storage tanks. (42 U.S.C. 6313(a)(5)) 

Specifically, EPACT 1992 set standards for various types of commercial water heating 

equipment in terms of minimum thermal efficiency (Et) and maximum standby loss (SL), based 

on the type of fuel used, the type of unit (e.g., storage type or instantaneous type), and the input 

capacity. The standard levels generally corresponded to the levels in the American Society of 

Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) Standard 90.1, Energy 

Standard for Buildings Except Low-Rise Residential Buildings, as in effect on October 24, 1992 

(i.e., ASHRAE Standard 90.1-1989). In acknowledgement of technological changes that yield 

4 For editorial reasons, upon codification in the U.S. Code, Part C was redesignated Part A-1. 

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energy efficiency benefits, Congress further directed DOE through EPCA to consider amending 

the existing Federal energy conservation standard for commercial water heating equipment, each 

time ASHRAE Standard 90.1 is amended with respect to such equipment. (42 U.S.C. 

6313(a)(6)(A)) EPCA also requires that if a test procedure referenced in ASHRAE Standard 

90.1 is updated, DOE must update its test procedure to be consistent with the amended test 

procedure, unless DOE determines that the amended test procedure is not reasonably designed to 

produce test results which reflect the energy efficiency, energy use, or estimated operating costs 

of the ASHRAE equipment during a representative average use cycle. In addition, DOE must 

determine that the amended test procedure is not unduly burdensome to conduct. (42 U.S.C. 

6314(a)(2) and (4)) 

Pursuant to the requirements of EPCA, DOE last amended the energy conservation 

standards for commercial water heating equipment in a final rule published in the Federal 

Register on January 12, 2001. 66 FR 3336. The amended energy conservation standards largely 

corresponded to the levels contained in ASHRAE Standard 90.1-1999. In a direct final rule 

published in the Federal Register on October 21, 2004, DOE prescribed test procedures to rate 

the energy efficiency of commercial water heaters and hot water supply boilers, specifying 

definitions for these products as well as unfired hot water storage tanks. 69 FR 61974. The rule 

also recodified existing energy conservation standards to locate them in closer proximity in the 

CFR to the test procedures that DOE promulgated. The current standards for commercial water 

heating equipment are set forth at 10 CFR 431.110 and shown in Table I.2 below. 

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Table I.2 Energy Conservation Standards for Commercial Water Heating Equipment (10 

CFR 431.110) 

Product Size 

Energy conservation standard* (products 

manufactured on and after October 29, 2003)** 

Minimum thermal 

efficiency Maximum standby loss*** 

Electric storage water heaters All N/A 0.30 + 27/Vm(%/hr) 

Gas-fired storage water heaters ≤155,000 

Btu/hr 

>155,000 

Btu/hr 

80% 

80% 

Q/800 + 110(Vr) 1/2(Btu/hr) 

Q/800 + 110(Vr) 1/2(Btu/hr) 

Oil-fired storage water heaters ≤155,000 

Btu/hr 

>155,000 

Btu/hr 

78% 

78% 

Q/800 + 110(Vr) 1/2(Btu/hr) 

Q/800 + 110(Vr) 1/2(Btu/hr) 

Gas-fired instantaneous water 

heaters and hot water supply 

boilers 

<10 gal 

≥10 gal 

80% 

80% 

N/A 

Q/800 + 110(Vr) 1/2(Btu/hr) 

Oil-fired instantaneous water 

heaters and hot water supply 

boilers 

<10 gal 

≥10 gal 

80% 

78% 

N/A 

Q/800 + 110(Vr) 1/2(Btu/hr) 

Product Size Minimum thermal insulation 

Unfired hot water storage tank All R-12.5 

* Vm is the measured storage volume and Vr is the rated volume, both in gallons. Q is the nameplate input rate in 

Btu/h. 

** For hot water supply boilers with a capacity of less than 10 gallons: (1) the standards are mandatory for products 

manufactured on and after October 21, 2005, and (2) products manufactured prior to that date, and on or after 

October 23, 2003, must meet either the standards listed in this table or the applicable standards in subpart E of this 

part for a “commercial packaged boiler.” 

