3-i

CHAPTER 3. MARKET AND TECHNOLOGY ASSESSMENT

TABLE OF CONTENTS

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

3.1.1 Product Definitions................................................................................................ 3-1

3.1.2 Product Classes...................................................................................................... 3-4

3.1.3 Test Procedures ..................................................................................................... 3-6

3.2 MARKET ASSESSMENT............................................................................................... 3-7

3.2.1 Trade Associations................................................................................................ 3-7

3.2.2 Manufacturers and Market Share ........................................................................ 3-10

3.2.3 Distribution Channels.......................................................................................... 3-17

3.2.4 Regulatory Programs........................................................................................... 3-18

3.2.5 Non-Regulatory Programs................................................................................... 3-21

3.2.6 Industry Cost Structure........................................................................................ 3-26

3.2.7 Product Lifetime.................................................................................................. 3-28

3.2.8 Market Performance Data ................................................................................... 3-29

3.2.9 Historical Shipments and Efficiencies ................................................................ 3-46

3.2.10 Saturations in U.S. Households........................................................................... 3-52

3.3 FURNACE TECHNOLOGY ASSESSMENT............................................................... 3-53

3.3.1 Furnace Characterization..................................................................................... 3-53

3.3.2 Baseline Product Components and Operation..................................................... 3-56

3.3.3 Technology Options That Improve AFUE.......................................................... 3-59

3.3.4 Technologies Options That Do Not Improve AFUE........................................... 3-67

3.4 CENTRAL AIR CONDITIONER AND HEAT PUMP TECHNOLOGY ASSESSMENT

3-68

3.4.1 Compressor Improvements.................................................................................. 3-68

3.4.2 Fan System Improvements.................................................................................. 3-69

3.4.3 Expansion Valve Improvements ......................................................................... 3-70

3.4.4 Heat Exchanger Technologies and Improvements.............................................. 3-71

3.4.5 Inverter Technology ............................................................................................ 3-74

3.4.6 Designs Relevant Only to Heat Pumps ............................................................... 3-74

3.4.7 Solar Assisted Central Air Conditioners and Heat Pumps.................................. 3-77

3.5 STANDBY MODE AND OFF MODE TECHNOLOGY ASSESSMENT ................... 3-77

3.5.1 Design Options Applicable to All Products........................................................ 3-77

3.5.2 Standby Mode Design Options Applicable Only to Furnaces ............................ 3-78

3.5.3 Off Mode Design Options Applicable Only to Central Air Conditioners and Heat 

Pumps 3-79

LIST OF TABLES

Table 3.1.1 Product Classes for Residential Furnaces Used in this Rulemaking ........................ 3-5

Table 3.2.1 AHRI Directory of Certified Product Performance Classifications for Residential 

Central Air Conditioners and Heat Pumps................................................................................... 3-9

Table 3.2.2: Manufacturers Whose Products are Included in DOE's Database*....................... 3-11
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Table 3.2.3 Manufacturers of Residential Oil-Fired Furnaces .................................................. 3-13

Table 3.2.4 Manufacturer Brand Names Found in the AHRI’s Directories of Certified Product 

Performance for Residential Central Air Conditioners and Heat Pumps .................................. 3-14

Table 3.2.5 Current Federal Energy Conservation Standards Established by EPCA, as Amended 

by NAECA................................................................................................................................. 3-18

Table 3.2.6 Federal Energy Conservation Standards Established by the November 2007 Rule3-18

Table 3.2.7 Current Federal Energy Conservation Standards for Residential Central Air 

Conditioners and Heat Pumps.................................................................................................... 3-19

Table 3.2.8 Canadian Energy Conservation Standards for Residential Gas Furnaces .............. 3-20

Table 3.2.9 Canadian Energy Conservation Standards for Residential Central Air Conditioners 

and Heat Pumps ......................................................................................................................... 3-20

Table 3.2.10 ENERGY STAR Levels for Split System and Single Package Residential Central 

Air Conditioners and Heat Pumps............................................................................................. 3-22

Table 3.2.11 CEE Tiers for Residential Central Air Conditioners and Heat Pumps................. 3-22

Table 3.2.12 Federal Tax Credits for Residential Furnaces....................................................... 3-23

Table 3.2.13 Federal Tax Credits for Residential Central Air Conditioners and Heat Pumps.. 3-23

Table 3.2.14 State Tax Credits for Residential Gas Furnaces ................................................... 3-24

Table 3.2.15 Oregon Tax Credit for Central Air Conditioners.................................................. 3-25

Table 3.2.16 Oregon Tax Credits for Heat Pumps29 .................................................................. 3-25

Table 3.2.17 FEMP Performance Requirements for Residential Central Air Conditioners...... 3-26

Table 3.2.18 FEMP Performance Requirements for Air Source Heat Pumps........................... 3-26

Table 3.2.20 Air Conditioning and Warm Air Heating Equipment Industry Cost Data .......... 3-28

Table 3.2.21 Number of Furnace Models Listed in the AHRI Directory of Certified Product 

Performance by Product Class................................................................................................... 3-29

Table 3.2.22 Number of Central Air Conditioner and Heat Pump Models Listed in the AHRI 

Directory of Certified Product Performance by Product Class.................................................. 3-30

Table 3.2.23 Central Air Conditioner and Heat Pump Shipments............................................. 3-49

Table 3.2.24 Value of Residential Furnace Shipments by Year................................................ 3-50

Table 3.2.25 Value of Residential Central Air Conditioner and Heat Pump Shipments by Year. 3-

50

Table 3.2.26 Central Air Conditioner Shipment-Weighted Efficiency Growth Rates.............. 3-51

Table 3.2.27 Heat Pump Shipment-Weighted Efficiency Growth Rates................................... 3-52

Table 3.2.28 Central Air Conditioner Heat Pump Historical Housing Stock Saturations......... 3-53

LIST OF FIGURES

Figure 3.2.1 2008 Market Shares for U.S. Manufacturers of Residential Gas Furnaces........... 3-13

Figure 3.2.2 2008 Market Shares for Unitary Air Conditioners and Heat Pumps.................... 3-15

Figure 3.2.3 Traditional Distribution Chain in Replacement Market........................................ 3-17

Figure 3.2.4 Direct-to-Dealer Distribution Chain in Replacement Market ............................... 3-17

Figure 3.2.5 Distribution Chain in New Construction Market .................................................. 3-17

Figure 3.2.6 Distribution of Non-Weatherized Gas Furnace Models by AFUE ....................... 3-30

Figure 3.2.7 Distribution of Weatherized Gas Furnace Models by AFUE................................ 3-31

Figure 3.2.8 Distribution of Mobile Home Gas Furnace Models by AFUE.............................. 3-31

Figure 3.2.9 Distribution of Non-Weatherized Oil-Fired Furnace Models by AFUE............... 3-32
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Figure 3.2.10 SEER Ratings for Single Package Central Air Conditioners in the AHRI Certified 

Product Performance Directory ................................................................................................. 3-33

Figure 3.2.11 SEER Ratings for Single Package Heat Pumps in the AHRI Certified Product 

Performance Directory............................................................................................................... 3-33

Figure 3.2.12 SEER Ratings for Split System Central Air Conditioners in the AHRI Certified 

Product Performance Directory ................................................................................................. 3-34

Figure 3.2.13 SEER Ratings for Split System Heat Pumps in the AHRI Directory of Certified 

Product Performance.................................................................................................................. 3-34

Figure 3.2.14 SEER Ratings for SDHV Systems in the AHRI Directory of Certified Product 

Performance ............................................................................................................................... 3-35

Figure 3.2.15 HSPF Ratings for Single Package Heat Pumps in AHRI’s Directory of Certified 

Product Performance.................................................................................................................. 3-36

Figure 3.2.16 HSPF Ratings for Split System Heat Pumps in AHRI’s Directory of Certified 

Product Performance.................................................................................................................. 3-36

Figure 3.2.17 HSPF Ratings for SDHV Heat Pumps in AHRI’s Directory of Certified Product 

Performance ............................................................................................................................... 3-37

Figure 3.2.18 Distribution of Non-Weatherized Gas Furnace Models by Input Capacity ........ 3-38

Figure 3.2.19 Distribution of Weatherized Gas Furnace Models by Input Capacity ................ 3-38

Figure 3.2.20 Distribution of Mobile Home Gas Furnace Models by Input Capacity .............. 3-39

Figure 3.2.21 Distribution of Non-Weatherized Oil-Fired Furnace Models by Input Capacity3-39

Figure 3.2.22: Number of Models at Selected Cooling Capacities............................................ 3-40

Figure 3.2.23: Number of Models at Selected Cooling Capacities............................................ 3-40

Figure 3.2.24 Average SEER Ratings at Incremental Cooling Capacities for Single Package Air 

Conditioners in AHRI’s Directory of Certified Product Performance ...................................... 3-41

Figure 3.2.25 Average SEER Ratings at Incremental Cooling Capacities for Split System Air 

Conditioners in AHRI’s Directory of Certified Product Performance ...................................... 3-41

Figure 3.2.26 Average SEER Rating at Incremental Cooling Capacities for Single Package Heat 

Pumps in the AHRI Directory of Certified Product Performance ............................................. 3-42

Figure 3.2.27 Average SEER Rating at Incremental Cooling Capacities for Split System Heat 

Pumps in the AHRI Directory of Certified Product Performance ............................................. 3-42

Figure 3.2.28: Number of Models at Selected Cooling Capacities............................................ 3-43

Figure 3.2.29 Average HSPF at Incremental Cooling Capacities for Single Package Heat Pumps 

in the AHRI Directory of Certified Product Performance ......................................................... 3-43

Figure 3.2.30 Average HSPF Rating at Incremental Cooling Capacities for Split System Heat 

Pumps in the AHRI Directory of Certified Product Performance ............................................. 3-44

Figure 3.2.31 Average EER Ratings at Incremental Cooling Capacities for Single Package Air 

Conditioners in AHRI’s Directory of Certified Product Performance ...................................... 3-45

Figure 3.2.32 Average EER Ratings at Incremental Cooling Capacities for Split System Air 

Conditioners in AHRI’s Directory of Certified Product Performance ...................................... 3-45

Figure 3.2.33 Average EER Rating at Incremental Cooling Capacities for Single Package Heat 

Pumps in the AHRI Directory of Certified Product Performance ............................................. 3-46

Figure 3.2.34 Average EER Rating at Incremental Cooling Capacities for Split System Heat 

Pumps in the AHRI Directory of Certified Product Performance ............................................. 3-46

Figure 3.2.35 Residential Furnace Industry Shipments (Domestic and Imported).................... 3-47

Figure 3.2.36 Average Fuel Prices, 2000 to 2009,, .................................................................... 3-48
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Figure 3.2.37 Central Air Conditioner Historical Shipment-Weighted Efficiencies with Linear 

Fits.............................................................................................................................................. 3-51

Figure 3.2.38 Heat Pump Historical Shipment-Weighted Efficiencies base on SEER with Linear 

Fits.............................................................................................................................................. 3-52
3-1

CHAPTER 3. MARKET AND TECHNOLOGY ASSESSMENT

3.1 INTRODUCTION

This chapter details the market and technology assessment that the U.S. Department of 

Energy (DOE) has carried out in support of the ongoing energy conservation standards 

rulemaking for residential furnaces and residential central air conditioners and heat pumps. It 

consists of two sections: the market assessment and the technology assessment.

The goal of the market assessment is to develop a qualitative and quantitative 

characterization of both the residential furnace and the residential central air conditioner and heat 

pump industries and market structures, based on publicly available information and data and 

information submitted by manufacturers and other stakeholders. The technology assessment is a 

preliminary list of technologies that can improve the efficiency of residential furnaces and 

residential central air conditioners and heat pumps. These technologies are considered in the 

screening analysis

For furnaces, DOE examined publicly available information from the Air-Conditioning, 

Heating, and Refrigeration Institute (AHRI) Consumers' Directory of Certified Efficiency 

Ratings for Furnaces1

, the appliance efficiency database from the California Energy Commission 

(CEC)2

, the appliance database from ENERGY STAR3, and the Consortium for Energy 

Efficiency (CEE) Residential Natural Gas Furnaces Qualified Products List4

For central air conditioners and heat pumps, DOE examined the equipment certification 

directory from the Air-Conditioning, Heating and Refrigeration Institute (AHRI), as well as 

Current Industry Reports (CIR) and Annual Survey of Manufactures (ASM) from the U.S. 

Census Bureau. Issues addressed include: manufacturer characteristics and market shares; 

existing regulatory and non-regulatory efficiency improvement initiatives; product classes; and 

trends in the equipment markets and characteristics.

. DOE consolidated 

these databases, eliminating all duplicate and discontinued models, into a master list of furnaces 

on the market, which hereinafter will be referred to as DOE’s database. 

3.1.1 Product Definitions

3.1.1.1 Furnaces

A residential, or warm-air, furnace is an integral part of a home’s central heating and 

cooling system that provides heated air to the conditioned space through ductwork. A fuelburning furnace provides which by passing the combustion products through an air-to-air heat 

exchanger. The furnace uses a blower to propel circulation air over the outside of the heat 

exchanger, transferring heat from the hot combustion gases to the cool circulation air. The heated 

air is then distributed via ductwork to the conditioned space, and the products of combustion are 

exhausted from the heat exchanger to the atmosphere through the flue passage. 

The Energy Policy and Conservation Act (42 U.S.C. 6291 et seq.; EPCA) defines a 

residential “furnace” as a product that utilizes only single-phase electric current, or single-phase 
3-2

electric current or DC current in conjunction with natural gas, propane, or home heating oil, and 

which:

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

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

cooling capacity is above 65,000 Btu per hour;

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

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

(4) 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)) 

Although the definition in EPCA covers a number of different types of products, as 

discussed in the final rule, DOE maintained the scope of coverage from the November 2007 Rule

for its analysis of amended AFUE standards, which included four product classes of furnaces 

(non-weatherized gas furnaces, weatherized gas furnaces, mobile home gas furnaces, and nonweatherized oil-fired furnaces). DOE did not consider amended standards for mobile home oilfired furnaces and weatherized oil-fired furnaces because there are very few shipments of these 

products, such that the energy savings resulting from amended efficiency standards would be de 

minimis. DOE initially made this determination for the November 2007 Rule, and the markets for 

mobile home oil-fired furnaces and weatherized oil-fired furnaces have not changed. 71 FR 

59204, 59214 (Oct. 6, 2006). DOE considers the opportunity for energy savings to be 

insignificant for these product classes due to their extremely low shipment volumes. DOE also 

did not consider amended AFUE standards for electric furnaces. The efficiency of these products 

already approaches 100 percent AFUE, and thus, the impact of amending the AFUE energy 

conservation standards for these products would be de minimis. However, DOE did consider 

standby mode and off mode standards for electric furnaces as described below.

This rulemaking will establish energy conservation standards for energy consumption of 

furnaces operating in standby mode and off mode. Section 310(3) of the Energy Independence 

and Security Act of 2007 (EISA 2007; Pub. L. 110-140) 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)), if justified by the criteria for adoption of standards in section 325(o) of 

EPCA (42 U.S.C. 6295(o)). In this rulemaking, DOE intends to incorporate such energy use into 

any amended standard it adopts in the final rule, which is scheduled to be issued by June 30, 

2011.

DOE’s current standards for furnaces are expressed as minimum annual fuel utilization 

efficiencies (AFUE). AFUE is an annualized fuel efficiency metric that fully accounts for fuel 

consumption in active, standby, and off modes. DOE published a test procedure final rule in the 

Federal Register on October 20, 2010 (hereafter referred to as the October 2010 TP Rule), that 

amended DOE’s test procedure for furnaces and boilers to establish a method for measuring the 

electrical energy use in standby mode and off mode for gas and oil-fired furnaces. For this 

rulemaking, DOE is assuming that homeowners are unlikely to switch their furnaces to off mode 

in the non-heating season; and therefore the power consumed in off mode is equivalent to the 

power consumed in standby mode. As such, DOE is issuing separate but equivalent standards for 
3-3

maximum standby and off mode electrical energy consumption for all furnaces covered in this 

rulemaking.

