3-i

CHAPTER 3.MARKET AND TECHNOLOGY ASSESSMENT

TABLE OF CONTENTS

3.1 INTRODUCTION ........................................................................................................... 3-1

3.1.1 Product Definitions and Scope of Coverage.................................................................... 3-1

3.1.2 Test Procedure ................................................................................................................. 3-3

3.2 MARKET ASSESSMENT.............................................................................................. 3-4

3.2.1 Trade Association ............................................................................................................ 3-4

3.2.2 Manufacturers and Market Share..................................................................................... 3-4

3.2.3 Potential Small Business Impacts.................................................................................... 3-6

3.2.4 Distribution Channels...................................................................................................... 3-6

3.2.5 Regulatory Programs ....................................................................................................... 3-7

3.2.6 Non-Regulatory Programs............................................................................................... 3-9

3.2.7 Product Lifetime ............................................................................................................ 3-10

3.2.8 Market Performance Data .............................................................................................. 3-11

3.2.9 Efficiency Data .............................................................................................................. 3-11

3.2.10 Shipments....................................................................................................................... 3-13

3.3 BOILER TECHNOLOGY ASSESSMENT .................................................................. 3-15

3.3.1 Boiler and Heat Exchanger Characterization................................................................. 3-15

3.3.2 Technology Options that may Improve AFUE.............................................................. 3-18

3.3.3 Technologies That Do Not Increase AFUE or Standby................................................. 3-22

3.3.4 Technology Options that Improve Standby Mode and Off Mode Energy Efficiency... 3-22

LIST OF TABLES

Table 3.2.1 Residential Boiler Manufacturers............................................................................. 3-5

Table 3.2.2 Current Federal Energy Conservation Standards Established by EISA ................... 3-8

Table 3.2.3 Canadian Energy Conservation Standards for Residential Boilers .......................... 3-8

Table 3.2.4 SEDBUK Efficiency Bands...................................................................................... 3-9

Table 3.2.5 ENERGY STAR Requirements for Qualifying Residential Boilers........................ 3-9

Table 3.2.6 CEE Efficiency Tiers for Residential Gas Boilers.................................................. 3-10

Table 3.2.7 Number of Boiler Models Listed in DOE’s Residential Boiler database by Product 

Class........................................................................................................................................... 3-11

Table 3.2.8 Historical shipments data of hot water and steam boilers reported from a SAIC report

.................................................................................................................................................... 3-14

Table 3.2.9 Appliance Magazine Shipments............................................................................. 3-14

LIST OF FIGURES

Figure 3.2.1 Replacement Distribution Channel.......................................................................... 3-7

Figure 3.2.2 New Construction Distribution Channel ................................................................. 3-7

Figure 3.2.3 AFUE Ratings for Residential Hot Water Boilers in the DOE Database.............. 3-12
3-ii

Figure 3.2.4 AFUE ratings for residential steam boilers in the DOE Database ........................ 3-13

Figure 3.2.5 Market Share of Shipments by Product Class (2003-2007).................................. 3-14

Figure 3.3.1 Gas-Fired Hot Water Boilers Heat Exchanger Materials in the DOE Database ... 3-17

Figure 3.3.2 Oil-fired Hot Water Boiler Heat Exchanger Materials in the DOE Database....... 3-18
3-1

CHAPTER 3.MARKET AND TECHNOLOGY ASSESSMENT

3.1 INTRODUCTION

This chapter provides a profile of the residential boiler industry in the United States. The 

U.S. Department of Energy (DOE) developed the initial market and technology assessment 

presented in this chapter primarily from publicly available information. This assessment is 

helpful in identifying the major manufacturers and characteristics of products on the market, 

which form the basis of the downstream analyses. 

This chapter consists of two sections: the market assessment and the technology 

assessment. The market assessment provides an overall picture of the market for the products

concerned, including a scope of the products covered, product classes, industry structure, 

manufacturer market shares; regulatory and non-regulatory efficiency improvement programs; 

and market trends and quantities of residential boilers sold. The technology assessment identifies 

an initial list of technology options for improving residential boiler efficiency to consider in the 

screening and engineering analyses. 

The information DOE gathers for the market and technology assessment serves as 

resource material for use throughout the rulemaking. DOE considers both quantitative and 

qualitative information from publicly available sources and interested parties.

3.1.1 Product Definitions and Scope of Coverage

Residential boilers are heating devices that transfer heat from combustion gases to water

or from electricity to water, which then provide heat to a home through a hot water or steam 

distribution system. 

Residential boilers are defined in the Energy Policy and Conservation Act (EPCA) as a 

type of furnace. Specifically, the term “furnace” is defined as: “a product which utilizes only 

single-phase electric current or direct current in conjunction with natural gas, propane, or home 

heating oil, and which –

(A) is designed to be the principal heating source for the living space of a residence;

(B) is not contained within the same cabinet with a central air conditioner whose rated 

cooling capacity is above 65,000 Btu [British thermal units] per hour;

(C) is an electric central furnace, electric boiler, forced- air central furnace, gravity 

central furnace, or low pressure steam or hot water boiler; and

(D) has a heat input rate of less than 300,000 Btu per hour for electric boilers and low 

pressure steam or hot water boilers and less than 225,000 Btu per hour for forced-air 

central furnaces, gravity central furnaces, and electric central furnaces.”

(42 U.S.C. 6291(23))
3-2

DOE has incorporated this definition into its regulations at 10 Code of Federal 

Regulations (CFR) 430.2. In addition, DOE has defined “electric boiler” and “low pressure 

steam or hot water boiler” at 10 CFR 430.2 as follows:

Electric boiler means an electrically powered furnace designed to supply low pressure 

steam or hot water for space heating application. A low pressure steam boiler operates at 

or below 15 pounds per square inch gauge (psig) steam pressure; a hot water boiler 

operates at or below 160 psig water pressure and 250 °F water temperature.

Low pressure steam or hot water boiler means an electric, gas or oil burning furnace 

designed to supply low pressure steam or hot water for space heating application. A low 

pressure steam boiler operates at or below 15 pounds psig steam pressure; a hot water 

boiler operates at or below 160 psig water pressure and 250 °F water temperature.

Appendix N to Subpart B of 10 CFR Part 430 references the definitions section of the 

American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) 103-

1993 (Method of Testing for Annual Fuel Utilization Efficiency of Residential Central Furnaces 

and Boilers), a which contains additional definitions of a boiler, many of which are similar to 

those listed above. Specifically, ASHRAE 103-1993 defines the following terms: 

Boiler: a self-contained fuel-burning or electrically heated appliance for supplying lowpressure steam or hot water for space-heating application.

Boiler, finned-tube: a boiler whose heat exchanger consists of only finned-tubes.