*** Water heaters and hot water supply boilers having more than 140 gallons of storage capacity need not meet the 

standby loss requirement if: (1) the tank surface area is thermally insulated to R-12.5 or more, (2) a standing pilot 

light is not used and (3) for gas or oil-fired storage water heaters, they have a fire damper or fan-assisted 

combustion. 

DOE’s test procedures for commercial water heaters (other than commercial heat pump 

water heaters) are found at 10 CFR 431.106 and as noted previously, were established in an 

October 21, 2004 direct final rule. 69 FR 61974. The test procedures for commercial water 

heating equipment are currently largely based on American National Standards Institute (ANSI) 

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Z21.10.3-1998, Gas Water Heaters – Volume III, Storage Water Heaters with Input Ratings 

Above 75,000 Btu Per Hour, Circulating and Instantaneous. The test procedures include 

provisions for determining thermal efficiency and standby loss. DOE published a final rule in 

the Federal Register on May 16, 2012 that amended the test procedures for commercial water 

heating equipment to reference the most current industry standard (i.e., ANSI Z21.10.3-2011). 

77 FR 28928. Compliance with the amended test procedures is required beginning on May 13, 

2013. 

B. The American Energy Manufacturing Technical Corrections Act (AEMTCA) 

The AEMTCA amended EPCA to require that DOE publish a final rule establishing a 

uniform efficiency descriptor and accompanying test methods for covered water heaters (both 

residential and commercial) not later than one year after the enactment of the AEMTCA. (42 

U.S.C. 6295(e)(5)(B)) The final rule must replace the current EF, Et , and SL metrics with a 

uniform efficiency descriptor. (42 U.S.C. 6295(e)(5)(C)) Further, the AEMTCA requires that 

beginning one year after the date of publication of DOE’s final rule establishing the uniform 

descriptor, the efficiency standards for covered water heaters must be denominated according to 

the uniform efficiency descriptor established in the final rule (42 U.S.C. 6295(e)(5)(D)), and that 

DOE must develop a mathematical conversion factor for converting the measurement of 

efficiency for covered water heaters from the test procedures and metrics currently in effect (i.e., 

EF for residential water heaters and Et and SL for commercial water heaters) to the new uniform 

energy descriptor. (42 U.S.C. 6295(e)(5)(E)(ii)) Such conversion factor would apply to affected 

water heaters that are tested prior to the establishment of the final rule. The AEMTCA requires 

that the conversion factor not affect the minimum efficiency requirements for covered water 

heaters. (42 U.S.C. 6295(e)(5)(E)(iii)) Covered water heaters shall be considered to comply 

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with the final rule on and after the effective date of the final rule and with any revised labeling 

requirements established by the Federal Trade Commission to carry out the final rule if the 

covered water heater was manufactured prior to the effective date of the final rule and complied 

with the efficiency standards and labeling requirements in effect prior to the final rule. (42 

U.S.C. 6295(e)(5)(K)) 

The AEMTCA requires that the uniform efficiency descriptor and accompanying test 

method apply, to the maximum extent practicable, to all water heating technologies currently in 

use and to future water heating technologies. (42 U.S.C. 6295(e)(5)(H)) However, the 

AEMTCA allows DOE to provide an exclusion from the uniform efficiency descriptor for any 

specific category of otherwise covered water heaters that do not have a residential use, that can 

be clearly described, and that are effectively rated using the current thermal efficiency and 

standby loss descriptors. (42 U.S.C. 6295(e)(5)(F)) 

The AEMTCA also outlines DOE’s options in terms of establishing a new uniform 

efficiency descriptor for water heaters. Specifically, the options provided to DOE for a uniform 

descriptor include: (1) a revised version of the energy factor descriptor currently in use; (2) the 

thermal efficiency and standby loss descriptors currently in use; (3) a revised version of the 

thermal efficiency and standby loss descriptors; (4) a hybrid of descriptors; or (5) a new 

approach. (42 U.S.C. 6295(e)(5)(G)) Each of these options is discussed in further detail in 

section II.B. 