3.1.1.2 Central Air Conditioners and Heat Pumps

A residential central air conditioner is another important part of a home’s central heating 

and cooling system that provides cooled air to the conditioned space through ductwork. The air 

conditioner uses a blower, which for split systems may be contained in the furnace, to propel 

circulation air over the outside of a heat exchanger (i.e. evaporator coil), transferring heat from 

warm circulation air to the cool refrigerant. The cooled air is then distributed via ductwork to the 

conditioned space, while a compressor is used to further raise the refrigerant temperature before 

the refrigerant transfers heat to the atmosphere through another heat exchanger (i.e. condenser 

coil). Split system air conditioners are comprised of an indoor unit, which contains the 

evaporator coil and indoor blower, and an outdoor unit, often referred to as the condenser, which 

contains the compressor, condenser coil, and a condenser fan to blow ambient air over the coil. 

Packaged systems contain all of these components in a single unit. 

EPCA defines a “central air conditioner” as “a product, other than a packaged terminal 

air conditionera

A residential central heat pump utilizes the same components as central air conditioner, 

but it also has a reversing valve. The reversing valve switches the direction of the refrigerant 

flow and allows for the system to provide heating during the winter months in addition to cooling 

during the summer.

, which is powered by single-phase electric current, air cooled, rated below 

65,000 Btu per hour, not contained within the same cabinet as a furnace, the rated capacity of 

which is above 225,000 Btu per hour, and is a heat pump or a cooling only unit.” (42 U.S.C. 

6291(21)(A)-(E)) DOE has incorporated this definition into its regulations at 10 CFR 430.2.

EPCA defines a “heat pump” as “a product, other than a packaged terminal heat pumpb, 

which consists of one or more assemblies, powered by single-phase electric current, rated below 

65,000 Btu per hour, utilizing an indoor conditioning coil, compressor, and refrigerant-tooutdoor air heat exchanger to provide air heating, and may also provide air cooling, 

dehumidifying, humidifying circulating, and air cleaning.” (42 U.S.C. 6291(24)(A)-(E)) DOE 

has incorporated this definition into its regulations at 10 CFR 430.2.These products, also called 

unitary air conditioners and heat pumps, are limited to cooling capacities of less than 65,000 

Btu/hr (5.4 tons) and do not include room air conditionersc

 a “Packaged terminal air conditioner” is defined in 10 CFR 430.2 as “a wall sleeve and a separate unencased 

combination of heating and cooling assemblies specified by the builder and intended for mounting through the wall. 

It includes a prime source of refrigeration, separable outdoor louvers, forced ventilation, and heating availability 

energy.” 

b .” “Packaged terminal heat pump” is defined in 10 CFR 430.2 as “a packaged terminal air conditioner that utilizes 

reverse cycle refrigeration as its prime heat source and should have supplementary heating availability by builder’s 

choice of energy.” For more information on package terminal air conditioners and heat pumps, see 

http://www.eere.energy.gov/buildings/appliance_standards/commercial/packaged_ac_hp.html. c “Room air conditioner” is defined in 10 CFR 430.2 as “a consumer product, other than a ‘packaged terminal air 

conditioner,’ which is powered by a single phase electric current which is an encased assembly designed as a unit 

for mounting in a window or through the wall for the purpose of providing delivery of conditioned air to an enclosed 
3-4

DOE’s current standards for central air conditioners are expressed as minimum seasonal 

energy efficiency ratio (SEER) and SEER and heating seasonal performance factor (HSPF) for 

heat pumps. SEER is a seasonal efficiency metric that fully accounts for fuel consumption in 

active, standby, and off modes during the cooling season, while HSPF is a seasonal efficiency 

metric that fully accounts for active, standby and off modes for heat pumps during the heating 

season. For this rulemaking, DOE is considering energy efficiency ratio (EER) for one trial 

standard level (TSL) as well because this metric is part of a consensus agreement and would 

provide additional energy savings. DOE published a test procedure SNOPR in the Federal 

Register on April 1, 2011, that proposes to amend DOE’s test procedure for air conditioners and 

heat pumps to establish a method for measuring the electrical energy use in standby mode and 

off mode for air conditioners and heat pumps during the time, which is not already accounted for 

in the SEER or HSPF metrics. 76 FR 18105. 

3.1.2 Product Classes

3.1.2.1 Furnaces

DOE categorized the furnaces into product classes and will formulate a separate amended 

energy conservation standard for each product class in this rulemaking. EPCA specifies the 

criteria for product class separation, which includes: (1) the type of energy consumed; (2) 

capacity; or (3) other performance-related features, such as those that provide utility to the 

consumer or other features deemed appropriate by the Secretary that would justify the 

establishment of a separate energy conservation standard. (42 U.S.C. 6295(q))

Because the current residential furnaces market is very similar to the market that existed 

for the November 2007 residential furnaces rulemaking in terms of the types of products 

available, DOE continued to use the product classes established in that rulemaking. The 

November 2007 Rule divided products by fuel type (i.e., gas, oil-fired, electric) and by 

performance-related features, such as whether they were weatherized (i.e., intended for outdoor 

installation) or non-weatherized (i.e., intended for indoor installation). The November 2007 Rule 

also considered mobile home furnaces as a separate product class due to the unique size and 

venting constraints that are placed on those products. Therefore, the product classes that DOE is

considering in this rulemaking for amended AFUE minimum energy conservation standards are: 

non-weatherized gas furnaces, mobile home gas furnaces, and non-weatherized oil-fired 

furnaces. DOE also considered weatherized gas furnaces and electric furnaces, but determined 

that for weatherized gas furnaces, the November 2007 Rule set the standards at the max-tech 

level; and that electric furnaces on the market have efficiencies already approaching 100 percent 

AFUE and, as a result, have no methods available to increase the AFUE of these products. DOE 

will also analyze these product classes for its maximum allowable standby and off mode energy 

consumption standards analyses. These product classes and their characteristics are shown in 

Table 3.1.1.

 space. It includes a prime source of refrigeration and may include a means for ventilating and heating.” For more 

information on room air conditioners, see 

http://www.eere.energy.gov/buildings/appliance_standards/residential/room_ac.html.
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Table 3.1.1 Product Classes for Residential Furnaces Used in this Rulemaking

Product Class Characteristics

Non-weatherized gas furnace Intended for indoor installation; fueled by natural gas

Weatherized gas furnace Intended for outdoor installation; only sold as gas/electric 

packaged units with air conditioners; fueled by natural gas

Mobile home gas furnace Intended for mobile home installation; require direct vent; 

subject to space constraints; fueled by natural gas

Non-weatherized oil-fired furnace Intended for indoor installation; fueled by heating oil

Electric furnace Intended for indoor or outdoor installation; provide heat using 

electric resistance heating elements

3.1.2.2 Central Air Conditioners and Heat Pumps

Residential central air conditioners and heat pumps are divided into nine product classes 

based on physical characteristics of the product that affect performance. Key physical 

characteristics include product type (i.e., air conditioner or heat pump), whether the unit is a 

single package or has individual indoor and outdoor sections, and space constraints that relate to 

product utility.

The existing Federal energy conservation standards for residential central air conditioners 

and heat pumps went into effect on January 23, 2006. 10 CFR Part 430.32(c)(2) lists the nine 

product classes of residential central air conditioners and heat pumps and their corresponding 

energy conservation standards. The product classes are:

• Split-system air conditioners

• Split-system heat pumps

• Single-package air conditioners

• Single-package heat pumps

• Through-the-wall air conditioners and heat pumps – split system

• Through-the-wall air conditioners and heat pumps – single package

• Small duct, high velocity systems

• Space-constrained air conditioners

• Space-constrained heat pumps

For this residential central air conditioner and heat pump rulemaking, DOE maintained 

the existing product classes. However, two of the existing product classes, through-the-wall air 

conditioners and heat pumps – split system and through-the-wall air conditioners and heat pumps 

– single package, no longer existd

 d As defined in 10 CFR 430.2, the through-the-wall product class applies only to products manufactured prior to 

January 23, 2010. This provision eliminates through-the-wall units as a separate product class after this date.

. Therefore, DOE did not consider those two product classes 

separately (instead DOE considered them to be space-constrained products) and examined only
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seven product classes for this residential central air conditioner and heat pump rulemaking. The 

seven product classes DOE examined are:

• Split-system air conditioners

• Split-system heat pumps

• Single-package air conditioners

• Single-package heat pumps

• Small duct, high velocity systems

• Space-constrained air conditioners

• Space-constrained heat pumps

3.1.3 Test Procedures

3.1.3.1 Furnaces

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

annual fuel utilization efficiency (AFUE) as measured by the DOE test procedure. (42 U.S.C. 

6295(f)(1-2)) DOE’s test procedure for residential furnaces is described in Appendix N to 

Subpart B of 10 CFR part 430, which incorporates by reference American National Standards 

Institute/American Society of Heating, Refrigerating and Air-Conditioning Engineers 

(ANSI/ASHRAE) Standard 103-2007 Method of Testing for Annual Fuel Utilization Efficiency 

of Residential Central Furnaces and Boilers. AFUE is the ratio of annual output of useful heat to 

annual fuel input energy, and it includes active mode, standby, and off mode fuel consumption 

(including non-heating-season pilot input loss if applicable). 

For gas and oil-fired furnaces, AFUE does not account for electrical energy consumption 

in standby mode and off mode, although it does address fossil fuel use in these modes. For 

electric furnaces, AFUE also does not account for electrical energy consumption in standby 

mode and off mode. To satisfy the requirements of EPCA as amended by EISA, the DOE test 

procedure for residential furnaces and boilers was amended by a final rule published on October 

20, 2010, to account for standby and off mode electrical energy consumption. 75 FR 64621. The 

amended DOE test procedure incorporates by reference provisions of the International 

Electrotechnical Commission (IEC) Standard 62301, “Household electrical appliances—

Measurement of standby power” (“IEC 62301”). It also adds new calculations to determine the 

annual energy consumption associated with standby mode and off mode measured power, and it 

modifies the existing energy consumption equations to integrate standby mode and off mode 

electrical energy consumption into the calculation of overall annual energy consumption of these 

products.

3.1.3.2 Central Air Conditioners and Heat Pumps

The test procedures for central air conditioners and heat pumps are codified in 10 CFR 

430, Subpart B, Appendix M. Most aspects of the existing test procedure for central air 

conditioners and heat pumps date back to its original publication in the Federal Register on 

December 27, 1979. 44 FR 76700. DOE modified the test procedure on March 14, 1988, to cover 

variable-speed central air conditioners and heat pumps, to address testing of split non-ducted 
3-7

units, and to change the method used for crediting heat pumps that provide a demand defrost 

capability. 53 FR 8304.

A further revision of the test procedure for central air conditioners and heat pumps was 

published as a final rule on October 11, 2005, and became effective on April 10, 2006. 70 FR 

59122. Generally, the October 2005 final rule added new sections, revised several sections, and 

re-organized the test procedure in order to eliminate the need for several test procedure waivers 

and to make the test procedure more chronological in its progression. The revisions to the test 

procedure did not alter the minimum energy conservation standards in effect for central air 

conditioners and heat pumps. On July 20, 2006, DOE published a proposed rule to consider 

further changes to the test procedure in response to issues raised by stakeholders prior to the 

publication of the October 11, 2005, final rule. 71 FR 41320. DOE determined that it was 

appropriate to consider additional modifications to the test procedure for the following reasons:

(1) to implement test procedure revisions that are needed because of new energy conservation 

standards for small-duct, high-velocity (SDHV) systems; (2) to better address test procedure 

waivers for multi-split systems; and (3) to address sampling and rating issues that have been 

raised since new minimum energy conservation standards for these products became effective on 

January 23, 2006. Id. at 41321-22. A final rule adopting additional amendments to the central air 

conditioner and heat pump test procedures related to these issues was published on October 22, 

2007, which became effective on April 21, 2008. 72 FR 59906. Subsequent waivers granted for

residential modulating multi-split systems terminated on the effective date of the latest test

procedure final rule. 72 FR at 59906-07. EISA 2007 amended EPCA to require DOE to regulate 

standby and off mode power consumption (42 U.S.C. 6295(gg)(3)); and DOE is currently 

conducting another test procedure rulemaking to address off mode as well as other test procedure 

issues. A NOPR was published on June 2, 2010 and a final rule is slated for publication in spring 

2011. 75 FR 21224-31271. 

3.2 MARKET ASSESSMENT

The following market assessment identifies manufacturer trade associations, domestic

and international manufacturers of residential central air conditioners and heat pumps and their 

corresponding market shares, and regulatory and non-regulatory programs. The market 

assessment also describes the cost structure for the residential central air conditioner and heat 

pump industry and summarizes relevant market performance data.

3.2.1 Trade Associations

AHRI is a national trade association of manufacturers of residential, commercial, and 

industrial appliances, equipment, components, and related products. AHRI was established in 

January 2008 when the Air-Conditioning and Refrigeration Institute (ARI) merged with the Gas 

Appliance Manufacturers Association (GAMA). AHRI’s member companies are responsible for

over 90 percent of the residential and commercial air conditioning and space heating equipment 

sold in North America.5 AHRI develops and publishes technical standards for residential and 

commercial equipment using rating criteria and procedures for measuring and certifying 

equipment performance. AHRI also participates in developing international standards and has 

established a policy of adopting international standards for use in the United States when 

technologically and economically feasible.
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AHRI administers the GAMA Certificatione

AHRI also administers the ARI Performance Certified program that tests and certifies the 

performance of central air conditioners and heat pumps. AHRI maintains the AHRI Directory of 

Certified Product Performance that lists all products that have been certified by the AHRI. AHRI 

maintains certified performance directories for both air conditioners and heat pumps rated below 

65,000 Btu/h. The AHRI directories subdivide these products based upon certain defining 

characteristics, such as single package or split system and coil only or coil and blower 

combinations. 

program that tests and certifies the 

performance of gas- and oil-fired central furnaces that use single-phase electric current or DC 

and that have a heat input rate of less than 225,000 Btu/h. AHRI maintains the AHRI Directory 

of Certified Product Performance that lists all products that have been certified by the AHRI. 

Table 3.2.1 shows the AHRI classifications where products are available in the 

AHRI directories of certified products, along with the corresponding DOE product classes for 

this rulemaking.

 e The GAMA Efficiency Rating Certified mark is being phased out of use by January 1, 2012, and will be replaced 

by the AHRI Certified mark.
3-9

Table 3.2.1 AHRI Directory of Certified Product Performance Classifications for 

Residential Central Air Conditioners and Heat Pumps

DOE Product Class AHRI Classifications*

Split system air conditioners RCU-A-C

RCU-A-CB

RCU-A-CB-O

RCUY-A-CB

RCUY-A-CB-O

RC-A

Split system heat pumps HRC-A-C

HRC-A-CB

HRCU-A-C

HRCU-A-CB

HRCU-A-CB-O

HORC-A-C

HORCU-A-C

HORCU-A-CB

Single package air conditioners SP-A

SPY-A

Single package heat pumps HSP-A

Small duct, high velocity systems SDHV-RCU-A-CB

SDHV-HRCU-A-CB

SDHV-HORCU-A-CB

Space constrained products – air conditioners** TTW-RCU-A-C

TTW-RCU-A-CB

Space constrained products – heat pumps** TTW-HRCU-A-C

TTW-HRCU-A-CB

*The classifications listed are only those with products available in the AHRI Directories of Certified Product 

Performance for central air conditioners and heat pumps. For more information on AHRI classifications and their 

definitions, visit www.ahridirectory.org/ahriDirectory/pages/fieldHelp.aspx?program=AC&controlID=ariType for

air conditioners, or www.ahridirectory.org/ahriDirectory/pages/fieldHelp.aspx?program=HP&controlID=ariType for

heat pumps.

**On January 23, 2010, the through-the-wall equipment classes expired, at which time, they became part of the 

space constrained product classes.