Boiler, low-pressure steam or hot water: an electric, gas, or oil-burning boiler designed to 

supply low-pressure steam or hot water for space-heating applications. A low-pressure 

steam boiler operates at or below 15 psig steam pressure; a hot water boiler operates at or 

below 160 psig water pressure and 250°F water temperature.

DOE has maintained the scope of coverage as defined by its current regulations for the

analysis of amended annual fuel utilization efficiency (AFUE) standards, which includes six

product classes of boilers (steam gas boilers, hot water gas boilers, steam oil boilers, hot water

oil boilers, steam electric boilers, and hot water electric boilers). DOE did not consider setting

new AFUE standards for electric boilers or separate standards for combination appliances for the 

reasons explained below.

Combination appliances are used to provide both space heating and domestic hot water to 

a residence. These products are currently available on the market in various configurations. 

Manufacturers currently certify combination appliances by rating the efficiency of the unit when 

performing their primary function. DOE did not evaluate these products in this analysis because 

DOE’s existing test procedures are not capable of rating the space and water heating 

 a American Society of Heating Refrigerating and Air-Conditioning Engineers, American National Standards 

Institute (ANSI)/ASHRAE 103-1993: Method of Testing for Annual Fuel Utilization Efficiency of Residential 

Central Furnaces and Boilers (1993).
3-3

performance of combination appliances and DOE has not yet adopted a test procedure to 

determine the energy efficiency of combination appliances in more than one operational mode.

DOE has not included electric boilers in this analysis of amended AFUE standards. 

Electric boilers currently do not have an AFUE requirement under 10 CFR 430.32(e)(2)(ii). 

Electric boilers typically utilize electric resistance coils as their heating elements and the 

efficiency of these products already approaches 100 percent AFUE. Therefore, there are no 

options for increasing the rated AFUE of this product, and the impact of setting AFUE energy 

conservation standards for these products would be negligible. There are technologies that can 

potentially improve the efficiency of electric boilers (e.g., heat pump technology), but such 

technologies are not captured by the AFUE metric. EPCA designated AFUE as the energy 

efficiency descriptor for residential boilers. (42 U.S.C. 6291(20)) The AFUE metric, as measured 

by the DOE test method, assigns a value of 100 percent for electric boilers, and would not 

capture the impact of any technologies to improve efficiency. However, DOE does intend to 

consider standby mode and off mode standards for electric boilers as described in the paragraph 

immediately below.

This rulemaking will analyze energy conservation standards for energy consumption of 

boilers operating in standby mode and off mode. Section 310(3) of EISA 2007 amended EPCA 

to require that energy conservation standards published after July 1, 2010, address standby mode 

and off mode energy use (42 U.S.C. 6295(gg)(3)), if justified by the criteria for adoption of 

standards in section 325(o) of EPCA (42 U.S.C. 6295(o)). Many residential boilers do not 

operate continuously. The AFUE metric accounts for fossil fuel consumption in standby mode 

and off mode but does not take electricity consumption into account in these modes. DOE 

adopted a test method for determining standby mode and off mode energy consumption of 

residential boilers in a final rule published on October of 2010. 75 FR 64621. Accordingly, this 

rulemaking will consider the electrical consumption of boilers in standby mode and off mode, as 

required by EPCA. 

3.1.2 Test Procedure

The energy conservation standards for residential boilers are represented in terms of the 

AFUE as measured by the DOE test procedure. (42 U.S.C. 6295(F)(3)). The DOE test procedure 

for determining the AFUE of residential boilers is located at Appendix N to Subpart B of 10 

CFR Part 430 and references ASHRAE Standard 103-1993 (Method of Testing for Annual Fuel 

Utilization Efficiency of Residential Central Furnaces and Boilers). AFUE is an annualized fuel 

efficiency metric that fully accounts for fuel consumption in active, standby, and off modes.

To satisfy the requirements of EPCA as amended by EISA, as noted above DOE updated

its test procedure for furnaces and boilers to establish a method for measuring the electrical 

energy use in standby mode and off mode for residential boilers in a final rule published on 

October 20, 2010. 75 FR 64621. These test procedure amendments were primarily based on and 

incorporate by reference provisions of the International Electrotechnical Commission (IEC) 

Standard 62301 (Second Edition), ‘‘Household electrical appliances—Measurement of standby 

power.” 
3-4

On January 2013, DOE published a request for information (RFI) which initiated a 

rulemaking to consider modifying the residential furnace and boiler AFUE test method. 78 FR

675. Key proposed issues addressed in the RFI included whether to change of reference from 

ASHRAE 103-1993 to ASHRAE 103-2007, as well as room temperature and humidity 

adjustment calculations. EPCA, as amended by EISA 2007, requires that DOE must review test 

procedures for all covered products at least once every 7 years. (42 U.S.C 6293(b)(1)(A)) 

Accordingly, DOE must complete this test procedure rulemaking no later than December 19, 

2014 (i.e., 7 years after the enactment of EISA 2007), which is before the expected completion of 

this standards rulemaking. DOE must base the analysis of amended standards on the most recent 

version of its test procedures, and accordingly, DOE will use the amended test procedure in 

future rulemaking stages when considering product efficiencies, energy use, and efficiency 

improvements in its analyses.

3.2 MARKET ASSESSMENT

The following market assessment identifies manufacturer trade associations, domestic 

and international manufacturers of residential boilers, and regulatory and non-regulatory 

programs. The market assessment also describes the cost structure for the residential boiler

industry and summarizes relevant market performance data.

3.2.1 Trade Association

The Air-Conditioning, Heating, and Refrigeration Institute (AHRI) is a national trade 

association of manufacturers of residential, commercial and industrial appliances and equipment, 

including residential boilers. AHRI was established in January of 2008 when the AirConditioning and Refrigeration Institute (ARI) merged with the Gas appliance Manufacturers 

Association (GAMA). AHRI develops and publishes technical standards for residential and 

commercial air conditioning, heating, and refrigeration equipment using rating criteria and 

procedures for measuring and certifying product performance. AHRI maintains the Directory of 

Certified Product Performance that lists all products that have been certified for performance by 

AHRI. AHRI maintains a certified performance directory for residential boilers. DOE used the 

data in the AHRI certification directory for residential boilers in its market assessment.

3.2.2 Manufacturers and Market Share

DOE constructed a database of residential boilers based on its review of the AHRI 

directory of certified performance for residential boilers1

, manufacturers’ websites and product 

catalogs, the ENERGY STAR listing of qualified residential boilers2, the California Energy 

Commission (CEC) appliance efficiency database3

, and the DOE certification and compliance 

management system4 (CCMS) database to create a comprehensive database of residential boilers 

available on the market. DOE examined this database to identify residential boiler 

manufacturers. DOE does not have empirical data on the market shares of particular 

manufacturers of residential boilers. However, in Table 3.2.1, DOE divided manufacturers into 

“major” and “other” based on DOE research and discussions with manufacturers. “Major” 
3-5

manufacturers are estimated to have a market share of at least 15 percent, and the rest of the 

manufacturers are considered as “other”.