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Lastly, the AEMTCA also requires that DOE invite interested stakeholders to participate 

in the rulemaking process used to establish the final rule (42 U.S.C. 6295(e)(5)(I)), and that DOE 

contract with the National Institute of Standards and Technology (NIST), as necessary, to 

conduct testing and simulation of alternative descriptors identified for consideration (42 U.S.C. 

6295(e)(5)(J)) 

In response to the statutory provisions of the AEMTCA, DOE envisions developing an 

energy efficiency metric (or metrics) that covers all residential and commercial water heaters. 

Such metric (or metrics) would be determined through a test method that is as uniform as 

possible while still producing a rating that is representative of performance under conditions that 

approximate actual usage. Additionally, DOE will strive to develop a uniform test method that 

would minimize incremental test burdens on manufacturers to the extent possible. 

II. DISCUSSION 

A. Implications of the AEMTCA 

DOE tentatively interprets the relevant provisions of the AEMTCA to mean that a single 

efficiency metric and test method should apply to all water heaters currently covered under 

residential and commercial test methods unless circumstances justify use of the exclusion 

provided under 42 U.S.C. 6295(e)(5)(F). This interpretation means that water heaters from the 

smallest capacity and size rating used in residential applications all the way up to the largest 

capacity covered under DOE’s commercial water heater program should be subject to the same 

rating metric and testing procedures. These test methods and the resulting uniform rating metric 

should cover all fuel types and technologies, including storage water heaters, instantaneous water 

heaters, integral heat pump water heaters, non-integral heat pump water heaters, unfired hot 

16
 
 

 

 

 

 

 

 

 

 

water storage tanks, and hot water supply boilers. In addition, DOE believes it may be 

appropriate for the uniform descriptor and test methods to also address hot water supply boilers, 

which are included with other types of commercial water heating equipment in DOE’s 

regulations at 10 CFR 431.110, although they are not explicitly called out among the covered 

products in 42 U.S.C. 6295(e)(5)(A). DOE is interested in receiving comment on whether the 

uniform efficiency descriptor should apply to all types of residential and commercial water 

heaters covered by EPCA, hot water supply boilers, and unfired hot water storage tanks. Lastly, 

DOE acknowledges that the AEMTCA provides for the possibility of an exclusion for certain 

water heaters from the uniform efficiency metric and accompanying test method (42 U.S.C. 

6295(e)(5)(F) and further discusses this exclusion below in section II.D. 

B. Potential Approaches to Address the Requirements of the AEMTCA 

As noted previously, the AEMTCA provides five options by which DOE can meet the 

relevant requirements related to water heaters. (42 U.S.C. 6295(e)(5)(G)) Each of these options 

is discussed for comment in the sections that immediately follow. 

1. Revised Energy Factor Metric 

Energy factor is currently the regulating metric for residential water heaters. Energy 

factor is a measure of the overall efficiency of the water heater and accounts for efficiency 

during active, standby, and cyclical operation. DOE’s test method for determining energy factor 

currently includes a 24-hour simulated use test consisting of six hot water draws followed by a 

standby period. 10 CFR part 430, subpart B, appendix E. 

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DOE has tentatively decided that the revised energy factor approach would follow the 

general technique for determining energy factor that is currently in place for residential water 

heaters. The current approach provides the efficiency of the water heater over a defined period 

of time (currently 24 hours) subject to a specified usage profile and ambient conditions. Based 

on comments received in response to the October 2011 RFI (76 FR 63211), DOE believes that a 

24-hour simulated-use test is the most viable method for obtaining the energy factor for 

residential water heaters. 

Advantages of such an approach are that it results in a single descriptor that is clear and 

concise for evaluating the efficiency of a water heater and that it is applicable across all fuel 

types, sizes, and technologies. All water heaters would be subject to a simulated-use test that is 

similar to the test currently required for residential water heaters. The simulated-use test 

provides a means by which the water heater’s efficiency is determined under a pattern of 

representative usage. A properly designed simulated-use test can also be technologically 

agnostic, meaning that the test applies to water heaters utilizing any water heating technology 

and that it would properly represent the efficiency of one technology versus another for a 

particular application. 

A disadvantage of the current simulated-use test is that it requires assumptions of in-field 

usage, and a single use pattern as currently applied in the residential test procedure would not be 

appropriate for the wide range of water heaters covered under this legislation. The October 2011 

RFI requested comments on the appropriateness of the draw pattern. 76 FR 63211, 63214 (Oct. 