HARDI is an international trade organization that represents over 450 wholesale 

companies in the HVAC industry, including 17 international companies, plus over 300 

manufacturing associates and nearly 140 manufacturer representatives. HARDI estimates that its 

members represent 80 percent of the dollar value of the HVACR products sold through 

distribution. The organization is a recent consolidation of the Northamerican Heating, 

Refrigeration & Airconditioning Wholesalers (NHRAW) and Air-conditioning & Refrigeration 

Wholesalers International (ARWI).6

ACCA is a nationwide trade organization that represents over 4,000 air conditioning 

contractors. ACCA supports the HVACR industry by bringing contractors together and

providing technical, legal, and marketing resources. ACCA is “the only nationwide organization 

of, by and for the small businesses that design, install and maintain indoor environmental 

systems.”7
3-10

3.2.2 Manufacturers and Market Share

DOE examined its database of residential furnaces, manufacturers’ websites, and product 

catalogs to identify residential furnace manufacturers. All manufacturers listed in DOE’s 

database for residential furnaces are shown in Table 3.2.2. Manufacturers may offer multiple 

brand names. DOE identified more than 50 brands under which furnaces are manufactured and 

marketed. 
3-11

Table 3.2.2: Manufacturers Whose Products are Included in DOE's Database*

Manufacturer Parent Company (if 

applicable) NWGF WGF MHGF NWOF

Adams Manufacturing Company N/A X

Airwell-Fedders North America, 

Inc. Elco Holdings Ltd. X

Airxcel Holdings, Inc. Bruckmann, Rosser, 

Sherrill & Co. L.L.C.

Bard Manufacturing Company N/A X X

Boyertown Furnace Company N/A X

Carrier Corporation United Technologies 

Corporation X X X X

Crown Boiler Company Burnham Holdings, Inc. X X

ECR International N/A X X

EFM Sales Company General Machine 

Corporation X

Goodman Manufacturing Company Goodman Global 

Group, Inc. X X

H.E.P. Materials Corp. AllStyle Coil Company, 

L.P.

Haier America Haier Group Company X

Heat Controller, Inc. N/A X

Kerr Energy Systems Granby Industries 

Limited Partnership X

Lennox Industries, Inc. Lennox International, 

Inc. X X X

National Comfort Products N/A X

Newmac Manufacturing, Inc. William Newport 

Holdings Limited X

Nordyne, Inc. Nortek, Inc. X X X X

Rheem Manufacturing Company Paloma Group X X X

Texas Furnace, LLC AllStyle Coil Company, 

L.P. X

Thermo Products, LLC Burnham Holdings, Inc. X X X

Trane Inc. Ingersoll Rand X X X X

York International Corporation Johnson Controls, Inc. X X X X

Weil-McLain SPX Corporation

Whirlpool Home Cooling and 

Heating Whirlpool Corporation X X
3-12

Wolf Steel Ltd. N/A X

* Airwell-Fedders North America, Inc., owned by Israeli parent company Elco Holdings Ltd., refers to 

Fedders, Eubank, and Airtemp products. Airxcel Holdings, Inc. is owned by private equity firm 

Bruckmann, Rosser, Sherrill & Co. L.L.C. and refers to subsidiaries Marvair and Suburban Manufacturing 

Company. Carrier Corporation is owned by United Technologies Corporation and refers to its subsidiaries: 

Carrier North America Home Comfort, Bryant Heating and Cooling Systems, International Comfort 

Products (ICP), Payne Heating and Cooling Systems, and Day & Night Heating and Cooling Products. 

Brands under ICP include: Heil, Tempstar, Arcoaire, Comfortmaker, Airquest, KeepRite, and Lincoln. 

ECR International includes Climate Energy, LLC and Oneida Royal. Goodman Manufacturing Company is 

a division of Goodman Global, Inc. and primarily markets its products under the Goodman and Amana 

brand names. Haier America is a subsidiary of the Haier Group Company. Heat Controller, Inc. 

manufactures and distributes the Comfort-Aire and Century brands. Lennox Industries, Inc., a subsidiary of 

Lennox International Inc., includes Lennox, Armstrong Air, AirEase, Concord, Ducane Air Conditioning 

and Heating, Allied Commercial, and Magic-Pak. Newmac Manufacturing, Inc. is a subsidiary of William 

Newport Holdings Limited. Nordyne, Inc. is a subsidiary of Nortek Incorporated and manufactures 

furnaces under the following brands: Broan, Elect-Aire, Frigidaire, Garrison, Gibson, Grandaire, 

Intertherm, Kelvinator, Maytag, Miller, Nutone, Philco, Tappan, Thermal Zone, and Westinghouse. Rheem 

Manufacturing Company refers to Rheem Manufacturing Company, Rheem Air Conditioning Division, 

Rheem Sales Company, Inc., and Ruud Air Conditioning Division. All Rheem and Ruud companies are 

subsidiaries of the Paloma Group. Sears, Roebuck and Company is a subsidiary of the Sears Holdings 

Corporation. Texas Furnace, LLC is a subsidiary of AllStyle Coil Company, L.P. Crown Boiler Company 

and Thermo-Products, LLC are owned by Burnham Holdings, Inc. Trane Inc. manufactures products under 

the American Standard and Trane brand names. Ingersoll Rand owns Trane. York International Corporation 

refers to the following brands: Coleman, Evcon, Fraser-Johnston, Guardian, Luxaire, and York. York 

International Corp. is owned by Johnson Controls. Weil-McLain, which includes Williamson-Thermoflo, is 

a division of SPX Corporation. Whirlpool Home Cooling and Heating is a division of the Whirlpool 

Corporation. Wolf Steel Ltd. also does business as Napoleon Fireplaces.

The domestic gas furnace market is almost entirely held by seven U.S. manufacturers: 

Carrier, Goodman, Lennox, Tranef

, Rheem, York, and Nordyne.8 Figure 3.2.1 shows the 2008 

market shares for residential furnace manufacturers as depicted in the September 2009 issue of 

Appliance Magazine.

 f Prior to 2007, Trane was a subsidiary of American Standard Companies. On November 28, 2007 Trane separated 

from the two other branches of American Standard Companies. On June 5, 2008, Ingersoll Rand acquired Trane. For 

more information, visit www.trane.com/Corporate/About/history.asp.
3-13

Figure 3.2.1 2008 Market Shares for U.S. Manufacturers of Residential Gas Furnaces9

Two of these major manufacturers, Nordyne and York, are also major players in the 

market for mobile home gas furnaces. Other manufacturers of mobile home gas furnaces include 

Trane, Carrier, and Thermo Pride.

In contrast to the gas furnace market, the U.S. residential oil-fired furnace market is 

composed almost entirely of small manufacturers. Small manufacturers include Adams, Bard, 

Boyertown, Crown Boiler, ECR International, EFM, Kerr, and Newmac; larger manufacturers 

include Thermo Pride and Lennox. Some of the large gas furnace manufacturers (including 

Carrier, Nordyne, Rheem, Trane, and York) also market oil-fired furnaces, although these 

furnaces are typically rebranded units from another original equipment manufacturer (OEM). 

DOE estimated the market shares of oil-fired furnace manufacturers based on publicly available 

information and manufacturer feedback. Manufacturers with an estimated market share of greater 

than or equal to 10 percent were designated as major players in the oil-fired furnace market, 

while manufacturers with an estimated market share of less than 10 percent were designated as 

minor players in the market. These manufacturers are shown in Table 3.2.3.

Table 3.2.3 Manufacturers of Residential Oil-Fired Furnaces

Major Manufacturers* Minor Manufacturers*

Lennox

Thermo Pride

ECR International

Adams

Bard

Boyertown

Crown Boiler

EFM

Kerr

Newmac

*”Major manufacturers” are estimated to have at least 10 percent market share, while “minor manufacturers” are 

estimated to have less than 10 percent market share.

Carrier

32%

Goodman

Lennox 15%

13%

Trane

13%

Rheem

12%

York

9%

Nordyne

5%

Others

1%
3-14

Many of the residential furnace manufacturers fabricate central air conditioners and heat 

pumps as well. DOE examined AHRI’s Directory of Certified Product Performance for 

residential central air conditioners and heat pumps to identify residential central air conditioner 

and heat pump manufacturers. DOE identified 45 separate companies that manufacture and 

market air conditioner and heat pump systems and coils. The manufacturers found in the AHRI 

Directories of Certified Product Performance for residential central air conditioners and heat 

pumps are listed in Table 3.2.4, along with their parent company in parentheses, if applicable.

Table 3.2.4 Manufacturer Brand Names Found in the AHRI’s Directories of Certified 

Product Performance for Residential Central Air Conditioners and Heat Pumps10

Aaon, Inc. Lennox International National Coil Company

Aire-Flo Friedrich Air Conditioning Co. (US 

Natural Resources, Inc.)

National Comfort Products 

(National Refrigeration and Air 

Conditioning Products, Inc.)

Airquest Fujitsu General America, Inc. (Fujitsu 

General Group)

Nutone

Airwell-Fedders North America, 

Inc.

GD Midea Commercial AirConditioning Equipment Co., Ltd.Quietside

Bard Manufacturing Company Goodman/Amana (Goodman Global, 

Inc.)

Rheem/Ruud (Paloma Global)

Beutler Corporation Grandaire Style Crest Products

Broan Haier America (Haier Group) Summit Manufacturing, Inc.

Century (Heat Controller) Heat Controller, Inc. Texas Furnace, LLC

Cold Point Corp. Intertherm Thermo Products, Inc. (Burnham 

Holdings, Inc.)

Dayton Electric Manufacturing 

Company (WW Grainger, Inc.)

Kenmore (Sears Holdings Corporation) Trane/American Standard 

(Ingersoll Rand)

Eair LLC LG Electronics, Inc. Unitary Products Group 

(York/Johnson Controls)

Ecotemp Mammoth, Inc. (Thomas H. Lee 

Partners, LP)

United Refrigeration Distributors, 

Inc.

Enviromaster International (ECR 

International, Inc.)

McQuay International (Daikin 

Industries, Ltd.)

V-Aire

Espitech, LLC Mitsubishi Electric and Electronics 

USA, Inc.

Whirlpool

International Comfort Products -

Carrier/UTC

Nordyne Xenon

Figure 3.2.2 displays the 2007 market shares for the residential central air conditioner 

market. The seven largest residential gas furnace manufacturers also dominate the residential 

central air conditioner and heat pump industry. These seven manufacturers include Carrier, 
3-15

Goodman, Traneg, Lennox, Rheem, York, and Nordyne and control 97 percent of the central air 

conditioner and heat pump market, as of 2008. 

Figure 3.2.2 2008 Market Shares for Unitary Air Conditioners and Heat Pumps11

3.2.2.1 Mergers and Acquisitions

A trend in the both the residential furnace industry and the residential central air 

conditioning and heat pump industry over the past decades has been the consolidation of major 

manufacturers. In the last ten years or so, the seven major manufacturers (i.e., Goodman, 

Lennox, Carrier, York, Rheem, Nordyne, and Trane) have gone through various mergers and

acquisitions, and have materialized as differentiated leaders in the air conditioning and heat 

pump manufacturing industry. A brief summary of the recent history of each of the seven largest 

manufacturers is as follows:

• Goodman Global, Inc. was founded and purchased Janitrol in 1982. In 1997, 

Goodman acquired Amana, which was then sold to Maytag in 2001, and later to 

Whirlpool when Whirlpool acquired Maytag in 2006.

• Lennox Industries is a subsidiary of Lennox International, Inc., a holding company 

that was created in 1984. Lennox International acquired Armstrong Air Conditioning 

Inc. in 1988. In 1999, Lennox International completed an Initial Public Offering and 

 g Prior to 2007, Trane was a subsidiary of American Standard Companies. On November 28, 2007 Trane separated 

from the two other branches of American Standard Companies. On June 5, 2008, Ingersoll Rand acquired Trane. For 

more information, visit www.trane.com/Corporate/About/history.asp.

UTC/Carrier

27%

Goodman 

(Amana)

14%

American 

Standard 

(Trane)

14%

Lennox

12%

Rheem

12%

York 

9%

Nordyne 

9%

Others

3%
3-16

became a public company12

• Carrier has been a wholly-owned subsidiary of United Technologies Corporation 

since 1979. In 1999, Carrier Corporation acquired International Comfort Products 

(ICP).

. Around this time, Lennox also acquired Service Experts 

and other equipment service companies.

13

• York Unitary Products Group and York International are subsidiaries of Johnson 

Controls, Inc. Johnson Controls, Inc. purchased York in 2005. 14

• Rheem is a privately held firm that was acquired by Paloma Industries of Japan in 

1987. Paloma Industries also acquired Rheem Australia (Solahart) in 2002. 15

• Nordyne is a subsidiary of the privately held Nortek, Inc. 16

• Trane Inc. was acquired by American Standard Companies in 1984. In 2007 Trane 

separated from American Standard and was subsequently bought by Ingersoll-Rand in 

2008.

3.2.2.2 Small Businesses

DOE considers the possibility of small businesses being particularly impacted by the 

promulgation of minimum energy conservation standards for residential central air conditioners

and heat pumps. The Small Business Administration (SBA) defines small business 

manufacturing enterprises for residential central air conditioners and heat pumps as having 750 

employees or fewer.

17

DOE further studied the potential impacts on these small businesses in detail and 

presented the results in manufacturer impact analysis (MIA) (Chapter 12 of this TSD). DOE has 

identified the following as either small business furnace manufacturers or small business 

residential central air conditioner and heat pump manufacturers with the small business parent 

companies in parentheses if applicable:

SBA lists small business size standards that are matched to industries as 

they are described in the North American Industry Classification System (NAICS). A size 

standard is the largest that a for-profit concern can be and still qualify as a small business for 

Federal Government programs. These size standards are generally the average annual receipts or 

the average employment of a firm. For both residential furnaces and residential central air 

conditioners and heat pumps, the size standard is matched to NAICS code 333415, AirConditioning and Warm Air Heating Equipment and Commercial and Industrial Refrigeration 

Equipment Manufacturing, which has a size standard of 750 employees.

• Adams Manufacturing Company

• Aerosys

• Bard Manufacturing Company

• Boyertown Furnace Company

• Eair, LLC

• ECR International

• EFM

• Espitech, LLC

• H.E.P. Materials Corp. (AllStyle Coil Company)

• Heat Controller, Inc.

• National Coil Company
3-17

• National Comfort Products

• Newmac Manufacturing, Inc. (William Newport Holdings Limited)

• Texas Furnace, LLC (AllStyle Coil Company)

3.2.3 Distribution Channels

A single distribution channel represents the vast majority of the HVAC market. Simply, 

the OEM assembles the system and sells it to a distributor; the distributor warehouses and 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. Some manufacturers use a “direct-to-dealer” model in 

which the manufacturer sells to a contractor and the contractor sells the unit to the final 

consumer. The final consumer varies in the replacement and in the new construction market. In 

the replacement market, the final consumer is usually the homeowner, as illustrated in Figure 

3.2.2 and Figure 3.2.3, 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. Replacements represent approximately 75 percent of nonweatherized gas furnace sales, 50 percent of mobile home gas furnace sales, and 90 percent of oil 

furnace sales in the United States.

18

Figure 3.2.4

In the new construction market, a builder or general 

contractor is effectively the final end-user, as shown in . In the new construction 

market, the home builder has a much stronger influence than the homeowner, who typically has 

little choice in what kind of system is installed. The new construction market tends to be a lowcost, low-efficiency market, as the decision-makers are not the beneficiary of the system 

installed. After installation, mechanical contractors typically perform additional lifecycle service 

on the system, including inspection, maintenance, and repair. 

Figure 3.2.3 Traditional Distribution Chain in Replacement Market

Figure 3.2.4 Direct-to-Dealer Distribution Chain in Replacement Market

Figure 3.2.5 Distribution Chain in New Construction Market

Manufacturer Distributor Dealer Homeowner

Manufacturer Dealer Homeowner

Manufacturer Distributor General Contractor (Installed 

by Mechanical Contractor)
3-18

3.2.4 Regulatory Programs

The following section details current regulatory programs mandating energy conservation 

standards for residential furnaces and residential central air conditioners and heat pumps. Section 

3.2.3.1 discusses current Federal energy conservation standards. Sections 3.2.3.2 and 3.2.3.3

review standards in both Canada and Mexico that may impact the companies servicing the North 

American market.