Table 3.2.1 Residential Boiler Manufacturers

Company Parent Name (if 

applicable)

Market

Lochinvar Corporation A.O. Smith Water 

Products Company

Other

Crown Boiler Company Burnham Major

Burnham Commercial

Burnham Hydronics (US 

Boiler Company, Inc) 

New York Boiler Company, 

Inc.

Argo ECR International Major

ECR International, LTD -

Olsen Division

Oneida Royal

Dunkirk Boilers

Pennco, Inc.

Utica Boilers, Inc.

Ultimate Engineering

Hydrotherm Division of 

Mestek

Mestek Other

Smith Cast Iron Boilers

Embassy Industries Inc

RBI Water Heater Division of 

Mestek, Inc.

Raypak, Inc. Paloma Industries Other

Weil-McLain SPX Corporation Major

Williamson-Thermoflo

Bosch Bosch Other

Buderus

Viessmann 

Viessmann 

Manufacturing 

Company

Other

LAARS Heating Systems Bradford White Other

Axeman-Anderson Axeman-Anderson Other

Boyertown Furnace Company Boyertown Furnace 

Company

Other

Columbia Boiler Company of 

Pottstown

Columbia Boiler 

Company

Other

Navien Kyung Dong Network 

Co, Ltd.

Other

EFM EFM Other
3-6

Thermo-Dynamics Boiler 

Company

Thermo-Dynamics 

Boiler Company

Other

Camus Hydronics Camus Hydronics Other

Energy Kinetics Energy Kinetics Other

NY Thermal (NTI) Dennison Holdings 

Ltd.

Other

Triangle Tube ACV International

NV

Other

SIME North America SIME Other

Heat Transfer Products, Inc Heat Transfer 

Products, Inc

Other

PB Heat LLC Peerless Boilers Other

Slant/Fin Corporation Slant/Fin Corporation Other

Thermolec Thermolec Other

Allied Engineering Company E-Z-Rect 

Manufacturing Ltd.

Other

Pensotti Pensotti Other

3.2.3 Potential Small Business Impacts

DOE also takes into consideration the impact of amended energy conservation standards 

on small businesses. SBA lists small business size standards for industries as they are described 

in North American Industry Classification System (NAICS). For residential boilers, the size 

standard is matched to NAICS code 333414, Heating Equipment (except Warm Air Furnaces) 

Manufacturing. The number of employees in a small business is combined with the total 

employees of the parent company; it does not represent the division manufacturing residential 

boilers. At this time, DOE has identified 7 small businesses in the residential boiler market that 

fall under the Small Business Administration (SBA)’s definition as having 500 employees or 

fewer. 13 CFR part 121. DOE studies the potential impacts on these small businesses in detail 

during the Manufacturer Impact Analysis in the NOPR phase.

DOE has identified the following small business manufacturers of residential boilers:

• Axeman Anderson

• Thermo-Dynamics Boiler Company

• Energy Kinetics

• ECR International

• Heat Transfer Products, Inc.

• Peerless Boiler

• Slant/Fin Boiler

3.2.4 Distribution Channels
3-7

Two distribution channels represent the majority of the HVAC market. In the 

replacement market the original equipment manufacturer (OEM) assembles the system and sells 

it to a wholesaler; the wholesaler sells the unit to a contractor (also known as a dealer); and the 

contractor sells the unit to the final consumer and performs the installation. In the replacement 

market, the final consumer is usually the homeowner, as illustrated in Figure 3.2.1, and is very 

influential in product selection. Replacements "in kind" (replacing a unit with a similar or 

identical product) are common, although premium products are also commonly sold in this 

market. In the new construction distribution channel, the manufacturer sells to the equipment 

wholesaler, who in turn sells to the mechanical contractor, who in turn sells it to the general 

contractor then to the consumer. 

Figure 3.2.1 Replacement Distribution Channel

Figure 3.2.2 New Construction Distribution Channel

3.2.5 Regulatory Programs

The following section details current regulatory programs mandating energy conservation 

standards for residential boilers. Section 3.2.5.1 discusses current Federal energy conservation 

standards. Section 3.2.5.2 reviews Canadian energy conservation standards that may impact the 

companies servicing the North American market.

3.2.5.1 Current Federal Energy Conservation Standards

Part A of Title III of EPCA addresses the energy conservation standards for consumer 

products other than automobiles, which include residential boilers. (42 U.S.C. 6291-6309) The 

current Federal standards prescribed by EPCA, shown in Table 3.2.2, have applied since September, 

1, 2012.

Manufacturer Wholesaler Mechanical 

Contractor Consumer

Manufacturer Wholesaler Mechanical 

Contractor

General 

Contractor Consumer
3-8

Table 3.2.2 Current Federal Energy Conservation Standards Established by EISA

Product Class Minimum Annual Fuel 

Utilization Efficiency

Design Requirements

Gas Hot Water 82% No Constant Burning Pilot, 

Automatic Means for Adjusting 

Water Temperature

Gas Steam 80% No Constant Burning Pilot

Oil Hot Water 84% Automatic Means for Adjusting 

Temperature

Oil Steam 82% None

Electric Hot Water None Automatic Means for Adjusting 

Temperature

Electric Steam None None

3.2.5.2 Canadian Energy Conservation Standards

The Natural Resources Canada (NRCan) Office of Energy Efficiency regulation 

mandates minimum energy conservation standards for residential boilers that apply to imports 

and interprovincial trade. The standards for boilers are expressed as minimum annual fuel 

utilization energies (AFUEs), rated according to the Canadian test standard CAN/CSA P.2-2007 

entitled Testing method for measuring annual fuel utilization efficiency of residential gas-fired 

furnaces and boilers; (CSA P.2). The Canadian boiler standards are shown in Table 3.2.3. The 

AFUE standard became effective in September 1, 2010 and the prescriptive requirements became 

effective on September 1, 20125

.

Table 3.2.3 Canadian Energy Conservation Standards for Residential Boilers

Boiler Type Minimum AFUE Prescriptive Requirements

Gas Hot Water 82% No constant burning pilot; 

Automatic means for adjusting 

water temperature

Gas Steam 80% No constant burning pilot

Oil Hot Water 84% Automatic means for adjusting 

water temperature

Oil Steam 82% None

Electric Hot Water None Automatic means for adjusting 

water temperature

3.2.5.3 United Kingdom Energy Conservation Standards

Part L1 of the Building Regulations code in the United Kingdom requires that all gasfired boilers installed in England or Wales after April 1, 2005, and all oil fired boilers installed 

after April 1, 2007 must be a condensing boiler. These boilers must be rated A or B on the 

Seasonal Efficiency of Domestic Boilers in the UK (SEDBUK) scale6

. 
3-9

Table 3.2.4 SEDBUK Efficiency Bands

Efficiency Band SEDBUK

A 90% and above

B 86%-90%

C 82%-96%

D 78%-82%

E 74%-78%

F 70%-74%

G Below 70%

3.2.6 Non-Regulatory Programs

DOE identified non-regulatory programs aimed at improving the energy efficiency of 

residential boilers. Two such programs are based on voluntary efficiency targets for residential

boilers: the ENERGY STAR program and the Consortium for Energy Efficiency (CEE) 

initiative. 