12, 2011). Among the comments, some mentioned the need to implement multiple draw patterns 

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appropriate for different size classes. This technique may provide more appropriate demands for 

a range of water heaters, and allow for an accurate representation of efficiency of a wide range of 

different water heaters, including those that are currently rated as commercial units. However, 

one potential disadvantage of using multiple, differing draw patterns would be the increased 

complexity of a simulated-use test and the added test time. 

In addition to comments on the appropriateness of a simulated-use test approach, DOE 

also seeks comment on draw patterns that could be used in extending such an approach to water 

heaters intended for the commercial market. 

2. Existing Thermal Efficiency and Standby Loss Metrics 

Thermal efficiency and standby loss are currently the regulating metrics for commercial 

water heating equipment, with the exception of unfired storage tanks which are regulated by 

minimum thermal insulation. Thermal efficiency accounts for the efficiency of a water heater 

during active operation, while standby loss accounts for efficiency during standby periods. 

DOE’s test methods for determining thermal efficiency and standby loss reference the industry 

standard, ANSI Z21.10.3, and are specified at 10 CFR 431.106. 

DOE has tentatively decided that this option would use the thermal efficiency and 

standby loss metrics and test methods that are currently in place for the commercial water 

heating equipment for all covered water heaters, including residential units that are currently 

rated using energy factor. 

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The key advantage of this approach is that the tests would be simpler to implement. No 

changes would be needed to the commercial water heaters test method, because that same test 

procedure, as it exists today, could be applied to both residential and commercial models. While 

this may be true from a technical perspective, there may be disadvantages in terms of 

characterizing representative use, as explained below. 

A disadvantage of this approach is that it does not account for energy efficiency 

performance during cyclical portions of water heater operation. Comments to the October 2011 

RFI (76 FR 63211) indicated that field data show lower efficiency in the actual use compared to 

the rating obtained using the current DOE simulated use test because of cycling of the units 

between warm and cold states under usage typically seen in residences. The thermal efficiency 

is a measure of efficiency during the water delivery stage, and the standby loss factor is a 

measure of efficiency during the standby mode stage. Neither of these metrics would capture the 

losses associated with cyclical warm-up and cool-down of water heaters. It is also questionable 

whether thermal efficiency is an appropriate metric for smaller storage water heaters, because 

they are not designed to provide a large supply of hot water continuously. It should also be 

noted that the test procedure for residential water heaters utilized the thermal efficiency and 

standby loss tests up until 1990, when a simulated use test was adopted to make the test uniform 

across technologies, particularly for heat pump water heaters and gas instantaneous water 

heaters. 

3. Revised Thermal Efficiency and Standby Loss Metrics 

DOE has tentatively decided that this approach would be a modified version of the 

current commercial water heater test procedure that results in the same descriptors, albeit with 

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potentially modified meanings, as those currently used to rate commercial water heaters. One 

option would be to use a metric similar to the recovery efficiency and standby heat loss 

coefficient as computed in the current residential water heater test procedure. 

The advantage of such an approach is that simpler laboratory tests that are more 

repeatable could theoretically be used to rate efficiency. Revisions to the original metrics and 

test methods, such as changes to account for cycling effects, changes to the water delivery 

temperature, and ambient conditions, could make them more suitable for residential water 

heaters compared to the existing metrics. 

Disadvantages with this approach are the same as those discussed above in section II.B.2 

for the existing thermal efficiency and standby loss metrics. Most notably, it is not clear that 

these metrics would capture efficiency effects of cycling water heaters on and off. Additionally, 

DOE is not aware of any proposed approaches other than those discussed related to the 

residential water heater test method incorporating revised thermal efficiency and standby loss 

descriptors, nor is it aware of what specifically can be done to revise or improve thermal 

efficiency and standby loss to accomplish the intent of the AEMTCA. 

4. Hybrid Efficiency Metric 

DOE has tentatively decided that this approach would involve a combination of the 

current energy factor, thermal efficiency, and standby loss metrics into a new single uniform 

descriptor. DOE anticipates that such a metric would utilize some combination of the existing 

test procedures and aspects of the existing metrics to obtain information for the new hybrid 

metric. 