3.2.4.1 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 furnaces and residential central air 

conditioners and heat pumps. (42 U.S.C. 6291-6309) The current Federal standards prescribed by 

EPCA have applied since January 1, 1990, for mobile home furnaces and January 1, 1992, for all 

other furnaces except “small” furnaces. (42 U.S.C. 6295(f)(1)–(2)) Table 3.2.5 presents the 

current Federal energy conservation standards for residential furnaces as prescribed by section 

325(f) of EPCA. 

Table 3.2.5 Current Federal Energy Conservation Standards Established by EPCA, as 

Amended by NAECA

Product Class Minimum AFUE

%

Furnaces (excluding classes noted 

below) 78

Mobile home furnaces 75

Small furnaces (having an input rate 

of less than 45,000 Btu/h) 78

Pursuant to 42 U.S.C. 6295(f)(4)(B), DOE amended the energy conservation standards 

for residential furnaces in a final rule issued on November 19, 2007 (hereafter referred to as the 

November 2007 Rule). 72 FR 65135. These standards, shown in Table 3.2.6, have a compliance 

date of November 19, 2015, prior to the compliance date of this rulemaking (unless DOE adopts 

the levels and compliance dates in the consensus agreement). Because they will be the minimum 

energy efficiency standards at the time of this rulemaking’s compliance date, DOE has adopted 

them as the baseline efficiency levels for its analyses, as discussed in the final rule.

Table 3.2.6 Federal Energy Conservation Standards Established by the November 2007 

Rule

Product Class Minimum AFUE

%

Non-weatherized gas furnaces 80

Weatherized gas furnaces 81

Mobile home gas furnaces 80

Non-weatherized oil-fired furnaces 82
3-19

The most recent Federal standards for residential central air conditioners and heat pumps 

went into effect on January 23, 2006, and are codified in 10 CFR Part 430.32. Table 3.2.7

presents the current Federal energy conservation standards for residential central air conditioners 

and heat pumps as presented in part (c)(2) of 10 CFR Part 430.32.

Table 3.2.7 Current Federal Energy Conservation Standards for Residential Central Air 

Conditioners and Heat Pumpsh

Product class SEER HSPF * **

(i) Split system air conditioners 13.0 -

(ii) Split system heat pumps 13.0 7.7

(iii) Single package air conditioners 13.0 -

(iv) Single package heat pumps 13.0 7.7

(v)(A) Through-the-wall air conditioners and heat pumps-split 

system

10.9

†

7.1

(v)(B) Through-the-wall air conditioners and heat pumps-single 

package

10.6

†

7.0

(vi) Small duct, high velocity systems 13.0 7.7

(vii)(A) Space constrained products-air conditioners 12.0 -

(vii)(B) Space constrained products-heat pumps 12.0 7.4 * SEER is seasonal energy efficiency ratio.

** HSPF is heating seasonal performance factor.

†

3.2.4.2 Canadian Energy Conservation Standards

As defined in 10 CFR Part 430.2, this product class applies to products manufactured before January 23, 2010.

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

mandates minimum energy conservation standards for residential furnaces and residential central 

air conditioners and heat pumps that apply to imports and interprovincial trade. The standards 

for furnaces 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). These 

standards apply to automatic operating gas-fired central forced-air furnaces that use propane or 

natural gas and have an input rate not exceeding 225,000 Btu/h, but do not apply to furnaces for 

mobile homes or recreational vehicles. The furnace standards and their compliance dates are 

shown in Table 3.2.9, while the air conditioner and heat pump standards are contained in Table 

3.2.9 and became effective in November 2006.

 h Current Federal energy conservation standards for residential central air conditioners taken from 10 CFR 

430.32(c)(2).
3-20

Table 3.2.8 Canadian Energy Conservation Standards for Residential Gas Furnaces19

Product

Minimum AFUE 

Standard

%

Compliance Date

Gas furnaces, other than those with an 

integrated cooling component that are 

outdoor or through-the-wall* gas furnace, 

that have an input rate no greater than 

225,000 Btu/h and that use single-phase 

electric current

90 On or after 

December 31, 2009

Gas furnaces that are outdoor furnaces with 

an integrated cooling component, that have 

an input rate no greater than 225,000 Btu/h 

and that use single-phase electric current

78 On or after 

December 31, 2009

Gas furnaces that are through-the-wall with 

an integrated cooling component, that have 

an input rate no greater than 225,000 Btu/h 

and that use single-phase electric current

78

On or after 

December 31, 2009 

until December 30, 

2012

Gas furnaces that are through-the-wall with 

an integrated cooling component, that have 

an input rate no greater than 225,000 Btu/h 

and that use single-phase electric current

90 On or after 

December 31, 2012

*With respect to gas furnaces, “through-the-wall” refers to gas furnaces that are designed and marketed to 

be installed in an opening in an exterior wall that is fitted with a weatherized sleeve.

Table 3.2.9 Canadian Energy Conservation Standards for Residential Central Air 

Conditioners and Heat Pumps20

Product Minimum Energy 

Performance Standard

Air Conditioners – single package & split-system – cooling SEER = 13

Heat Pumps – single package & split–system – cooling SEER = 13

Heat Pumps – single package & split system – heating HSPF V* = 6.7

AC & HP – through–the–wall, cooling – (until January 22, 2010) SEER = 10.9

AC & HP – through–the–wall, cooling – (after January 23, 2010) SEER = 12

Heat pumps – through–the–wall – heating – (until January 22, 2010) HSPF V = 6.2

Heat Pumps – through–the–wall – heating – (after January 23, 2010) HSPF V = 6.4

AC & HP – space–constrained – cooling SEER = 12

Heat pumps – space–constrained – heating HSPF V = 6.4

AC & HP – small duct, high velocity (SDHV) – cooling SEER = 11

Heat Pumps – small duct, high velocity (SDHV) – heating HSPF V = 5.9 * HSPF V is the Heating Seasonal Performance Factor – Region V. U.S. energy conservation standards specify 

HSPF as HSPF IV (i.e. HSPF – Region IV). HSPF V = HSPF IV/1.15.
3-21

3.2.4.3 Mexican Energy Conservation Standards

The National Commission for Energy Saving (CONAE)iis the agency responsible for 

developing, updating, and implementing Mexican official standards of energy efficiency.

CONAE published NOM-011-ENER-2006 (which updated previous standard effective in 2002) 

in June 2007. The standards prescribe minimum efficiencies for central, package, and split

system central air conditioners with cooling capacities between 30,000 and 65,000 Btu/hj at a 

minimum of 13 SEER.

k

Table 3.2.5 Mexican Energy Conservation Standards for Residential Central Air 

Conditioners21

Product Minimum Energy 

Performance Standard

Air Conditioners – single package & split-system – cooling SEER = 13

3.2.5 Non-Regulatory Programs

DOE identified several non-regulatory programs aimed at improving the energy 

efficiency of residential furnaces, central air conditioners and heat pumps. Two such programs 

are based on voluntary efficiency targets for residential central air conditioners and air-source 

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

initiative. In addition, DOE identified rebate programs and Federal and State tax credits for 

residential purchasers of higher-efficiency central air conditioners and heat pumps, and reviewed 

Federal procurement specifications for these products as well. 

3.2.5.1 ENERGY STAR

ENERGY STARl

Table 3.2.10

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 creates minimum energy efficiency 

specifications for various products, including split system and single package air conditioners 

and heat pumps. ENERGY STAR originally set specifications for central air conditioners and 

heat pumps in 1995, followed by revisions in 2002, 2006, and 2009. The current (2009) 

ENERGY STAR levels are shown in .

 i

For more information visit www.conae.gob.mx/wb/CONAE/english/_rid/6600?page=1. j

Cooling capacity is specified in the standard as 8,800W to 19,050W. k Mexican efficiency standards for central air conditioners are specified in terms of Relación de eficiencia energética 

estacional (REEE). NOM-011-ENER-2006 mandates a minimum efficiency of 3.81 REEE, which is equivalent to 

13 SEER. l

For more information, visit www.energystar.gov.
3-22

Table 3.2.10 ENERGY STAR Levels for Split System and Single Package Residential 

Central Air Conditioners and Heat Pumps 22

Product Class SEER Rating EER Rating HSPF Rating *

Split system air conditioners 14.5 12.0 -

Split system heat pumps 14.5 12.0 8.2

Single package air conditioners 14.0 11.0 -

Single package heat pumps 14.0 11.0 8.0 *

3.2.5.2 Consortium for Energy Efficiency

EER is energy efficiency ratio.

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 Residential Central Air Conditioner and 

Heat Pump Initiative promotes the use of high-efficiency residential central air conditioners and 

heat pumps, along with proper installation and sizing of these products. CEE identifies three tiers 

of efficiency for split system central air conditioners and two tiers of efficiency for split system 

heat pumps and single package central air conditioners and heat pumps. For split system central 

air conditioners and package central air conditioners and heat pumps, the CEE Tier 1 levels are 

the same as the ENERGY STAR levels. The CEE tier requirements are shown in Table 3.2.11.

Table 3.2.11 CEE Tiers for Residential Central Air Conditioners and Heat Pumps23

Product Class CEE Tier SEER 

Requirement

EER 

Requirement

HSPF 

Requirement

Split System Central Air Conditioners Tier 1 14.5 12.0 -

Tier 2 15.0 12.5 -

Tier 3 16.0 or higher 13.0 or higher -

Single Package Central Air Conditioners Tier 1 14.0 11.0 -

Tier 2 14.0 or higher 12.0 or higher -

Split System Heat Pumps Tier 1 14.5 12.0 8.5

Tier 2 15.0 or higher 12.5 or higher 8.5 or higher

Single Package Heat Pumps Tier 1 14.0 11.0 8.0

Tier 2 14.0 or higher 12.0 or higher 8.0 or higher

3.2.5.3 Consumer Rebate Programs

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

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

typically for existing home retrofits only. DOE maintains a database of such rebates, called the 

Database of State Incentives for Renewables & Efficiency (DSIRE), 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.

3.2.5.4 Federal Tax Credits

Until December 31, 2010, a Federal tax credit provides consumers a credit toward their 
3-23

Federal income tax if they purchase qualifying residential furnaces, central air conditioners or 

heat pumps. This tax credit applies only to products being installed in existing homes, not to 

furnaces, central air conditioners and heat pumps for new housing construction. This Federal tax 

credit is 30 percent of the installation cost (equipment and labor) to the consumer of the new 

system, with a maximum limit of $1,500. To qualify for the Federal tax credit, products must 

meet varying levels of efficiency depending on the product class. Table 3.2.12 and Table 3.2.13

describe the required efficiency level for each product class, along with the amount of the 

Federal tax credit available. 

Table 3.2.12 Federal Tax Credits for Residential Furnaces24

Product Requirement Available Tax 

Credit

Natural gas or 

propane furnace

≥ 95% AFUE 30% of cost, up to 

$1,500

Oil-fired furnace ≥ 90% AFUE 30% of cost, up to 

$1,500

Advanced main air 

circulating fan

< 2% of the 

furnace’s 

total energy

30% of cost, up to 

$1,500

Table 3.2.13 Federal Tax Credits for Residential Central Air Conditioners and Heat 

Pumps25

Product EER 

Requirement

SEER 

Requirement

HSPF 

Requirement Available Tax Credit

Central Air 

Conditioner – Split 

Systems

≥ 13.0 ≥16.0 N/A 30% of cost, up to 

$1,500

Central Air 

Conditioner – Single 

Package

≥12.0 ≥ 14.0 N/A 30% of cost, up to 

$1,500

Air Source Heat 

Pump – Split Systems ≥ 12.5 ≥15.0 ≥ 8.5 30% of cost, up to $1,500

Air Source Heat 

Pump – Single 

Package

≥ 12.0 ≥14.0 ≥8.0 30% of cost, up to 

$1,500

3.2.5.5 State Tax Credits

DOE also identified four states that have tax credits for residential furnaces: Montana, 

Orgeon, Indiana, and Kentucky. These same four states were also identified as having tax credits 

for central air conditioners and heat pumps.

Montana has had an Energy Conservation Tax Credit for residential energy conservation 

measures since 1998.26,27 The tax credit covers a variety of residential energy and water 

efficiency installations, including ENERGY STAR heating and cooling equipment. The amount 
3-24

of the credit increased in 2002 from 5 percent of equipment costs (up to $150) to 25 percent (up 

to $500 per taxpayer). The Energy Conservation Tax Credit can be used for equipment installed 

in new construction or remodeling projects, with the tax credit allowed only for the portion of the 

cost and materials above “established standards of construction.”

Table 3.2.14 State Tax Credits for Residential Gas Furnaces28

State

AFUE 

Requirement

%

Other Requirements Available 

Tax Credit

Oregon 92 Electrically-efficient 

fan motor, direct vent $350

Montana

Higher than the 

previous system, 

or exceeding 90*

N/A 25% of cost, 

up to $500

Indiana 90 N/A

20% of cost 

or $100, 

whichever is 

less

Michigan 90

Annual income of 

≤$37,500 for single 

filers and ≤$75,000 

for married couples 

filing jointly

10% of cost, 

up to $75 for 

single filers 

and $150 for 

joint filers

*Tax credit is available in new construction for investments that meet or exceed 

ENERGY STAR levels at 90% AFUE. In tax year 2009 exclusively, tax credit was 

available for replacements of an existing heating system with a new one of the same 

style or type that has a higher efficiency rating, whether or not the new heating system 

meets or exceeds the established standards for new construction or with a new system 

that is of a different style or type that exceeds the requirements for new construction.

Oregon’s Residential Energy Tax Credit (RETC) was created in 1977 to encourage the 

use of renewable resources in households. The Oregon legislature expanded the RETC program 

in 1997 to include residential refrigerators, clothes washers, and dishwashers; participation in the 

program increased significantly after they became eligible. The program subsequently added 

credits for high-efficiency heat pump systems, air conditioners, and water heaters (2001).

furnaces and boilers (2002), and other equipment and measures.29

To qualify, a central air conditioning or heat pump system must have a performance 

verification test by a tax credit-certified technician. For this verification test there is a separate 

tax credit of 25% of the cost of the test and any needed repairs, up to $250. Purchasers of highefficiency central air conditioners or heat pumps who have premium efficiency ducts qualify for 

an additional $150 tax credit.

Central air conditioning split-system units must have EER of 13.0 or higher. The tax 

credit for qualifying central air conditioning systems is the amount listed in Table 3.2.8 or 25 

percent of the net purchase price, whichever is less. 

29
3-25

Table 3.2.15 Oregon Tax Credit for Central Air Conditioners30

Tier Minimum Efficiency EER Maximum Tax Credit Amount

RAC4 13.0 $160

RAC5 14.0 $225

RAC6 15.0 $300

Air-source heat pump split-system equipment must have HSPF of 9.0 or higher and EER 

of 12 or higher. Table 3.2.9 shows the heat pump tax credit levels by system efficiencies.