3.2.6.1 ENERGY STAR

ENERGY STAR is a voluntary labeling program conducted by the U.S. Environmental 

Protection Agency (EPA) and DOE that identifies and promotes energy-efficient products. To 

qualify, a product must usually exceed Federal minimum standards by a specified amount, or if 

no Federal standard exists, it must meet minimum efficiency levels set by the program and/or 

exhibit selected energy saving features. ENERGY STAR maintains minimum energy efficiency 

specifications for various products, including residential boilers. The current ENERGY STAR 

levels are shown in Table 3.2.5 which took effect in April 1, 2002. EPA is currently in the 

process of reviewing the ENERGY STAR efficiency level for residential boilers.

Table 3.2.5 ENERGY STAR Requirements for Qualifying Residential Boilers

Product AFUE Rating

Residential Boiler 85

3.2.6.2 Consortium for Energy Efficiency

The Consortium for Energy Efficiency (CEE) is a coalition of energy efficiency programs 

in the U.S. and Canada, including state energy efficiency offices, energy efficiency advocacy 

groups, and utilities, engaged in establishing common goals and methods for promoting energy 

efficiency across a broad range of products. The CEE High Efficiency Residential Gas Heating 

Initiative promotes the use of high-efficiency gas residential boilers. CEE identifies two tiers of 

efficiency levels for residential boilers listed in Table 3.2.67.
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Table 3.2.6 CEE Efficiency Tiers for Residential Gas Boilers 

Tier AFUE Rating

Tier 1 85

Tier 2 90

3.2.6.3 Consumer Rebate Program

In addition to the Federal and State tax credits available for purchasers of residential 

boilers, many States and local utility companies offer rebates for higher efficiency boilers, 

typically for existing homes and retrofits only. DOE maintains a database for such rebates, called 

the Database of State Incentives for Renewables & Efficiency (DSIRE)8, in addition to 

information on other state, local, utility, and federal incentives and policies that promote 

renewable energy and energy efficiency. For more information on individual rebate programs, 

please visit the DSIRE website at www.dsireusa.org

3.2.6.4 Federal Tax Credits

Until December 31, 2010, a Federal tax credit provides consumers with a $150 credit 

towards their Federal income tax if they purchase qualifying residential boilers. To qualify for 

the Federal tax credit a hot water boiler should have an AFUE of 95 or greater9

. 

3.2.7 Product Lifetime

The lifetime of residential boilers can vary significantly depending on how often the 

system is used (which is dependent upon the climate of the region where the product is installed 

and the personal preferences of the consumer) and how regularly it is maintained and serviced. 

DOE reviewed available literature to determine the appropriate lifetime for residential 

boilers. Generally, most sources estimate the lifetimes of residential boilers to be in the 15 to 25 

year range. Appliance Magazine publishes an Annual Portrait of the U.S. Appliance Industry in 

which it estimates low, high, and average lifetimes for a range of home appliances, including 

gas-fired boilers, based on input from appliance experts and many additional sources. Appliance 

Magazine estimates the typical service lifetime range of a gas boiler is from 17 to 24 years.

10

DOE’s methodology for determining the lifetime of the products under analysis are 

described in detail in appendix 8-F. Using a combination or RECS data and shipment history, 

DOE estimated that the median lifetime for all residential boilers is 22 years. 

 

DOE interviewed several manufactures to gather information regarding the lifetime of 

residential boilers. Many manufacturers stated that the design and efficiency level of the boiler 

impacted its expected lifetime. During manufacturer interviews conducted for the initial 

analysis, several manufacturers stated that higher efficiency condensing boilers, made of 

stainless steel or cast aluminum often have shorter lifetimes than lower efficiency cast iron 

boilers. Manufacturers pointed to the warranties offered on both types of heat exchangers to 

substantiate their claims. However, these manufacturers also generally noted that condensing 
3-11

residential boilers have only been available a relatively short time, so estimating the lifetime is 

difficult. 

3.2.8 Market Performance Data

As explained previously, DOE examined several sources to compile a comprehensive 

database of residential boilers available on the market today. This database contains information 

such as manufacturer name, model number, input capacity, efficiency, and other physical and 

performance characteristics. DOE only examined products that meet EPCA’s definition of a 

residential boiler (see section 3.1 in this chapter). Table 3.2.7 shows the number of the models in 

the DOE database for each product class. As Table 3.2.7 indicates, the majority of residential 

boilers on the market are gas-fired hot water boilers.

Table 3.2.7 Number of Boiler Models Listed in DOE’s Residential Boiler database by 

Product Class

Product Class Number of Models as of September 2013

Gas-Steam 83

Gas-Hot Water 653

Oil-Steam 93

Oil-Hot Water 501

3.2.9 Efficiency Data

DOE characterized the distribution of boiler efficiencies currently available to consumers 

by separating the active models listed in the DOE database into their respective product classes

(section 3.1) and placing the models into bins based on their efficiency. The efficiency ratings

were rounded to the nearest whole percentage as specified in 10 CFR 430.23(n)(2) and separated 

into bins in sizes of 1 percent AFUE (i.e., 83.7 is in the 84 AFUE bin). DOE then counted the 

number of models in each efficiency bin to examine the distribution of product efficiency. 
3-12

Figure 3.2.3 AFUE Ratings for Residential Hot Water Boilers in the DOE Database

As shown in Figure 3.2.3, hot water boiler models generally fall into one of two ranges –

non-condensing (i.e., 82 to 86 percent AFUE) or condensing (i.e., at or above 90 percent AFUE). 

The efficiency distribution of the boilers varies based upon the fuel type used. This is because of 

the chemical makeup of the fuel combustion byproducts. Gaseous fuels such as natural gas and 

propane have a higher hydrogen content which causes more water vapor to be formed during 

combustion. This results in lower efficiencies in non-condensing gas boilers. Most noncondensing boilers are concentrated at 82 percent AFUE for gas fired hot water boilers and 85

percent AFUE for oil fired hot water boilers. Most condensing boilers are at either 90 or 95

percent AFUEb for gas-fired hot water boilers.