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The advantage of such an approach is that parts or all of existing test methods could be 

utilized, thereby decreasing the effort for manufacturers and testing agencies in developing test 

programs even if certain portions of those test methods had not been previously applied to all 

models of water heaters. 

The disadvantage of such an approach could be that it would require more tests on each 

water heater if each water heater should need to undergo a test to determine multiple individual 

metrics that ultimately result in a single, hybrid metric, resulting in a higher burden on 

manufacturers. The testing method to obtain a uniform “hybrid” metric may lead to biases 

between different water heating technologies if the performance model fails to capture critical 

aspects of a particular technology’s operation. This model may also require adjustment as new 

technologies emerge. Furthermore, DOE is not aware of any proposed approaches towards 

developing a hybrid metric, nor what specifically could be done by a hybrid metric to accomplish 

the intent of the AEMTCA. 

5. New Approach 

DOE seeks comment on any other approach or descriptor that it should consider that has 

not previously been discussed. 

C. Conversion Factor 

The AEMTCA requires that DOE develop a temporary mathematical conversion factor 

for converting the measurement of efficiency for covered water heaters from the existing test 

procedures to the new energy descriptor established under the final rule. (42 U.S.C. 

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6295(e)(5)(E)) The allowance to use the conversion factor will expire 1 year after publication of 

such conversion factor or December 31, 2015, whichever is later. (42 U.S.C. 6295(e)(5)(E)(v)) 

The form and magnitude of this mathematical conversion factor would depend on which option 

is chosen, and on the extent of accompanying test procedure modifications. Thus, particularly 

for comments related to new or adjusted metrics, DOE seeks comment on ways to convert from 

the existing metrics for the different types of residential and commercial water heaters to the 

uniform metric, as discussed above. 

D. Exclusions 

The AEMTCA indicates that the final rule may exclude a specific category of covered 

water heaters from the uniform efficiency descriptor, if such category of water heaters: (1) does 

not have a residential use and can be clearly described in the final rule; and (2) can be effectively 

rated using the existing thermal efficiency and standby loss descriptors. (42 U.S.C. 

6295(e)(5)(F)) Tentatively, DOE does not view the exclusion as applying to all models that are 

solely offered for non-residential applications, and the Department notes that the statute states 

that DOE’s final rule may exclude certain types of water heaters. Moreover, under 42 U.S.C. 

6295(e)(5)(H), the AEMTCA states that “[t]he efficiency descriptor and accompanying test 

method established under the final rule shall apply, to the maximum extent practicable, to all 

water heater technologies in use... and to future water heater technologies.” If DOE were to 

review the exclusion in a broad manner, it would apply to a large subset of models that currently 

are characterized as commercial water heaters under DOE’s regulatory scheme. In addition, it is 

unclear how the Department could create an equitable distinction for application of the exclusion 

based on a manufacturer’s claim of intended use of its product. DOE also notes that no other 

statutory section specifically indicates that the uniform descriptor should only apply to water 

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heaters intended for residential use, and thus, DOE believes the uniform descriptor should apply 

to all covered water heaters, unless a clear need exists and the statutory criteria for using the 

exclusion are met. It is DOE’s position that an expansive view of the above-referenced 

exclusion authority would largely undermine the purposes of AEMTCA in terms of achieving a 

uniform efficiency metric and test method for all water heaters. 

With the above understanding in mind, DOE has tentatively concluded that a uniform 

efficiency descriptor and test method would be possible for all water heaters covered by the 

statute, but DOE seeks comment on the types of water heaters, if any, that should be excluded, 

along with a rationale to support such exclusion. (42 U.S.C. 6295(e)(5)(F)) As an example, DOE 

notes that unfired storage tanks and commercial “add-on” heat pump water heaters (which are 

typically shipped without tanks and the paired with a storage tank or storage water heater) are not 

completely contained water heating systems, and are required to be paired with other water 

heating equipment in the field to operate as intended. As such, these types of equipment have 

specific characteristics that may not be conducive to a uniform efficiency metric, and certain 

efficiency metrics may not be applicable to these types of equipment depending on the testing 

requirements for that metric. DOE requests comment on whether these types of equipment 

should be excluded from the uniform efficiency descriptor requirement. 