Table 3.2.16 Oregon Tax Credits for Heat Pumps

HSPF Tax Credit Amount

At 12 EER At 12.5 EER At 13 EER

9.0 $300 $320 $340

9.5 $300 $360 $380

10.0 $300 $360 $430

Indiana offers a tax credit beginning in 2009 to individuals and small businesses for the 

costs associated with purchasing ENERGY STAR-qualified central air conditioners and other 

appliances. The credit may be claimed against the state income tax, insurance premium tax, or 

financial institutions tax. The amount of the tax credit is set at 20% of the expenditures for 

qualified heating and cooling equipment up to $100 per taxable year. The credit is for 

expenditures in 2009 and 2010 and there is no carryover.31,32

Kentucky offers a 30 percent state income tax credit beginning in 2009 for taxpayers who 

install certain energy efficiency measures on their principal residence or residential rental 

property. These energy efficiency measures include “Qualified Energy Property Installation,” 

which includes heat pumps and central air conditioners, among others. Equipment must meet the 

efficiency guidelines specified in the Federal tax credit for residential energy property (see Table 

3.2.7). The total annual tax credit for this equipment may not exceed $250. These credits apply to 

equipment purchased in taxable years 2009 to 2015 and may be carried forward for one year.33,34

3.2.5.6 FEMP Procurement Guidelines

DOE reviewed the Federal Energy Management Program (FEMP) procurement 

guidelines for Federal government equipment purchasing. The mission of DOE’s FEMP m is “to 

reduce the cost and environmental impact of the Federal government by advancing energy 

efficiency and water conservation, promoting the use of distributed and renewable energy, and 

improving utility management decisions at Federal sites.”35

FEMP designates standards for residential gas furnaces, central air conditioners and heat 

pumps purchased by the Federal government. The designated FEMP gas furnace standard level is 

FEMP helps Federal buyers identify 

and purchase energy-efficient equipment.

 m For more information, please visit www.eere.energy.gov/femp.
3-26

the ENERGY STAR level, or 90% AFUE.36 Table 3.2.10 shows the FEMP performance 

requirements for residential central air conditioners and Table 3.2.11 shows the requirements for 

air source heat pumps.37,38

Table 3.2.17 FEMP Performance Requirements for Residential Central Air Conditioners

System Type SEER EER

Split 14.5 or greater 12.0 or greater

Single package 14.0 or greater 11.0 or greater

Table 3.2.18 FEMP Performance Requirements for Air Source Heat Pumps

System Type HSPF EER SEER

Split 8.0 or greater 11.0 or greater 13.0 or greater

Single package 7.6 or greater 10.5 or greater 12.0 or greater

3.2.6 Industry Cost Structure

DOE developed an industry cost structure for residential central air conditioners and heat 

pumps from publicly available information from the Census Bureau’s ASM and the SEC 10-Kn

The Census Bureau collects industry-wide employment data based on NAICS codes. As 

stated previously, manufacturers of residential central air conditioners and heat pumps are 

grouped into the Air-Conditioning and Warm Air Heating Equipment and Commercial and 

Industrial Refrigeration Equipment Manufacturing category, which is NAICS code 333415. 

reports filed by publicly owned manufacturers. Companies subject to SEC regulations must 

report sales, costs of goods sold, gross profits, and various overhead costs, in addition to overall 

performance and operations for the year. DOE analyzed SEC 10-K reports from 2004 to 2008 

and developed a representative cost structure for the furnace industry. The cost of materials as a 

percentage of revenue for each product can fluctuate as raw material costs change from year to 

year. For more information on the furnace and central air conditioner industry cost structure

derived using SEC 10-K data, see chapter 12 of this TSD. 

Table 3.2.19 presents the residential air conditioning and warm air heating equipment 

manufacturing employment levels and earnings from 1997 to 2008 according to the NAICS.

 n For more information, please visit www.sec.gov.
3-27

Table 3.2.19 Air Conditioning and Warm Air Heating Equipment Industry Employment

and Payroll Data 39,40,41

Year Production Workers Total Number of

Employees

Payroll for All 

Employees

$, thousands

2008 70,772 96,502 4,010,045

2007 74,728 101,485 4,034,043

2006 74,909 98,097 4,019,813

2005 76,011 102,354 3,942,808

2004 73,106 99,035 3,691,029

2003 77,488 104,668 3,776,417

2002 80,417 108,274 3,815,747

2001 88,978 118,876 3,950,483

2000 97,978 127,384 4,267,872

1999 95,904 123,962 4,043,064

1998 91,994 120,011 3,844,667

1997 90,968 119,386 3,678,996

The statistics illustrate a steady decline in both the number of production and nonproduction workers in the industry after the year 2000, with the only exception being in 2005, 

when the number of employees increased. The overall decline in employment may be a result of 

industry consolidation, increased automation in production, or manufacturers moving their

facilities outside of the United States to reduce labor costs. The increase in employment in 2005 

may have resulted from manufacturers of residential central air conditioners in heat pumps 

augmenting the number of production workers to deal with the increased demand for central air 

conditioners and heat pumps that occurred prior to the most recent Federal standards becoming 

effective in 2006 (as shown by the sharp increase in residential central air conditioner and heat 

pump shipments in 2005).

Table 3.2.20 presents the costs of materials and industry payroll as a percentage of value 

of shipments from 1997 to 2006.
3-28

Table 3.2.20 Air Conditioning and Warm Air Heating Equipment Industry Cost Data 10,11

Percent of Value of Shipments

Year Cost of Materials Cost of Payroll for 

Production Workers Cost of Total Payroll

2006 53.2 8.9 13.8

2005 53.8 8.5 13.8

2004 51.1 8.8 14.2

2003 50.6 9.5 15.4

2002 49.4 9.8 15.9

2001 52.6 9.8 15.8

2000 53.0 10.1 16.0

1999 53.4 9.8 15.4

1998 54.9 9.9 15.4

1997 54.2 10.1 16.0

The cost of materials as a percentage of value of shipments has fluctuated slightly over 

the 10-year period. The cost of payroll for production workers as a percentage of value of 

shipments has followed a declining pattern since 1998, with the exception of only the year 2006, 

during which the cost of payroll increased from the previous year. Finally, the cost of total 

payroll as a percentage of value of shipments has generally declined since 2000, illustrating a 

reduction in industry non-production or administrative employees, possibly the product of 

selling, general, and administrative (SG&A) cost-cutting measures.

A detailed financial analysis of the manufacturers of each of the product types covered by 

this rulemaking is presented in the manufacturer impact analysis (MIA) (Chapter 12 of this 

TSD). This analysis identifies key financial inputs including cost of capital, working capital, 

depreciation, capital expenditures, etc.

3.2.7 Product Lifetime

The lifetime of residential furnaces, central air conditioners and heat pumps can vary 

greatly 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 central air conditioners and heat pumps. Generally, most 

sources estimate the lifetime of residential furnaces, central air conditioners and heat pumps to 

be in the range of 10 to 20 years. 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 and oil-fired furnaces, unitary air conditioners and heat pumps, based 

on input from appliance experts and many additional sources. Appliance Magazine estimates the 

typical service lifetime range of a gas furnace is 12 to 17 years, while the typical service lifetime 

range of an oil-fired furnace is 15 to 19 years. It also estimates the average lifetime of a gas 

furnace as 15 years and the average lifetime of an oil-fired furnace as 17 years. 42 Similarly, 

Appliance Magazine estimates the average lifetime of a residential central air conditioner as 11 

years and the average lifetime of a residential air-source heat pump as 12 years. AHRI estimates 

the average lifetime of a central air conditioner as 12 to 15 years and the average lifetime of a 

heat pump as 14 years.43
3-29

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

described in detail in chapter 8 of this TSD. Using a combination of RECS data, large-scale 

surveys of commercially available products, and manufacturer information about historical 

shipments and stock, DOE estimated that the median lifetimes of non-weatherized gas furnaces,

mobile home gas furnaces, and non-weatherized oil-fired furnaces are 20.4 years, 16.9 years, and 

26.3 years, respectively. DOE used national survey data along with manufacturer shipment data 

to calculate the distribution of air conditioner and heat pump lifetimes. The mean central air 

conditioner and heat pump lifetimes from the distributions were determined to be 19.0 and 16.2 

years, respectively. Additional information about product lifetimes is contained in chapter 8 (lifecycle cost and payback period analysis) of this TSD.

3.2.8 Market Performance Data

DOE examined the AHRI,44 the CEC,45 and ENERGY STAR46

3.1.1

directories and other 

publicly available data from manufacturers’ catalogs of residential furnaces to develop an 

understanding of the industry and its market. These databases contain information such as 

manufacturer name, model number, input capacity, and efficiency. DOE only examined products 

that meet EPCA’s definition of a residential furnace (see section of this chapter). In 

addition, DOE excluded from its analysis any products that were manufactured for Canada or 

export only and any products in the AHRI Directory of Certified Product Performance that were 

not labeled as “active,” meaning that they are currently being manufactured. For residential 

central air conditioners and heat pumps, DOE examined the AHRI Directory of Certified Product 

Performance to determine the characteristics of residential central air conditioners and heat 

pumps currently available on the market. By definition, residential central air conditioners and 

heat pumps are products with a cooling capacity below 65,000 Btu/h and are aircooled;therefore, DOE did not examine any products that did not meet these criteria. Table 

3.2.21 and Table 3.2.22 show the number of the models in the AHRI Directory of Certified 

Product Performance for each equipment class. As Table 3.2.22 indicates, the large majority of 

residential furnaces are non-weatherized gas furnaces, and there are comparatively few 

weatherized gas, mobile home gas, or oil-fired models. Manufacturers offer very few 

weatherized oil-fired and mobile home oil-fired furnace models. For air conditioners and heat 

pumps, Table 3.2.22 shows that the large majority of these products are split systems, and there 

are relatively few small-duct, high-velocity (SDHV) or space constrained (i.e., through-the-wall) 

models.

Table 3.2.21 Number of Furnace Models Listed in the AHRI Directory of Certified Product 

Performance by Product Class

Product Class Number of Models, as of June 7, 2010

Non-weatherized gas furnaces 5,257

Weatherized gas furnaces 1,847

Mobile home gas furnaces 157

Non-weatherized oil-fired furnaces 1,171

Weatherized oil-fired furnaces 12

Mobile home oil-fired furnaces 18
3-30

Table 3.2.22 Number of Central Air Conditioner and Heat Pump Models Listed in the 

AHRI Directory of Certified Product Performance by Product Class

Product Class Number of Models, as of June 8, 2010

Split system air conditioners 250,966

Split system heat pumps 158,506

Single package air conditioners 2,290

Single package heat pumps 1.436

Small-duct, high-velocity system 732

Space constrained – air conditioners 12

Space constrained – heat pumps 2

3.2.8.1 Efficiency Data

DOE characterized the distribution of furnace efficiencies currently available to 

consumers by dividing the products listed in the DOE database into bins based on their 

efficiency and counting the number of models in each efficiency bin. The efficiency ratings were 

separated into bins in sizes of 1.0 percent or 0.5 percent AFUE, depending on the range of 

efficiencies within each product class. Each bin is named by its upper bound, and each bin’s 

range includes its upper bound but does not include its lower bound (e.g., the 80 percent AFUE 

bin includes all values 79.6 percent AFUE through 80.0 percent AFUE). Figure 3.2.6 though 

Figure 3.2.9 show histograms of the efficiency data for each product class.

Figure 3.2.6 Distribution of Non-Weatherized Gas Furnace Models by AFUE

As Figure 3.2.6 shows, non-weatherized gas furnace efficiencies typically fall into two 

ranges: non-condensing (between 78 percent and 81 percent AFUE) and condensing (at or above 

90 percent AFUE). The vast majority of non-condensing models are at 80 percent AFUE, while 

the largest number of condensing models is at 93 percent AFUE.

0

500

1000

1500

2000

2500

3000

7778798081828384858687888990919293949596979899

100

Number of Basic Models

AFUE (percent)

Nov. 2007 Rule 

Standard
3-31

Figure 3.2.7 Distribution of Weatherized Gas Furnace Models by AFUE

Figure 3.2.7 shows that weatherized gas furnaces have efficiencies ranging from 78 

percent AFUE up to 81 percent AFUE. The highest concentration of models is at 80 percent 

AFUE.

Figure 3.2.8 Distribution of Mobile Home Gas Furnace Models by AFUE

As shown in Figure 3.2.8, the distribution of mobile home gas furnaces is similar to that 

of non-weatherized gas furnaces in that the majority of models fall into one of two ranges – noncondensing (i.e., 78 to 82 percent AFUE) or condensing (i.e., at or above 90 percent AFUE). As 

with non-weatherized gas furnaces, most non-condensing mobile home gas furnaces are 

concentrated at 80 percent AFUE; and most condensing mobile home gas furnaces are at 93 

percent AFUE.

0

100

200

300

400

500

600

700

77.5 78 78.5 79 79.5 80 80.5 81 81.5 82

Number of Basic Models

AFUE (percent)

0

10

20

30

40

50

60

70

80

74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97

Number of Basic Models

AFUE (percent)
3-32

Figure 3.2.9 Distribution of Non-Weatherized Oil-Fired Furnace Models by AFUE

The oil-fired furnace market, illustrated in Figure 3.2.9, is primarily non-condensing, 

while only a few models manufactured in the condensing range (which, for oil-fired furnaces, 

occurs at approximately 88 percent AFUE). The market is concentrated around 83 percent 

AFUE. Very few models are available between 95 and 98 percent AFUE.

DOE conducted a similar analysis of the efficiency of residential central air conditioners 

and heat pumps currently available on the market in AHRI’s Certified Product Performance 

Directory. DOE divided the products into bins based on their efficiency and counted the number 

of models in each efficiency bin. The efficiency ratings were separated into efficiency bins of 

one SEER each, and the SEER ratings are calculated to two decimal points. Figure 3.2.10

through Figure 3.2.14 show histograms of the efficiency data for split system and single package 

central air conditioners and heat pumps, as well as for SDHV systems.

0

50

100

150

200

250

300

7778798081828384858687888990919293949596979899

100

Number of Basic Models

AFUE (percent)
3-33

Figure 3.2.10 SEER Ratings for Single Package Central Air Conditioners in the AHRI 

Certified Product Performance Directory

Figure 3.2.11 SEER Ratings for Single Package Heat Pumps in the AHRI Certified Product 

Performance Directory

1284

651

331

18

0

200

400

600

800

1000

1200

1400

13-13.99 14-14.99 15-15.99 16-16.99

Number of Models

SEER Bin

1417

576

330

25

0

200

400

600

800

1000

1200

1400

1600

13-13.99 14-14.99 15-15.99 16-16.99

Number of Models

SEER Bin
3-34

Figure 3.2.12 SEER Ratings for Split System Central Air Conditioners in the AHRI 

Certified Product Performance Directory

Figure 3.2.13 SEER Ratings for Split System Heat Pumps in the AHRI Directory of 

Certified Product Performance

66942

87908

49975

37736

5181 2182 638 228 89 36 51 8

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

100000

Number of Models

SEER Bin

43820

63704

37782

8793

3300 949 61 73 16

0

10000

20000

30000

40000

50000

60000

70000

Number of Models

SEER Bin
3-35

Figure 3.2.14 SEER Ratings for SDHV Systems in the AHRI Directory of Certified Product 

Performance

Figure 3.2.10 through Figure 3.2.14 show that the SEER Ratings for split system and 

single package air conditioners and heat pumps are mostly concentrated in the 13 to 14.99 SEER 

range, although split systems cover a much higher range of efficiencies. The majority of SDHV 

systems are concentrated in the 11 to 11.99 SEER range. The space constrained products in the 

AHRI Directory of Certified Product Performance all had a SEER rating of 12.0 (12 central air 

conditioners and 2 heat pumps).

For heat pumps, DOE also examined the HSPF ratings of the heat pumps in AHRI’s 

Directory of Certified Product Performance. Figure 3.2.15 through Figure 3.2.17 shows the 

number of single package, split system, and SDHV heat pumps models in the directory that fall 

into the specified HSPF bins.

579

113

38

2

0

100

200

300

400

500

600

700

11-11.99 12-12.99 13-13.99 14-14.99

Number of Models

SEER Bin
3-36

Figure 3.2.15 HSPF Ratings for Single Package Heat Pumps in AHRI’s Directory of 

Certified Product Performance

Figure 3.2.16 HSPF Ratings for Split System Heat Pumps in AHRI’s Directory of Certified 

Product Performance

826

590

9 8

0

100

200

300

400

500

600

700

800

900

7.7-7.99 8-8.49 8.5-8.99 9-9.49

Number of Models

HSPF Bin

24196

60588

44088

20623

4728

478

0

10000

20000

30000

40000

50000

60000

70000

7.7-7.99 8-8.49 8.5-8.99 9-9.49 9.5-9.99 10-10.49

Number of Models

HSPF Bin
3-37

Figure 3.2.17 HSPF Ratings for SDHV Heat Pumps in AHRI’s Directory of Certified 

Product Performance

For single package heat pumps, the HSPF ratings are concentrated in the 7.7 to 8.49 

range. Split system heat pumps cover a greater range of HSPF ratings, and are concentrated in 

the 8 to 8.99 range. For SDHV heat pumps, a significant number of models fall into the range 

between 6.8 and 7.99. Both space-constrained heat pump models listed in AHRI’s directory had 

an HSPF rating of 7.4.