The majority of oil boilers on the market are non-condensing (i.e., less than 90 percent 

AFUE), however there are a small number of oil-fired condensing boiler models and most are at 

90 and 91 percent AFUE. Condensing oil boilers are less common due in part to the high sulfur 

content of heating oil which can cause additional maintenance and corrosion issues. New limits 

on maximum sulfur content of heating oil in the Northeast may reduce these issues. Using lowsulfur heating oil with boiler systems can not only reduce the emission of particulate matter, but 

also allow for the use of a secondary condensing heat exchanger. 

 b The high number of 90% AFUE ratings may be due in part to a recent rerating initiative for AHRI member 

manufacturers to address inflated ratings caused by an error in the DOE test procedure which impacted condensing 

boilers with two stage or modulating input rates. AHRI has lowered the stated AFUE ratings of certain boilers to 

90% for its member companies until a revised rating has been determined with the corrected test procedure. 

0

20

40

60

80

100

120

140

160

82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

Number of Models

AFUE, %

Oil

Gas
3-13

Figure 3.2.4 AFUE ratings for residential steam boilers in the DOE Database

As shown in Figure 3.2.4 residential steam boilers have efficiencies ranging from 80 

percent AFUE up to 86 percent AFUE. As with hot water boilers, the efficiency of the boilers 

varies based upon the fuel type used. There are no higher level efficiencies in steam boilers.

3.2.10 Shipments

To prepare an estimate of the national impact of energy conservation standards for 

residential boilers, DOE needed to estimate annual residential boiler shipments. For this stage of 

the rulemaking, DOE used data from Appliance Magazine, AHRI, and ENERGYSTAR to 

establish historical shipments by product class. DOE used shipment projections to calculate the 

national impacts of standards and to calculate the future cash flows of manufacturers. DOE 

developed shipments projections based on an analysis of key market drivers for a particular 

product (see chapter 9). 

DOE used this data for two main purposes. First, the shipment data and market trend 

information contributed to the shipments analysis and base-case forecast for residential boilers

(chapter 9). Second, DOE used the data to develop the installed stock of equipment for the 

national impact analysis (chapter 10). Although more detailed shipments data are given in 

chapter 9 and appendix 09-B, the shipments shown in this chapter illustrate the level of shipments

from 1990 to 2008.

Table 3.2.8 shows the shipment data collected from a SAIC report10 which includes 

shipments of boilers less than 250,000 btu/hr sold in the United States from 2003 to 2007.

0

5

10

15

20

25

30

35

40

45

80 81 82 83 84 85 86

Number of Models

AFUE, %

Oil

Gas
3-14

Table 3.2.8 Historical shipments data of hot water and steam boilers reported from a SAIC

report

Units Sold

Year 2003 2004 2005 2006 2007

Gas-Fired Steam 38,105 36,846 37,127 30,243 33,932

Gas-Fired Hot Water 186,627 189,417 179,717 155,499 147,873

Oil-Fired Steam 17,706 19,460 17,256 16,016 15,494

Oil Fired Hot Water 120,764 133,288 121,678 99,801 93,642

Figure 3.2.5 Market Share of Shipments by Product Class (2003-2007)

Appliance Magazine11,12 provides an estimate of annual unit shipments for various 

appliances, including residential boiler shipments. Table 3.2.9 shows the shipment data collected 

from Appliance Magazine up until 2008.

Table 3.2.9 Appliance Magazine Shipments

Year Gas Boiler Oil Boiler

1990 195,959 132,779

1991 176,814 119,420

1992 176,483 145,459

1993 195,751 151,783

1994 215,887 170,734

1995 187,601 150,402

1996 198,247 161,363

1997 205,717 159,767

1998 185,032 148,178

11%

5% 51%

33%

Gas-Fired Steam

Gas-Fired Hot Water

Oil-Fired Steam

Oil Fired Hot Water
3-15

1999 200,893 149,050

2000 224,317 144,124

2001 221,198 149,457

2002 213,936 147,919

2003 235,226 166,821

2004 236,964 162,468

2005 224,185 145,551

2006 195,827 121,054

2007 201,000 123,320

2008 192,332 121,539

3.3 BOILER TECHNOLOGY ASSESSMENT

The technology assessment focuses on understanding how residential boilers use energy 

and on identifying potential technology changes that would improve the efficiency of these 

products. Measures that improve the rated product efficiency are analyzed as “technology 

options.” The technologies identified in this assessment are based on existing technologies as 

well as working prototypes. In consultation with interested parties, DOE has created a list of 

technology options for consideration in this rulemaking. Following research into this list of 

technology options, those technology options that pass the screening criteria are considered 

suitable options for improving the efficiency of the product in the engineering analysis, and will 

assist DOE in determining the max-tech design as well as the cost of improving product 

efficiency.

At this time, DOE is aware of a set of technology options (discussed in further detail 

below) that could be used to improve residential boiler efficiency. The list of technologies below 

is focused on measures that would improve either the rated AFUE or reduce standby and/or off 

mode electrical energy consumption. DOE is aware of technologies that improve overall 

efficiency of residential boilers but do not improve AFUE or reduce standby/off mode energy 

consumption as measured by the DOE test procedure, and these technologies are described in 

section 3.3.3.

3.3.1 Boiler and Heat Exchanger Characterization

Fuel burning boilers transfer heat from the combustion gases to water, which is then sent 

to the heated space through a steam or hot water distribution system. The technology that is used 

for steam boilers is generally the same as that used for hot water boilers except that circulating 

pumps are not required in steam boilers. 

Residential boilers can be characterized by the type of heat exchanger material: cast-iron, 

steel, stainless steel, copper, and aluminum. The heat exchanger’s function is to transfer heat 

from the combustion gases to the heating medium (i.e. hot water or steam), which is then 
3-16

distributed to the heated space. There are various types of heat exchangers commonly used in 

residential boilers. 

Most noncondensing boilers are made with cast iron, copper, or steel heat exchangers. 

The most common heat exchanger design used in residential hot water and steam boilers is the 

cast-iron sectional boiler. In this design, water is heated in cast-iron chambers called sections. 

The sections are fit together to form an assembly, which is typically assembled horizontally. Hot 

combustion gases form in the combustion chamber near the bottom of the boiler and rise through 

cavities between the sections, transferring heat to the water within. Generally, the greater the 

number of sections, the greater the rate of heat output from the boiler.

There are two major categories of cast-iron boiler: dry-base and wet-base. A dry-base 

boiler is commonly used in atmospheric gas-fired boilers. In a dry-base boiler, the combustion 

chamber is under the fluid-backed sections. Combustion occurs on the surface of burner tubes 

suspended below the water-filled sections. Hot exhaust gases are drawn upward between boiler 

sections, or through fire tubes, and enter a flue gas collector at the top of the boiler. A wet-base 

boiler is a common configuration for oil-fired boilers. In a wet-base boiler, the top and sides of 

the combustion chamber are enclosed by fluid-backed sections. It has the advantage of exposing 

more of the section's surface area to the combustion chamber, which is completely surrounded by 

the water-filled heat exchanger13. 