If stakeholders were to suggest that DOE exclude certain heaters that do not have a 

residential use, comments are sought as to how to distinguish those water heaters based on 

characteristics of the products. DOE would be interested in comments regarding whether the 

storage volume, energy input capacity, output capacity as determined through testing, or another 

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means would be appropriate for indicating which water heaters clearly do not have a residential 

use and are effectively rated under current procedures. 

At this point, the Department tentatively expects the exclusions, if any, to be limited in 

number. DOE seeks comments on the characteristics of any types of water heaters that should be 

excluded from this uniform efficiency descriptor, as well as the rationale for doing so. 

E. Other Concerns 

DOE seeks comments on any other issues that may relate to the development of a 

uniform efficiency descriptor and test methods, and the requirements of the AEMTCA. In 

particular, DOE has identified several additional issues below for discussion. 

1. Representative Test Procedures 

As noted above, under 42 U.S.C. 6293 and 6314, EPCA sets forth the criteria and 

procedures DOE must follow when prescribing or amending test procedures for covered products 

and equipment. EPCA provides, in relevant part, that any test procedures prescribed or amended 

under this section must be reasonably designed to produce test results which measure energy 

efficiency, energy use, or estimated annual operating cost of a covered product during a 

representative average use cycle or period of use, and must not be unduly burdensome to 

conduct. (42 U.S.C. 6293(b)(3) and 6314(a)(2)) Usage patterns between water heaters intended 

for residential applications and those intended for commercial applications, however, are vastly 

different, as dictated by factors such as water delivery temperature, flow rate, total volume of 

water delivered per day, and draw pattern. In addition, environmental factors that could affect 

performance (e.g., such as ambient air temperature, ambient relative humidity, and inlet water 

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temperature) may also vary. DOE seeks comments on the best approaches to managing these 

wide ranges of conditions for testing purposes, while still meeting the requirements of EPCA to 

produce energy efficiency results during a representative period of use and not be unduly 

burdensome to conduct. 

2. Measures of Delivery Capacity 

The current DOE residential water heater test procedure requires a test to measure the 

delivery capacity of the water heater, resulting in either a first-hour rating for storage water 

heaters or a maximum gallons-per-minute rating for instantaneous water heaters. No equivalent 

test for delivery capacity is present for commercial water heaters. DOE seeks comments on the 

need for this metric for water heaters intended for non-residential applications. Additionally, 

DOE seeks comments regarding the applicability of the metrics and test methods currently 

present in the residential water heater test procedure (first-hour rating, maximum gallons-perminute) for commercial water heaters. 

3. Implications for Current Energy Conservation Standards 

In developing the uniform efficiency descriptor, the AEMTCA requires that DOE 

develop a mathematical conversion factor (discussed in section II.C) for converting the 

measurement of efficiency for covered water heaters under the current test procedures to the 

uniform descriptor. The AEMTCA stipulates that the conversion factor shall not affect the 

minimum efficiency requirements for covered water heaters. 

To address this requirement, DOE plans to develop a conversion factor as discussed in 

section II.C and apply it to the current energy conservation standards to equate the standards 

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under the existing metric and test procedures to the standards using the new uniform efficiency 

metric and test procedures. DOE requests comment on this approach to maintaining equivalent 

efficiency standards, and on the appropriate approach to develop the mathematical conversion. 

III. PUBLIC PARTICIPATION 

DOE invites all interested parties to submit in writing by [INSERT DATE 30 DAYS 

AFTER DATE OF PUBLICATION IN THE FEDERAL REGISTER], comments and 

information on matters addressed in this notice and on other matters relevant to DOE’s 

consideration of a uniform efficiency descriptor and accompanying test methods for residential 

and commercial water heaters. 

After the close of the comment period, DOE will begin collecting data, conducting the 

relevant analyses, and reviewing the public comments. These actions will be taken to aid in the 

development of a test procedure NOPR for residential and commercial water heaters that 

establishes a uniform efficiency descriptor and accompanying test method. 

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