3.2.8.2 Capacity Data

In characterizing the residential furnace market, DOE also examined the distribution of 

models by their input capacity ratings. DOE again divided the products into bins based on their 

input capacities and counted the number of models in each input capacity bin. The capacities 

were separated into bins in sizes of 5,000 Btu/h. Each bin is named by its upper bound, and each 

bin’s range includes its upper bound but does not include its lower bound (e.g., the 80,000 Btu/h 

bin includes all values 75,001 Btu/h through 80,000 Btu/h). Figure 3.2.18 through Figure 3.2.21

show these distributions for each product class covered in this rulemaking.

119

43 43

15

9

0

20

40

60

80

100

120

140

6.8-6.99 7-7.49 7.5-7.99 8-8.49 8.5-8.99

Number of Models

HSPF Bin
3-38

Figure 3.2.18 Distribution of Non-Weatherized Gas Furnace Models by Input Capacity

Figure 3.2.19 Distribution of Weatherized Gas Furnace Models by Input Capacity

0

200

400

600

800

1000

1200

Number of Basic Models

Input Capacity (kBtu/h)

0

50

100

150

200

250

300

Number of Basic Models

Input Capacity (kBtu/h)
3-39

Figure 3.2.20 Distribution of Mobile Home Gas Furnace Models by Input Capacity

Figure 3.2.21 Distribution of Non-Weatherized Oil-Fired Furnace Models by Input 

Capacity

Similarly for air conditioners and heat pumps, DOE divided the products into bins based 

on their cooling capacities and counted the number of models in each cooling capacity bin. The 

capacities were separated into bins in sizes of 6,000 Btu/h (i.e. one half-ton of cooling). Each bin 

is named by its median, and each bin’s range includes its lower bound but does not include its 

upper bound (e.g., the 24,000 Btu/h bin includes all values from 21,001 Btu/h through 27,000 

Btu/h). Figure 3.2.22 and Figure 3.2.23 illustrate these distributions for each product class 

covered in this rulemaking. Split system air conditioners and heat pumps appear to have “sweet 

spots” near the three ton cooling capacity (i.e. 36,000 Btu/h cooling capacity) where a greater 

0

5

10

15

20

25

30

35404550556065707580859095

100105110115120125

More

Number of Basic Models

Input Capacity (kBtu/h)

0

50

100

150

200

250

300

455565758595

105115125135145155165175185195205215225

Number of Basic Models

Input Capacity (kBtu/h)
3-40

range of average efficiencies occurs, as illustrated by Figure 3.2.22 and Figure 3.2.23, while

packaged systems tend to cluster around the three and four ton cooling capacities. 

Figure 3.2.22: Number of Models at Selected Cooling Capacities

Figure 3.2.23: Number of Models at Selected Cooling Capacities

In reviewing the efficiency of residential central air conditioners and heat pumps 

currently available on the market, DOE also examined the relationship between efficiency and 

equipment capacity. Figure 3.2.24 through Figure 3.2.27 show the average SEER ratings at 

increment of half tons of cooling available for single package and split system air conditioners 

and heat pumps in AHRI’s Directory of Certified Product Performance.

0

10000

20000

30000

40000

50000

60000

24,000 30,000 36,000 42,000 48,000 54,000 60,000

Number of Models

Cooling Capacity (Btu/hr)

Split AC

Split HP 

0

100

200

300

400

500

600

24,000 30,000 36,000 42,000 48,000 54,000 60,000

Number of Models 

Cooling Capacity (Btu/hr)

Packaged AC

Packaged HP
3-41

Figure 3.2.24 Average SEER Ratings at Incremental Cooling Capacities for Single Package 

Air Conditioners in AHRI’s Directory of Certified Product Performance

Figure 3.2.25 Average SEER Ratings at Incremental Cooling Capacities for Split System 

Air Conditioners in AHRI’s Directory of Certified Product Performance

12.5

13

13.5

14

14.5

15

15.5

16

16.5

17

SEER

Cooling Capacity (Btu/hr)

pkg AC max

pkg AC avg

pkg AC min

12.5

14.5

16.5

18.5

20.5

22.5

24.5

SEER

Cooling Capacity (Btu/hr)

split AC max

split AC avg

split AC min
3-42

Figure 3.2.26 Average SEER Rating at Incremental Cooling Capacities for Single Package 

Heat Pumps in the AHRI Directory of Certified Product Performance

Figure 3.2.27 Average SEER Rating at Incremental Cooling Capacities for Split System 

Heat Pumps in the AHRI Directory of Certified Product Performance

The average SEER ratings for single package air conditioners and heat pumps are 

concentrated generally in the 13 to 15 SEER range for the entire range of cooling capacities. 

Split system air conditioners and heat pumps display a greater range of average SEER ratings at 

lower cooling capacities, and then appear to become concentrated between 13 and 15 SEER at 

the higher cooling capacities. Split system air conditioners and heat pumps appear to have “sweet 

spots” near the three ton cooling capacity (i.e., 36,000 Btu/h cooling capacity) where a greater 

range of average efficiencies occurs, and where the highest average SEER ratings occur. 

12.5

13

13.5

14

14.5

15

15.5

16

16.5

17

SEER

Cooling Capacity (Btu/hr)

pkg HP max

pkg HP avg

pkg HP min

12.5

14.5

16.5

18.5

20.5

22.5

SEER

Cooling Capacity (Btu/hr)

split HP max

split HP avg

split HP min
3-43

Figure 3.2.28: Number of Models at Selected Cooling Capacities

DOE also examined the average HSPF ratings at each equipment capacity for heat pumps 

listed in AHRI’s Directory of Certified Product Performance. Figure 3.2.29 and Figure 3.2.30

illustrate the average HSPF at each available capacity rating in AHRI’s directory for single 

package and split system. The HSPF ratings for single package heat pumps are consistently 

between 7.7 and 8.2 HSPF for the entire range of cooling capacities. Split system heat pumps 

appear to have a greater range of average HSPF ratings at lower cooling capacities, and a smaller 

range of average HSPF ratings at higher cooling capacities. The average HSPF ratings peak near 

3 tons (36,000 Btu/h) and 4 tons (48,000 Btu/h). 

Figure 3.2.29 Average HSPF at Incremental Cooling Capacities for Single Package Heat 

Pumps in the AHRI Directory of Certified Product Performance

0

10000

20000

30000

40000

50000

60000

24,000 30,000 36,000 42,000 48,000 54,000 60,000

Number of Models

Cooling Capacity (Btu/hr)

Split AC

Split HP 

7.5

7.7

7.9

8.1

8.3

8.5

8.7

8.9

9.1

HSPF

Cooling Capacity (Btu/hr)

pkg HP max

pkg HP avg

pkg HP min
3-44

Figure 3.2.30 Average HSPF Rating at Incremental Cooling Capacities for Split System 

Heat Pumps in the AHRI Directory of Certified Product Performance

The HSPF ratings for single package heat pumps are consistently between 7.7 and 8.2 

HSPF for the entire range of cooling capacities. Split system heat pumps appear to have a greater 

range of average HSPF ratings at lower cooling capacities, and a smaller range of average HSPF 

ratings at higher cooling capacities. The average HSPF ratings peak near 3 tons (36,000 Btu/h) 

and 5 tons (60,000 Btu/h). The average HSPF ratings of SDHV heat pumps are between 6.8 and 

8 for the entire range of capacities.

Lastly, DOE investigated the relationship between EER and equipment capacity. Figure 

3.2.31 through Figure 3.2.34 contain plots of EER compared to equipment capacity in half ton 

increments for the conventional product classes. The maximum EER values for packaged 

systems suggest that units are optimized around 2, 3, and 4 tons of cooling, but average values do 

not necessarily reflect this trend. Plots of this data for split systems did not contain the same 

peaks and suggest that the optimization of EER for certain tonnages is not as important as other 

factors.

7.5

8

8.5

9

9.5

10

10.5

11

HSPF

Cooling Capacity (Btu/hr)

split HP max

split HP avg

split HP min
3-45

Figure 3.2.31 Average EER Ratings at Incremental Cooling Capacities for Single Package 

Air Conditioners in AHRI’s Directory of Certified Product Performance

Figure 3.2.32 Average EER Ratings at Incremental Cooling Capacities for Split System Air 

Conditioners in AHRI’s Directory of Certified Product Performance

9.5

10

10.5

11

11.5

12

12.5

13

13.5

EER

Cooling Capacity (Btu/hr)

pkg AC max

pkg AC avg

pkg AC min

9.00

10.00

11.00

12.00

13.00

14.00

15.00

16.00

EER

Cooling Capacity (Btu/hr)

split AC max

split AC avg

split AC min
3-46

Figure 3.2.33 Average EER Rating at Incremental Cooling Capacities for Single Package 

Heat Pumps in the AHRI Directory of Certified Product Performance

Figure 3.2.34 Average EER Rating at Incremental Cooling Capacities for Split System 

Heat Pumps in the AHRI Directory of Certified Product Performance

3.2.9 Historical Shipments and Efficiencies

3.2.9.1 Historical Shipments 

Information about annual furnace shipment trends allows DOE to estimate the impacts of 

energy conservation standards on the residential furnace industry. DOE has examined unit 

shipments and value of shipments using publicly available data from the U.S. Census Bureau’s 

9.5

10

10.5

11

11.5

12

12.5

13

EER

Cooling Capacity (Btu/hr)

pkg HP max

pkg HP avg

pkg HP min

8.5

9.5

10.5

11.5

12.5

13.5

14.5

15.5

EER

Cooling Capacity (Btu/hr)

split HP max

split HP avg

split HP min
3-47

Annual Survey of Manufacturers (ASM) and Current Industrial Reports (CIR) and estimates 

from AHRI and Appliance Magazine.

Appliance Magazine provides an estimate of annual unit shipments for various 

appliances, including warm-air gas and oil-fired furnaces. The data, however, does not 

distinguish between shipments for new construction and replacement. Figure 3.2.35 presents 

annual shipments of gas and oil-fired residential furnaces (excluding exports) from 2000 to 2009 

based on Appliance Magazine estimates.47

From the data, it is apparent that gas furnaces comprise the vast majority of the 

residential furnace industry. Shipments of gas furnaces grew steadily until 2005, then plunged in 

the subsequent four years to 30 percent below the unit shipments at the beginning of the decade. 

This trend mirrors that of new housing starts, revealing that gas furnace shipments are driven by 

the new construction market. In contrast, shipments of oil-fired furnaces remained relatively 

steady over the first part of the decade, before dropping by more than half between 2005 and 

2009. This directly corresponds with rising heating oil prices, shown in Figure 3.2.36, which 

more than doubled in the same period. This strong correlation between shipments and fuel prices 

indicates that the oil warm-air heating market is driven in large part by replacements.

Figure 3.2.35 Residential Furnace Industry Shipments (Domestic and Imported)48

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

3,500,000

4,000,000

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Oil-Fired Units Shipped

Gas Units Shipped

Year

Gas Furnaces

Oil-Fired Furnaces
3-48

Figure 3.2.36 Average Fuel Prices, 2000 to 200949,50,51

For central air conditioners and heat pumps, AHRI provided historical shipments data 

over the 1990-2009 time-period disaggregated into the four primary product classes.52 

Historical shipments from 1972-1989 were also provided by AHRI from previous data submittals 

to the Lawrence Berkeley National Laboratory (LBNL).53

Table 3.2.23

 The data for 1972-1989 included 

some shipments of 3-phase as well as single-phase central air conditioners and heat pumps, 

whereas the data for 1990-2009 included only single-phase central air conditioners. DOE 

disaggregated the shipments for single-phase and 3-phase central air conditioner and heat pump 

equipment in the earlier data and included only single phase units. summarizes the 

historical shipments data. 

$0

$5

$10

$15

$20

$25

$30

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Delivered Fuel Price ($/MMBtu)

No. 2 Heating Oil

Natural Gas
3-49

Table 3.2.23 Central Air Conditioner and Heat Pump Shipments

Year Split CAC Single Package 

CAC Split HP Single Package HP

thousands thousands thousands thousands

1972 1,489 257 28 52

1973 1,742 318 35 52

1974 1,503 289 49 48

1975 888 159 83 45

1976 1,219 231 177 74

1977 1,364 218 329 89

1978 1,546 253 389 97

1979 1,428 248 376 107

1980 1,233 134 293 61

1981 1,293 122 348 66

1982 1,037 111 267 49

1983 1,558 192 455 82

1984 1,857 189 535 98

1985 1,784 203 619 107

1986 1,876 203 680 106

1987 2,204 237 714 103

1988 2,334 247 649 91

1989 2,516 267 650 91

1990 2,241 334 643 104

1991 2,388 306 615 96

1992 2,254 330 647 101

1993 2,474 346 718 107

1994 3,087 387 825 118

1995 3,221 384 834 120

1996 3,635 418 936 139

1997 3,364 395 917 142

1998 4,010 406 1,019 148

1999 4,317 429 1,044 147

2000 4,280 437 1,073 159

2001 3,931 361 1,180 165

2002 4,381 380 1,229 165

2003 4,281 390 1,350 174

2004 4,561 414 1,584 190

2005 5,461 455 1,810 213

2006 4,038 330 1,807 190

2007 3,582 338 1,570 199

2008 3.171 274 1,566 189

2009 2,887 234 1,389 162

Source: Air-Conditioning, Heating, and Refrigeration Institute (AHRI)
3-50

3.2.9.2 Value of Shipments

Table 3.2.24 and Table 3.2.25 provide the value of shipments for the residential furnace 

and residential central air conditioner and heat pump industries from 2005 to 2009 using the U.S. 

Census Bureau CIRs.54

Table 3.2.24 Value of Residential Furnace Shipments by Year

The CIR expresses all dollar values in current dollars (e.g., 2005 data are 

expressed in 2005$). Using the gross domestic product (GDP) deflator, DOE converted each 

year’s shipment values to 2009$; 2009 was the last year included in the CIR data set.

55

Year

Value of Shipments

$, millions

Value of Shipments in 2009$

$, millions

2009 1,916 1,916

2008 1,826 1,863

2007 2,090 2,173

2006 2,205 2,331

2005 2,268 2,434

Table 3.2.25 Value of Residential Central Air Conditioner and Heat Pump Shipments by 

Year56

Air Conditioners Heat Pumps

Year

Value of 

Shipments

$, millions

Value of Shipments 

in 2009$

$, millions

Value of 

Shipments

$, millions

Value of Shipments 

in 2009$

$, millions

2009 6,247 6,247 2,191 2,191

2008 6,994 7,136 2,000 2,041

2007 7,603 7,905 2,030 2,111

2006 7,402 7,825 1,987 2,101

2005 6,979 7,490 1,869 2,006

From these data it is apparent that the residential furnace industry has gradually been 

shrinking in proportion to new housing starts since 2005. The residential central air conditioner 

portion of the central air conditioner and heat pump industry has been shrinking since 2007, but

the heat pump industry has increased slightly. 

3.2.9.3 Historical Efficiencies of Central Air Conditioners and Heat Pumps

AHRI provided historical shipment-weighted efficiency data (SWEF) data spanning the 

years 1992 to 2009.