The amount of metal in cast-iron boilers makes them relatively heavy. These boilers can

contain up to 15 gallons of water. The combination of metal- and water-weight enables them to 

absorb a significant amount of heat into their own material. This high thermal mass is

undesirable in situations where the boiler is significantly oversized, and thus experiences 

extended periods of off-time between firing cycles. During this time, residual heat remaining in 

the boiler's metal and water following burner shutdown can be carried up to the flue by air 

currents passing through the combustion chamber. The majority of gas-fired boilers have flue 

dampers to reduce the draft heat loss. The residual heat is also transferred through the boiler's 

jacket to the air surrounding the boiler.

Another commonly used heat exchanger design in non-condensing gas-fired residential 

hot water boilers is the copper water tube boiler. In copper water-tube boilers, the tubes are 

directly exposed to the combustion gases. Design variations include both vertical and horizontaltube arrangements. The tubes are usually manufactured with fins that increase the heat transfer 

area exposed to the flue gases. The high thermal conductivity of copper, relative to cast iron or 

steel, means that significantly less surface area is needed to achieve the same rate of heat 

transfer. This makes for smaller and significantly lighter boilers. Copper water-tube boilers 

require constant water circulation while being fired to prevent damage from thermal stress. This 

requirement must be incorporated into the design of system piping and control. 

The third material commonly used in non-condensing boilers is steel. In a steel fire-tube 

boiler, water surrounds a group of steel tubes through which the hot combustion gases pass. 

Spiral baffles known as turbulators are inserted into the fire tubes to increase heat transfer by 

inducing turbulence and slowing the passage of the exhaust gases. The fire tubes are welded to 

steel bulkheads at each end to form the overall heat-exchanger assembly.
3-17

Most steel boilers are built around horizontal fire-tubes. Some boilers route the flue gases 

through multiple tubes before they reach the flue-pipe connection. This allows additional heat to 

be extracted from the flue gases. 

Condensing boilers are typically made corrosion resistant metals such as stainless steel or 

aluminum as other metals will corrode due to the acidic condensate. Condensing boilers have a 

variety of different heat exchanger designs. Design variations include fire-tube, water tube, or 

sectional primary heat exchanger with a secondary condensing heat exchanger. The majority of 

condensing boilers are gas-fired. Condensing boilers are typically forced or induced draft 

because they cannot use a natural draft venting system, since the buoyancy of the cooler flue 

gases is not sufficient to draw the gases up the vent system. Condensing boilers are generally 

sold with more sophisticated controls than non-condensing boilers. 

Figure 3.3.1 Gas-Fired Hot Water Boilers Heat Exchanger Materials in the DOE Database

Figure 3.3.1 shows the breakdown of heat exchanger materials for gas-fired hot water 

boilers in the DOE database. In the non-condensing range (i.e., 82 to 88 percent AFUE) the 

majority of the boilers heat exchangers are made of cast-iron, a smaller number of models are 

comprised of copper and a small number are made of steel. The heat exchanger of a baseline unit 

is typically constructed from cast iron. In the condensing range (i.e., at or above 90 percent 

AFUE) the majority of heat exchangers are stainless steel with a smaller number of models made 

of aluminum. There are also a few condensing boilers made of cast iron some of which have an 

additional stainless steel heat exchanger. 

0

10

20

30

40

50

60

70

80

82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

Number of Models

AFUE, %

Steel

Cast Iron

Copper

Stainless Steel

Aluminum
3-18

Figure 3.3.2 Oil-fired Hot Water Boiler Heat Exchanger Materials in the DOE Database.

Figure 3.3.2 shows the breakdown of heat exchanger materials for oil-fired hot water 

boilers. In the non-condensing range the heat exchangers are mostly made of cast iron, a smaller 

number are made of steel. 

3.3.2 Technology Options that may Improve AFUE

DOE has identified the following technology options which have the potential to improve 

the efficiency of residential boilers.

1. Heat Exchanger Improvements

2. Modulating Operation

3. Dampers

4. Direct Vent

5. Pulse Combustion

6. Premix Burners

7. Burner Derating

8. Low Pressure Air Atomized Oil Burner

9. Delayed Action Oil Pump Solenoid Valve

10. Electronic Ignition

0

20

40

60

80

100

120

82 83 84 85 86 87 88 89 90 91

Number of Models

AFUE, %

Steel

Cast Iron
3-19

3.3.2.1 Heat Exchanger Improvements

Improving the heat exchanger for boilers increases the rate of transfer from the hot 

combustion gases to the heating medium (i.e. hot water or steam), which is then distributed to the 

heated space. The improved heat transfer increases the thermal efficiency and AFUE.

Improvements to the heat exchanger can be achieved by modifying baseline designs of 

standard boilers to (1) increase heat exchanger surface area, (2) modify or add heat exchanger 

surface features, (3) modify or add heat exchanger baffles and turbulators, and (4) increase the 

corrosion resistance of the heat exchanger to withstand flue gas condensation.

Increase Heat Exchanger Surface Area and addition of Mechanical Draft. The 

performance of the heat exchanger can be improved by increasing the surface area relative to the 

fuel input. An increase in surface area provides a larger surface over which heat transfer can 

occur. This increases the overall rate of heat transfer occurring in the boiler, thereby improving 

the boiler’s ability to efficiently extract heat from the hot combustion gases. The result is an 

increase in steady-state efficiency of the unit, and thus, the AFUE.

Mechanical draft systems can be added to boilers to enable the use of more efficient heat 

exchangers. Mechanical draft systems allow for increased heat exchange surface area and/or 

tighter flueways by overcoming the drop in pressure associated with restrictive flow passages in 

more efficient heat exchangers and by supplementing the loss of buoyancy in cooler flue gases to 

provide sufficient airflow. Mechanical draft systems can be designed as either induced draft or 

forced draft systems. An induced draft fan is located downstream of the heat exchanger and 

pulls flue gases through the gas pathway, creating negative pressure in the heat exchanger. A 

forced draft fan is located upstream of the heat exchanger and creates positive pressure in the 

heat exchanger that pushes the products of combustion through the system. 

Modify or add Heat Exchange Surface Features. An alternative to increasing the size 

of the heat exchanger is enhancing the effectiveness of the heat exchanger surfaces. One way this 

may be done is by adding surface features to the heat exchanger. Incorporating surface features, 

such as dimples, increases the turbulence in the air passing close to the heat exchanger’s surface, 

which can enhance heat transfer when correctly designed.

Heat Exchanger Baffles and Turbulators. Turbulators and baffles are pieces of metal 

that are incorporated into the heat exchanger to improve the heat transfer through the walls of the 

heat exchanger. 

Increasing the Corrosion Resistance of the Heat Exchanger. When efficiency of a 

combustion heating appliance is increased to the point where combustion gases are cooled below 

the dew point of the gas, condensate will form. Flue gas condensate is acidic and corrosive. 

Corrosion due to condensation of flue gases limits the AFUE that can be achieved by boilers 

with non-corrosion resistant heat exchangers. Using heat exchangers made out of corrosion 

resistant materials, such as cast aluminum and stainless steel, allows for the recovery of the latent 

heat (the heat from condensation of water vapor in the combustion products) and raises the 

AFUE to above 90 percent. These types of boilers require the addition of a condensate pump and 

mechanical draft system.
3-20

3.3.2.2 Modulating Operation

Two-stage and modulating combustion allows boilers to meet heating load requirements 

more precisely. When low heating load conditions exist, a two-stage or modulating boiler can 

operate at a reduced input rate for an extended period of burner on-time to meet the reduced 

heating load. When combustion air supply is also modulated to match the fuel input rate, the 

burner is essentially derated, making the heat exchanger more effective in periods of lower heat 

demand, raising the AFUE. 

The primary difference between two-stage and step-modulating control is that the twostage control must operate between either the low firing rate and off, or the high firing rate and 

off, whereas the continuous modulating control can operate between multiple firing rates (e.g., 

off to low-fire to high-fire to low-fire to off). 

3.3.2.3 Dampers

Off-cycle (which refers to the burner off-cycle) dampers restrict the intake and exhaust 

air flow through the venting system during standby mode by closing when the burner is not 

operating, thereby trapping residual heat in the heat exchanger. During the burner off-cycle, the 

boiler loses heat by natural convection and conduction through the combustion air inlet and flue. 

Installing a damper at these points improves AFUE by preventing heat from escaping and 

minimizing off-cycle heat losses. Today most atmospheric boilers have dampers, including 

those at the baseline efficiency level.

3.3.2.4 Direct Vent

Direct-vent appliances use ducts to provide outdoor air for combustion. Non-direct-vent 

appliances typically use air from the appliance's environment for combustion. Direct-vent 

systems may use a combustion-air preheat system that passes the outdoor combustion air through 

a heat exchanger in contact with the flue gases. The combustion air does not mix with the flue 

gases. The so-called direct-vent with preheat design uses a concentric vent/combustion air 

system in which the flue gases pass through a central-vent pipe and the combustion air passes 

through a concentric duct surrounding it. This arrangement creates a counter-flow heat 

exchanger that recovers some heat from the flue gases to preheat the combustion air.

The direct-vent-without-preheat design is the same as the direct-vent-with-preheat design, 

except that the combustion air is not preheated by the flue gases. There are separate vent and 

combustion air systems and the combustion air is not preheated. The current test procedure does 

not differentiate between the performances of direct-vent with and without preheat technology; 

both are evaluated as isolated combustion system (ICS) installations. Direct vent boilers 

improves AFUE by reducing the heat loss through infiltration.

3.3.2.5 Pulse Combustion

Pulse combustion burners operate on self-sustaining resonating pressure waves that 

alternately rarefy the combustion chamber (drawing a fresh fuel-air mixture into the chamber) 

and pressurize it (causing ignition by compression heating of the mixture to its flash point). Pulse 

combustion systems feature high heat transfer rates, and have a high combustion efficiency in 

comparison to conventional boiler designs. DOE notes that similar efficiencies can be achieved 
3-21

through the use of other technologies, and manufacturers currently typically no longer use this 

technology to improve efficiency.

3.3.2.6 Premix Burners

Premixing fuel gas and combustion air prior to arrival at the flame results in more 

complete combustion using lower levels of excess air. The lower levels of excess air raise the 

temperature of the gases entering the heat exchanger which enhances heat exchange and 

improves efficiency. Lower levels of excess air also raise the water vapor dew point which 

facilitates condensation and the recovery of latent heat and improves AFUE. Premix burners 

have lower NOX emissions than traditional burners. 

3.3.2.7 Burner Derating

Reducing burner firing rate for gas and oil boilers while keeping heat exchanger 

geometry and surface area and the fuel-air ratio the same will increase the ratio of heat transfer 

surface area to energy input, thereby increasing the AFUE. However, DOE notes that the lower 

energy input means that less heat would be provided than with conventional burner firing rates. 

3.3.2.8 Low-Pressure, Air-Atomized Oil Burner 

The residential oil burner market is currently dominated by the pressure-atomized 

retention head burner. The fuel input rate is controlled by the size of the nozzle orifice. Pressureatomizing nozzles that are designed for low firing rates suffer rapid fouling of the small internal 

passages, leading to bad spray patterns and poor combustion performance. To overcome the low 

input limitations of conventional oil burners, Brookhaven National Laboratory14 developed a 

low-pressure, air-atomized oil burner. In addition, it can operate with low levels of excess 

combustion air for lean-burning, ultra-clean combustion. A lower level of excess air generally 

improves AFUE rating.

3.3.2.9 Delayed-Action Oil Pump Solenoid Valve

A delayed-action oil pump solenoid valve is installed between the oil pump and the 

burner nozzle to supplement the fuel pump regulator. It does so by delaying the fuel release by 

three to six seconds after the igniter and burner blower start until the oil pressure reaches the 

level required to fully discharge the oil into the combustion chamber without dripping. This 

ensures that the oil burns more completely, which improves efficiency. 

3.3.2.10 Electronic Ignition

Boilers are equipped with electronic ignition systems, which light the burner with an 

electrical component upon a call for heat. Unlike standing pilot ignition systems that consume 

fuel continuously, electronic devices and their control modules operate only during the active 

mode this improves AFUE. Electronic ignition is already required for all gas boilers and is 

present on oil boilers. 

There are different types of electronic ignition systems including:

(1) Hot Surface Ignition: The igniter in this system is an electrically heated resistance 

element that thermally ignites the main burner directly without the use of a pilot light. 

(2) Intermittent Pilot Ignition: This is a device that lights a pilot light by generating a 

spark. The pilot light in turn lights the main burner. 

(3) Direct Spark Ignition: DSI ignites the main burner directly by generating a spark.
3-22

(4) Interrupted Duty Ignition Systems: all modern oil burners have a type of electronic 

ignition called interrupted duty ignition. A step-up transformer supplies power to two 

electrodes, which causes a spark to jump. The interrupted duty ignition system for an oil 

burner activates the spark only until either a steady flame is established or the end of a 

timed trail-for-ignition (TFI) period. 