28 Between1992, the year in which the first set of standards for central air 
3-51

conditioners and heat pumps became effective; and 2006, when an updated set of standards 

became effective, the SWEFs for central air conditioners grew by approximately one SEER 

point. Figure 3.2.37 shows the SWEFs for split system and single package central air 

conditioners. For 1992-2005 and 2007 to 2009, linear fits provide a good estimate of the SWEF 

growth rate. The updated standards caused a jump in SWEF for 2006 and 2007, but by 2008 the 

SWEF growth rate returned to a level slightly above the SWEF growth from 1992 to 2005.

However, the SWEF growth rate for packaged air conditioners remained significantly higher 

than the split-system SWEF for 2007 to 2009. Table 3.2.26 provides a summary of the SWEF 

growth rates for each product class. 

Figure 3.2.37 Central Air Conditioner Historical Shipment-Weighted Efficiencieso

Table 3.2.26 Central Air Conditioner Shipment-Weighted Efficiency Growth Rates

SWEF Growth Rate

(SEER increase per year)

Product Class 1992-2005 2007-2009

Split system air conditioners 0.0703 0.0900

Single package air conditioners 0.0778 0.2900

For heat pumps shipped between 1992 and 2006, the SEER-based also grew by 

approximately one SEER point. Figure 3.2.38 shows the SEER-based SWEFs for split system 

and single package heat pumps. . Table 3.2.27 provides a summary of the SEER-based SWEF 

growth rates for each product class. The growth rates for both split and packaged systems were 

 o Source: Air-Conditioning, Heating, and Refrigeration Institute (AHRI).

10.00

10.50

11.00

11.50

12.00

12.50

13.00

13.50

14.00

1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

Shipment Weighted SEER

Year

Split AC

Package AC
3-52

much higher for 2007 to 2009, as compared to the rest of the timeline. Similar to air conditioners, 

the packaged heat pumps exhibited a higher SWEF growth rate than the split systems. AHRI did 

not provide historical SWEF data for heat pump HSPFs.

Figure 3.2.38 Heat Pump Historical Shipment-Weighted Efficiencies base on SEERp

Table 3.2.27 Heat Pump Shipment-Weighted Efficiency Growth Rates

SWEF Growth Rate

SEER increase per year

Product Class 1992-2005 2007-2009

Split system heat pumps 0.0739 0.1950

Single package heat pumps 0.0736 0.2850

3.2.10 Saturations in U.S. Households

Stock saturation refers to the percentage of the housing stock equipped with a given

product or exhibiting a certain feature. As of 2005, 46.4 percent (51.6 million) of homes in the 

United States have central warm-air furnaces.57 Of these furnaces, 44.7 million are gas furnaces, 

2.8 million are oil-fired furnaces, and 4.1 million are liquid petroleum gas (LPG) furnaces. Site 

energy consumption attributable to residential warm-air space heating is 46.0% (5.37 quads) of 

total U.S. energy consumption.58 Within individual homes, warm-air space heating represents, on 

average, 42.7% percent (40.5 million Btu) of total annual household energy consumption.59

 p Source: Air-Conditioning, Heating, and Refrigeration Institute (AHRI)

The 

10.00

10.50

11.00

11.50

12.00

12.50

13.00

13.50

14.00

14.50

1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010

Shipment Weighted SEER

Year

Split HP

Package HP
3-53

American Housing Survey (AHS) provides historical stock saturations for central air

conditioning and heat pump equipment for every other year between 1991−2007. 60 Table 3.2.28

summarizes the saturations for central air conditioners, heat pump, and both types of equipment. 

Central air conditioners and heat pump saturation has grown from 38.6 percent to 64.6 percent 

from 1991 to 2007.

Table 3.2.28 Central Air Conditioner Heat Pump Historical Housing Stock Saturations

Year CAC HP Total

1991 30.8% 7.8% 38.6%

1993 32.0% 8.5% 40.5%

1995 33.9% 9.1% 43.0%

1997 36.3% 12.0% 48.3%

1999 41.4% 11.4% 52.8%

2001 45.0% 11.3% 56.3%

2003 46.5% 11.7% 58.2%

2005 50.2% 12.7% 62.9%

2007 51.8% 12.8% 64.6%

3.3 FURNACE TECHNOLOGY ASSESSMENT

The purpose of the technology assessment is to develop a list of technology options that 

manufacturers can use to improve the efficiency of residential furnaces. The following 

assessment provides descriptions of those technology options that apply to all product classes.

In preparation for the screening and engineering analyses, DOE identified several 

possible technology options and examined the most common efficiency-improving technologies 

used today. These technology options provide insight into the technological improvements 

typically used to increase the energy efficiency of residential furnaces.

3.3.1 Furnace Characterization

At a basic level, furnaces are characterized based on their whether they are weatherized, 

whether they are designed for condensing operation, and the physical configuration of the heat 

exchanger and blower.

3.3.1.1 Weatherization

Residential furnaces can be described as either weatherized or non-weatherized 

furnaces. Weatherized furnaces are generally installed outdoors (often on rooftops), and nonweatherized furnaces are installed indoors. The main difference between a weatherized furnace 

and a non-weatherized furnace is that the weatherized furnace has a weather-resistant external 

case, while the non-weatherized furnace does not. Weatherized furnaces are only used as part 

of unitary heating and cooling units, which means that an air conditioner is contained in the 

same package. DOE does not know of any manufacturer that presently sells a stand-alone 

furnace approved for outdoor installation. Manufacturers produce very few weatherized oilfired furnaces. 
3-54

Because weatherized furnaces are subject to adverse weather conditions, the heat loss 

through the jacket of a weatherized furnace is higher than that of a non-weatherized furnace. 

To account for this, the DOE test procedure requires manufacturers to rate weatherized 

furnaces for outdoor installation; they do so by applying a higher multiplication factor to the 

jacket losses in order to simulate outdoor conditions. 

The DOE test procedure specifies that all non-weatherized furnaces shall be rated and 

tested as isolated combustion systems (ICS), which means that the furnace is isolated from the 

heated space and draws combustion and dilution air, if applicable, from the outdoors. Because all 

non-weatherized furnaces are rated under the same conditions, those that are installed in the 

heated space do not have a rated AFUE advantage over those that are installed outside of the 

heated space, such as non-weatherized furnaces installed in garages, due to their jacket losses. 

However, in real-world applications, conductive heat transfer through the jacket of a nonweatherized furnace installed in the heated space will dissipate as useful heat to the heated space. 

This means that non-weatherized furnaces installed in the heated space may be able to realize 

higher operational efficiencies as compared with their ratings.

3.3.1.2 Condensing Operation

Non-weatherized furnaces can be either non-condensing or condensing. When the flue 

gas temperature is substantially higher than the water vapor dew point and the latent heat (the 

heat from condensation of water vapor in the combustion products) is not recovered in the 

appliance's heat exchanger, the furnace is classified as non-condensing. The annual fuel 

utilization efficiency (AFUE) of such furnaces is generally below 82 percent AFUE for natural 

gas furnaces and 88 percent AFUE for oil-fired furnaces. Condensing furnaces recover more 

heat from the combustion products by condensing the water vapor in the flue gases. There are 

no condensing weatherized furnaces available on the furnace market primarily because of 

concerns that the condensate could freeze and damage the furnace. 

As water vapor begins to condense in the furnace's heat exchanger, the latent heat 

recovered from the vapor raises the furnace's AFUE to above 90 percent, with a higher AFUE 

indicating a greater amount of condensation being formed. Condensing furnaces typically require 

additional components, such as a corrosion-resistant secondary heat exchanger and a condensate 

drain device. Condensing furnaces also cannot use a natural draft venting system, since the 

buoyancy of the cooler flue gases is not sufficient to draw the gases up a regular chimney. 

Forced and induced draft blowers are used in conjunction with condensing furnaces to draw air 

into the combustion zone and exhaust the flue gases through the vents. 

Furnaces generally are not manufactured in the 82 to 89 percent AFUE range. In this 

range, corrosive condensate can form in the vent system under certain operating conditions, 

which can cause safety concerns in venting systems used for non-condensing furnaces (i.e., 

Category I and Category III venting). However, the temperature of the flue gases is still too high 

at these efficiencies to allow for the use of polyvinylchloride (PVC) for the venting system. 

Proper venting of such a furnace requires a special stainless steel venting system, which is often 

cost prohibitive. As a result, manufacturers typically do not offer products in this range of 

efficiencies.
3-55

3.3.1.3 Configurations

Three different airflow configurations are commonly used in residential furnaces: 1) 

horizontal; 2) upflow; and 3) downflow or counterflow. A fourth design, called multipoise or 

multiple direction, allows the furnaces to be set up in two or three of the previously listed 

configurations depending on the installation requirements. Each configuration requires a 

different arrangement of the furnace’s basic components. 

The horizontal furnace configuration is commonly used in attics, crawl spaces, and other 

locations where the height of the furnace is the constraining dimension. Air enters at one end of 

the unit through the blower compartment, is forced horizontally over the heat exchanger, and 

then exits the furnace at the opposite end through installed ductwork that distributes it to the 

heated space. Horizontal furnaces are most common in weatherized (especially rooftop) units.

The upflow “highboy” configuration is most commonly used for basement or first-floor 

equipment room installations where floor space is at a premium. In this configuration, the blower 

is located below the heat exchanger. Air enters at the bottom or lower side of the unit and leaves 

at the top through a warm-air outlet (plenum). The upflow “lowboy” furnace configuration

occupies more floor space and is lower in height than the upflow highboy design, which makes it 

suited for basement installations where both floor space and height are constraints. In the upflow 

lowboy configuration, manufacturers place the blower alongside the heat exchanger. A return-air 

plenum is installed above the blower compartment, and a supply-air plenum is installed above 

the heat exchanger compartment. Upflow highboy configuration is most common in nonweatherized gas and oil-fired furnaces.

The downflow, or counterflow, configuration is used in houses that have an under-thefloor type of heat distribution system, where the ductwork that delivers heated air is located 

beneath the conditioned space. In this configuration, the blower assembly is located above the 

heat exchanger, and the return-air plenum is connected to the top of the unit. Most mobile home 

furnaces are installed in the downflow configuration.

The multipoise, or multiple-direction, furnace design allows for the unit to be 

configured as upflow, horizontal, or downflow, depending on the requirements of the particular

installation. Some multipoise furnaces are able to be configured in all three configurations (i.e., 

upflow, horizontal, and downflow), while others are only designed to be set up in two of the 

three configurations (e.g., upflow and horizontal). Demand is growing for these products 

because they allow for more flexibility and can accommodate different types of installations. 

Multipoise appliances are more expensive to manufacture because they require extensive 

testing and more complicated controls. The majority of modern non-weatherized furnaces are 

multipoise. 

Shipments data from AHRI show that multipoise furnaces account for approximately 

two-thirds of total shipments. Upflow designs account for 25 percent, and downflow and 

horizontal designs together account for just 9 percent.
3-56

3.3.2 Baseline Product Components and Operation

A basic residential gas furnace comprises a hot surface or direct spark ignition system, 

tubular inshot burners, non-condensing heat exchanger, single-speed air blower assembly with 

PSC motor and forward swept blades, single-speed mechanical draft combustion fan assembly, 

and automatic controls. A basic residential oil furnace comprises an interrupted spark ignition 

system, flame retention power burner, non-condensing heat exchanger, and a single-speed air 

blower assembly.

3.3.2.1 Heat Exchanger 

The heat exchanger’s function is to transfer heat from the combustion gases to the 

circulating air, which is then distributed to the heated space. The heat exchanger of a baseline 

unit is usually constructed from aluminized, cold-rolled steel or stainless steel with welded or 

crimped seams. There are two types of primary heat exchangers commonly used in residential 

furnaces: individual-section and drum. 

Individual-section heat exchangers consist of a number of separate heat exchanger

sections. Each section has an individual fuel-burning device. The sections are typically joined 

together at the upstream end of the heat exchanger so that a common ignition device can light all 

of the burners. The sections are also joined together at the downstream end to direct flue gases to 

a common flue. The individual-section type of heat exchanger is used primarily in gas-burning 

products. 

Tubular and clamshell heat exchangers are different types of the individual-section heat 

exchanger. A tubular heat exchanger comprises several metal tubes bent in shape, while the 

clamshell, or serpentine, heat exchanger is manufactured by folding specially-formed sheets of 

thin metal. Heat exchanger designs differ from manufacturer to manufacturer, but are typically 

similar across all product lines for a specific manufacturer. Tubular heat exchangers require a 

smaller initial investment than clamshell types, but can be more costly if produced in high 

volume. 

Drum heat exchangers have a single combustion chamber and use a single-port fuelburning device. The drum heat exchanger is used primarily in oil-firing units and occasionally in 

mobile home gas furnace designs. All oil-fired units use drum heat exchangers. 

3.3.2.2 Burner Assembly 

Gas Burners. The gas burner assembly in a residential furnace functions to: (1) control 

and regulate the flow of gas, (2) ensure the proper mixture of gas with air, and (3) ignite the gas 

under safe conditions. To accomplish these functions, a gas burner assembly consists of four 

major parts or sections: a gas valve, an ignition device, a manifold and orifice(s), and gas burners 

and adjustments. 

The gas valve consists of a number of parts—a hand shutoff valve, a pressure-reducing 

valve, safety shutoff equipment, and an operator-controlled automatic gas valve—each 

performing a different function. In modern units, these parts are all contained in a combination 

gas valve (CGV). 
3-57

The manifold connects the gas supply from the gas valve to the burners and delivers gas 

in equal proportions to each burner. The orifices permit a high-velocity stream of gas to enter 

the burners and meter the gas flow. 

Gas-burning devices require the correct mixture of air (i.e., oxygen) and gas to be 

supplied to ensure complete combustion. Primary air, which is mixed with the gas prior to 

combustion, accounts for 30 to 50 percent of the total air required for stoichiometric combustion. 

Secondary air, which is supplied to the flame at the time of combustion, provides the remaining 

50 to 70 percent of the total air supply to prevent the formation of noxious carbon monoxide. To 

produce efficient and safe combustion, it is essential to maintain the proper ratio of primary to

secondary air. In gas furnaces, the burners are typically “inshot” (i.e., single-port), which means

that one long flame is directed into the heat exchanger section after ignition. The fuel enters the 

burner through a venturi tube that accelerates the gas stream. In turn, the high velocity of the gas 

stream creates a suction effect that entrains the primary air into the tube and mixes it with gas

from the gas service line. This mixture of gas and primary air oxidizes in the first stage of 

combustion. In the second stage of combustion, secondary air is introduced to the combustion 

zone in excess to burn the remaining gas. 

Oil Burners. In an oil-fired furnace, the oil burner is typically a flame retention head 

burner, also known in the industry as a high-pressure, atomizing burner. This burner forces oil at 

a pressure of 100 pounds per square inch gauge (psig) through the nozzle, breaking the oil into 

fine, mist-like droplets. Some models require operating oil pump pressures in the 140 to 200 psig 

range. Vanes supply combustion air to a low-pressure area created by the atomized oil spray. 

These supply vanes create turbulence and facilitate mixing of the air and fuel. 

The main components of a high-pressure, atomizing burner are the power assembly (fuel 

pumps, motor, fan, and air shutters) and the nozzle assembly. All high-pressure burners have 

electronic ignition. A step-up transformer supplies the power to two electrodes, which causes a 

spark to jump. The force of the air in the blast tube causes the spark to arc into the oil-air 

mixture, thereby igniting it. 

3.3.2.3 Electronic Ignition 

Modern furnaces 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 (which house electronic 

circuitry required to control the ignition system) operate only during the active mode. The 

different types of electronic ignition systems are discussed in greater detail below. 

Hot Surface Ignition (HSI). Hot surface ignition (HSI) is the most common form of 

electronic ignition in gas furnaces and the baseline ignition component for non-weatherized gas 

furnaces and mobile home gas furnaces. The igniter in this system is an electrically heated 

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

Hot surface igniters use simpler controls and are regarded in the industry as being more reliable 

than other types of electronic ignition. In HSI operation, a voltage is applied to the igniter until 

its surface is sufficiently hot to light the system’s main burner directly. Silicon nitride igniters 
3-58

offer a durability advantage over silicon carbide, and as a result they have largely replaced 

silicon carbide igniters in most modern furnaces.61

Direct Spark Ignition (DSI). This type of ignition system provides the same functionality 

as a hot surface igniter: it serves to ignite the main burner and acts as a flame sensor. As its name 

implies, the DSI lights the main burner directly by generating a spark. There is no pilot light. 