3.3.3 Technologies That Do Not Increase AFUE or Standby

DOE has listed technologies that may improve overall efficiency of residential boilers but 

do not improve AFUE or reduce standby/off mode energy consumption. These technologies are 

described in detail in chapter 4. As discussed in chapter 4, these technologies were not 

considered beyond the screening analysis because they do not impact the rated efficiency.

• Micro Combined Heat and Power (Micro-CHP)

• Improved Motor Efficiency

• Positive Shut-Off Valve for Oil Burner Nozzles

• Heat Pump Boilers

3.3.4 Technology Options that Improve Standby Mode and Off Mode Energy Efficiency

On October 20, 2010 DOE published a final rule in the Federal Register in which it 

concluded that it is not technically feasible to create an integrated metric that incorporates 

standby mode and off mode energy consumption into the statutorily-identified efficiency 

descriptor, AFUE. The October 2010 final rule amended DOE’s test procedure for furnaces and 

boilers to establish a method for measuring the electrical energy use in standby and off mode for 

gas and oil-fired boilers pursuant to requirements established by EISA 2007. 75 FR 64621. The 

technologies described in this section would reduce the standby mode and off mode energy 

consumption as measured by the DOE test procedure.

3.3.4.1 Transformer Improvements

Transformers continue to supply power to the control board in all modes of operation, 

including standby mode. Increasing their operating efficiency will reduce the boiler’s standby 

electrical power consumption. 

A toroidal transformer has an annular core made of very tightly-wound, grain-oriented, 

silicon steel ribbons, which are arranged such that all their molecules are aligned with the 

direction of flux. This allows better performance (i.e., more quiet and efficient operation) than a 

traditional laminated transformer, in which unaligned molecules increase the core’s reluctance, 

or capacity for opposing magnetic induction. These improvements in efficiency allow an up to 

50 percent reduction in size and weight, such that they can be used in new, innovative 

applications. Overall efficiency of toroidal transformers is 90 to 95 percent15.

Research has shown that larger, low loss transformers (LLTX) use four times less energy 

in standby than do off-the shelf transformer16.
3-23

3.3.4.2 Control Relay for Models with Brushless Permanent Magnet (BPM) 

Motors 

During testing of standby and off mode components performed for the DOE furnace and 

central air conditioner rulemakingc, DOE found that BPM motors and their associated controls 

consume power while in standby and/or off modes, while PSC motors did not have any standby 

or off mode power draw. Therefore for those boilers that utilize them, the BPM motor and 

associated controls could be disconnected while the system is in standby mode or off mode 

through the use of a control relay to further reduce a system’s standby/off mode power 

consumption. A typical control relay activates a switch when current runs through it and when 

there is no current a spring holds the switch in the open position. 

3.3.4.3 Switching Mode Power Supply

While linear power supplies regulate voltage supply to the dc circuit with a series 

element, switching mode power supplies (SMPS) do so in an alternative, more effective way. In 

a switching mode power supply, power handling electronics switch on and off (where ‘on’ 

means the switch is closed and voltage drop is negligible and ‘off’ means the switch is open and 

current is negligible) with high frequency, effectively connecting and disconnecting the output 

(load) to the input source. Continuous power flow to the load can be maintained/controlled by 

varying the duty cycle or frequency of the SMPS. 

Linear power supplies experience significant heat losses because they use resistance 

elements, which convert electrical energy to heat energy, to regulate power supply. By using a 

switch to control energy flow instead, switching mode power supplies avoid such heat losses and 

have much higher efficiency. SMPS do introduce transient losses that increase with frequency, 

but these losses are negligible in comparison with the energy saved. Thus, replacing a linear 

power supply with an SMPS has the potential to reduce the electrical power consumption of 

residential boilers in standby and off mode. 

 c

See:http://www1.eere.energy.gov/buildings/appliance_standards/residential/residential_furnaces_cac_hp_final_rule

.html
3-24

REFERENCES

1 Air-Conditioning, Heating, and Refrigeration Institute (AHRI). AHRI Directory of 

Certified Product Performance.(Last accessed August, 2013.)

<http://www.ahridirectory.org/ahridirectory/pages/home.aspx>

2 ENERGYSTAR. ENERGYSTAR Certified Products Database. (Last accessed January, 

2013.)

< http://www.energystar.gov/productfinder/product/certified-boilers/results>

3 California Energy Commission (CEC). California Energy Commission Appliance 

Database. (Last accessed January, 2013.)

< http://www.appliances.energy.ca.gov/AdvancedSearch.aspx>

4 Department of Energy (DOE). Compliance Certification Database. (Last accessed 

January, 2013.)

< http://www.regulations.doe.gov/certification-data/>

5 National Resources Canada (NRCan). Residential Boilers. (Last accessed October, 2013.)

< http://oee.nrcan.gc.ca/energy-efficient-products/hvac/7025>

6 Haringey Council. Building Regulations. England and Wales. (Last accessed October, 

2013.)

< http://www.haringey.gov.uk/part-l1-guide.pdf >

7 Consortium for Energy Efficiency (CEE). CEE High Efficiency Residential Gas Heating 

Initiative .(Last accessed October, 2013.)

< http://library.cee1.org/content/cee-high-efficiency-residential-gas-heating-initiativedescription-2010 >

8 Database of State Incentives for Renewables & Efficiency (DSIRE). Last accessed 

October, 2013.)

< http://dsireusa.org/>

9 Database of State Incentives for Renewables & Efficiency (DSIRE). Residential Energy 

Efficiency Tax Credit. Last accessed October, 2013.)

< http://www.dsireusa.org/incentives/incentive.cfm?Incentive_Code=US43F>

10 Science Applications International Corporation, Development of Issues Papers for GHG 

Reduction Project Types: Boiler Efficiency Projects, Table 2, January 7, 2009. 
3-25

<http://www.climateactionreserve.org/wp-content/uploads/2009/03/future-protocoldevelopment_boiler-efficiency.pdf>

11 U.S. Appliance Industry Statistical Review. Appliance Magazine, 2000.

12 U.S. Appliance Industry Statistical Review. Appliance Magazine, 2009. 

13 ASHRAE 2008 HVAC Systems and Equipment Handbook (Available at: 

https://www.ashrae.org/resources--publications/handbook). 

14 Brookhaven National Laboratory. (2007) ‘Durability of Very Low Capacity Pressure 

Atomized Fuel Nozzles Used with Low Firing Rate Residential Oil Burners.

15 Tabtronics, Inc. Toroidal Transformers. (Last accessed September 12, 2013.) 

<http://www.raftabtronics.com/TECHNOLOGY/ElectromagneticBasics/ToroidalTransforme

rBasics/tabid/112/Default.aspx>.

16 N. Nielsen. “Loss Optimizing Low Power 50 Hz Transformers Intended for AC/DC Standby 

Power Supplies.” Applied Power Electronics Conference and Exposition, 2004. IEEE, pp. 

420–425, September 9, 2004.