Flame rectification is used to detect flame presence: if a flame is present, the control module will 

hold the gas valve open and cut off power to the igniter. If a flame has not been established 

within the trial-for-ignition period (approximately 4 to 7 seconds), the system will go into 

lockout and must be reset. Direct spark igniters are the baseline ignition component for 

weatherized gas furnaces, which DOE is not analyzing in this rulemaking, as discussed in section 

III.G.2.a of the final rule.

Intermittent Pilot Ignition. This is a device that lights a pilot by generating a spark. The 

pilot light in turn lights the main burner. DOE could not identify any intermittent pilot ignition 

systems that have been incorporated into today’s furnace designs.

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 force of the air in the blast tube causes the spark to arc into 

the oil-air mixture, thereby igniting it. 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 trial-forignition (TFI) period. 

3.3.2.4 Mechanical Draft

Modern furnaces in all product classes employ mechanical draft, in which motorized fans

to supply and regulate air for combustion and create sufficient draft to exhaust the flue gases. 

The fan is typically driven by a single-speed, two-speed, or variable-speed motor in the 75 to 90 

watt range. 62

Mechanical draft systems can be designed as either induced draft (i.e., power vent) or 

forced draft (i.e., power burner of power combustion) systems. An induced draft fan is located 

downstream of the heat exchanger in the venting system 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 products of 

combustion through the vent system. Both methods improve efficiency over natural draft 

systems by providing the correct fuel-to-air ratio to optimize combustion efficiency and by 

regulating draft to optimize heat transfer in the heat exchanger.

Induced draft combustions systems also have a safety benefit as compared with forced 

and natural draft systems. Because airflow through the vents is created by inducing a negative 

pressure in the heat exchanger, air is pulled through the furnace. This suction mechanism ensures 

that carbon monoxide and other toxic flue gases cannot leak into the heated space in the case of a 

cracked heat exchanger or venting system. 
3-59

Induced draft is a baseline feature of non-weatherized gas furnaces and weatherized gas 

furnaces. Forced draft is a baseline feature of mobile home gas furnaces and non-weatherized 

oil-fired furnaces.

3.3.2.5 Blower Assembly

The circulating air blower of a residential furnace is typically a centrifugal fan-impeller 

with a shaft-mounted motor. The assembly with the fan shroud is mounted in an enclosure at the 

base of an upflow furnace, the return-air end of a horizontal unit, or the top of a downflow 

furnace. 

Air blowers in residential furnaces generally use multi-speed induction motors, typically 

permanent split capacitor (PSC) designs. Furnaces with premium components may offer 

electronically commutated (brushless permanent magnet) motors (ECM),

q

The blower motor is typically sized for a residential HVAC system based on the quantity 

of air being moved and the resistance of the system. Because the airflow requirements of central 

air conditioners are typically higher than those of furnaces, the requirements of the air 

conditioning system frequently determine the size and electricity consumption of the blower fan 

motor. However, energy consumed by the blower is not accounted for by the AFUE calculation. 

DOE is evaluating energy conservation standards for furnace fan electricity consumption in a 

separate rulemaking procedure.

which have a higher 

efficiency and other features, such as modulating capacity controlled by the thermostat. 

r

3.3.2.6 Installation and Venting Options

Non-weatherized furnaces installed within the structure that do not communicate with the 

heated space (e.g., in a garage, utility closet, or basement) are considered “isolated combustion 

systems,” or ICS. Heat conduction through the furnace jacket dissipates to the unconditioned air 

around the furnace and is wasted. ICS is the baseline installation for rating and testing of all nonweatherized furnaces, per DOE’s test procedure.

The DOE test procedure specifies that all weatherized furnaces shall be rated and tested 

as outdoor installations. Weatherized furnaces contain an integral venting system that intakes 

combustion air and exhausts products of combustion to the outside air. Because the combustion 

system has no communication with the heated space, there are no off-cycle or infiltration losses. 

The jacket loss from a weatherized furnace, however, is significantly higher than that from an 

ICS because the unit is exposed to inclement weather such as wind, rain, and snow.

3.3.3 Technology Options That Improve AFUE

DOE identified the following technology options as having the potential to improve the 

efficiency of furnaces: 

 q ECM is a trademark of General Electric Company. It is a commonly used industry term; therefore, DOE will use 

this acronym hereinafter to refer to brushless permanent magnet motors. r See DOE’s residential furnace fan webpage for more information, available at 

www.eere.energy.gov/buildings/appliance_standards/residential/furnace_fans.html
3-60

1. Condensing Secondary Heat Exchanger for Non-Weatherized Furnaces

2. Heat Exchanger Improvements for Non-Weatherized Furnaces

3. Condensing and Near-Condensing Technologies for Weatherized Gas Furnaces

4. Two-Stage and Modulating Combustion

5. Pulse Combustion

6. Low NOx Premix Burners

7. Burner derating

8. Insulation Improvements

9. Off-Cycle Dampers

10. Concentric Venting

11. Low-Pressure, Air-Atomized Oil Burner

12. High-Static Oil Burner

13. Delayed-Action Oil Pump Solenoid Valve

DOE considered these technology options further in the screening analysis.

3.3.3.1 Condensing Secondary Heat Exchanger for Non-Weatherized Furnaces

The energy efficiency of gas and oil-fired furnaces can be improved by increasing the 

fraction of heat extracted from the combustion gases such that the water vapor begins to 

condense. Condensation of the vapor in the flue gases signals an efficient transfer of energy from 

combustion gases to circulation air and is usually achieved by the addition of a secondary heat 

exchanger. The secondary heat exchanger, which is typically a tube-fin type heat exchanger 

constructed from corrosion-resistant stainless steel, allows more heat to be extracted from the 

flue gases before the products of combustion exit through the flue to the vent system. 

Flue gas condensate is acidic and corrosive. Corrosion due to condensation of 

combustion gases limits the AFUE that can be achieved by a non-condensing furnace to ratings 

below 82 percent AFUE. Using corrosion-resistant heat exchangers and lining the vent system 

with corrosion-resistant material allows for AFUE improvements while reducing the risk of 

corrosion damage to the heat exchanger and venting system. 

3.3.3.2 Heat Exchanger Improvements for Non-Weatherized Furnaces

Improving the heat exchanger for furnaces can increase the rate of heat transfer from the 

hot combustion gases to the circulation air that is distributed to the heated space. The improved 

heat transfer increases thermal efficiency and AFUE.

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

standard furnaces to incorporate any combination of (1) increased heat exchanger surface area, 

(2) heat exchanger surface features, and (3) heat exchanger baffles and turbulators.

Increased Heat Exchanger Surface Area. The performance of the heat exchanger can be 

improved by increasing surface area. 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 

furnace, thereby improving the furnace’s ability to efficiently extract heat from the hot 

combustion gases. The result is an increase in the steady-state efficiency of the unit, and thus, the 

AFUE. 
3-61

Generally, manufacturers increase the surface area of the heat exchanger by increasing 

the size of the secondary heat exchanger. If the gas temperature is too low, the gases will begin 

to condense inside the primary heat exchanger, which is usually not corrosion-resistant. Areas 

where condensation occurs in the primary heat exchanger are known in the industry as “cold 

spots” and are detrimental to the integrity of the heat exchanger. Manufacturers thus limit the 

surface area of the primary heat exchanger in order to avoid the formation of cold spots and 

instead increase surface area in the corrosion-resistant secondary heat exchanger. 

Heat Exchanger 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 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 heat transfer through the walls of the 

heat exchanger. Turbulators, which are common in gas furnaces, are typically very thin, twisted 

strips of stainless steel inserted longitudinally into the tubes of the secondary heat exchanger, 

parallel to air flow. They improve heat transfer by restricting flow in the heat exchanger tubes, 

increasing turbulence in the combustion gases. Baffles, frequently used in oil-fired furnaces, are 

simply fins or extrusions from the combustion-air side of the heat exchanger wall. Baffles 

enhance heat transfer primarily by deflecting the products of combustion toward the heat 

exchanger wall. 

3.3.3.3 Condensing and Near-Condensing Technologies for Weatherized Gas Furnaces

In weatherized furnaces, which are installed outdoors and therefore exposed to winter 

weather conditions, the liquid condensate could freeze in the drain and disrupt proper operation. 

Manufacturers have not succeeded in developing a weatherized furnace that can prevent 

condensate from freezing. 

3.3.3.4 Two-Stage and Modulating Combustion

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

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

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

heating load. This improves comfort by reducing large fluctuations in room temperature. 

Because burner on-time increases, however, fuel use does not decrease; and with combustion air 

supply held constant, there is minimal effect on AFUE.63

Two-Stage and Modulating Gas Burners. Two-stage and modulating gas burners reduce 

cycling of the furnace by reducing the flow rate of gas at lower heating loads. These burners 

regulate gas flow but not airflow. When a modulating or two-stage burner is paired with a single-

 When the combustion air supply is 

modulated to match the fuel input rate, however, the burner is essentially derated, making the 

heat exchanger more effective during periods of lower heat demand and significantly raising 

AFUE. Two-stage and modulating combustion is common in gas furnaces and is an emerging 

technology in oil-fired furnaces.
3-62

stage combustion fan, a greater percentage of excess air is induced at the lower gas flow rate, 

resulting in lower combustion efficiencies when compared to the normal or maximum gas flow 

rate. Because of this, furnaces equipped with two-stage or modulating burners but without twostage or modulating combustion fans will always have lower energy efficiency, as measured by 

the DOE test procedure, than furnaces equipped with single-stage burners.

To overcome this lower efficiency and achieve efficient two-stage or modulating 

combustion, an induced draft or forced draft system using a two-speed or variable speed 

combustion fan must be paired with the two-stage or modulating burner. With the multi-speed 

combustion fan, the excess air drawn into the burner at low gas flow rates can be reduced in 

order to improve the steady-state efficiency of the furnace. 

Two-Stage and Modulating Oil Burners. Oil burners are typically oversized such that 

the design load is rarely met. Because oil-fired furnaces usually operate at part load, oil-fired 

furnaces suffer from significant stack losses and standby heat losses. To address poor field 

performance, two-stage and modulating oil burners have recently emerged on the oil-fired 

furnace market. Unlike their gas counterparts, oil burners are equipped with integrated 

combustion fans; and as such they do not need to be paired with an additional fan to achieve 

efficient reduced-rate operation. These advanced burners use smart controls to detect the heating 

load and determine low- or high-firing rates. In most cases, the reduced firing rate is sufficient to 

meet the heating load. Two-stage and modulating oil burners with two-stage and modulating 

combustion fans meet part-load demand with less excess heat lost through the flue, and therefore 

operate more efficiently, than single-stage oil burners. An initial calculation indicated that twostage and modulating combustion can increase AFUE by 5 percent when used in a residential oilfired furnace.64

3.3.3.5 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). This 

process is initiated by a blower that supplies an initial fuel and air mixture to the combustion 

chamber. A spark ignites the mixture. Once resonance is initiated, the process becomes selfsustaining. Pulse frequencies are on the order of 60 to 70 cycles per second.65

Pulse combustion systems feature high heat transfer rates, can self-vent, and can operate 

as isolated combustion systems. Because the pulse combustion process is highly efficient, the 

burners are generally used with condensing appliances. 

 The turbulent 

nature of the pulse combustion process requires no mechanical devices (e.g., induced draft fans 

or power burners) to vent the combustion products to the outside.

In contrast to furnaces that utilize natural draft and induced draft technologies, pulse

combustion furnaces generate positive pressure in the heat exchanger. This creates a potential 

safety problem because any breach in the heat exchanger would result in a leak of toxic 

combustion products into the circulation air stream. 
3-63

Pulse combustion gas furnaces were available in the United States for more than two 

decades, but they were withdrawn from the market because the manufacturers found that 

competing technologies such as condensing secondary heat exchangers cost significantly less to 

manufacture and operate. There are currently no pulse combustion furnaces available on the 

market.

3.3.3.6 Low NOx Premix Burners

Low NOx premix burners reduce emissions in two ways: by reducing peak flame 

temperature and by reducing levels of excess air. They achieve this by completely premixing the 

primary air and fuel prior to combustion, thereby eliminating the need for secondary air. The 

greater level of primary air in the lean, premixed air-fuel mixture creates a uniform flame shape 

that ensures oxygen availability to all regions of the flame. This eliminates the interior region of 

an inshot burner flame, where sub-stoichiometric, fuel-rich “hot spots” form “thermal NOx” at a 

rate that increases exponentially with flame temperatures above 2,800 °F. In addition, the 

absence of secondary air reduces the amount of free oxygen and nitrogen available to the flame 

exterior, thereby reducing “prompt NOx formation.” Aside from NOx reductions, the leaner, 

premixed flames also have a higher overall flame temperature than flames with secondary air. 

The hotter, leaner, premixed flame improves heat transfer and AFUE. It also raises the water 

vapor dew point, which facilitates condensation and further improves AFUE in condensing 

mode. The use of low NOx premix burners in a residential furnace would require a major 

redesign. As such, low NOx burners have not yet been successfully incorporated into a 

residential furnace design.

3.3.3.7 Burner Derating

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

geometry and surface area the same will increase the ratio of heat transfer surface area to energy 

input, thereby increasing the annual fuel utilization efficiency. However, the lower energy input 

means that less heat, and thus lower utility, would be provided than with conventional burner 

firing rates.

3.3.3.8 Insulation Improvements

The DOE test procedure requires that all non-weatherized furnaces shall be rated as 

isolated combustion systems and all weatherized furnaces shall be rated as outdoor installations. 

The test procedure specifies that the jacket loss for units intended for installation outdoors or in 

an unheated space may either be assigned a fixed value of 1% of the hourly input rating or a 

jacket loss measurement may be performed. If the jacket loss test is performed, insulation 

improvements may realize AFUE gains; therefore, DOE considered increasing or improving the 

insulation of a furnace. 

Insulation can be improved by modifying the baseline furnace design through the use of 

increased jacket insulation or advanced forms of insulation. 

Increased Jacket Insulation. Manufacturers insulate furnaces by adding insulation to the 

inside wall of the cabinet. Most residential furnaces on the market today, including weatherized 

furnaces, have 1⁄2-inch thick fiberglass insulation. Increasing the thickness of the jacket 
3-64

insulation could reduce standby losses by reducing heat loss through the jacket. Jacket losses 

represent a majority of the standby losses. Some manufacturers produce furnaces with increased 

insulation. 

Advanced Forms of Insulation. Alternate ways of reducing the jacket losses without 

increasing the footprint of furnaces include using advanced insulation materials or evacuated 

panels. Some of the advanced materials or methods of insulation considered here involve using 

foam insulation, vacuum insulation, inert gases, aerogel insulation, or partial vacuums. 

Foam Insulation. Foam insulation can be used as an alternative to fiberglass 

insulation. Chlorofluorocarbon-free, water-blown polyurethane foam is a common 

alternative to high-density fiberglass blankets. Incorporating foam insulation of the same 

thickness in place of fiberglass insulation can increase the overall efficiency of a furnace. 

Foam typically has an R-value up to two to three times greater than fiberglass. 

Additionally, foam can be blown into small spaces and constrictive geometries where the 

potential for heat loss still exists, and which would be difficult to fill with fiberglass batts. 

Finally, manufacturing processes that use foam-blowing techniques are better suited for 

production line changes due to the shape-conforming characteristics of the foam. This 

allows additional technology options, methods, and advances to be incorporated into 

current designs with minimal impacts on insulation installation techniques.

Vacuum Insulation Panels (VIP). A “hard” vacuum between internal reflective 

surfaces is a very good insulator. It has been used for years in Thermos bottles and Dewar 

tanks for cryogenic applications. Durability and the difficulty of maintaining the seal over 

the life of the furnace are some of the manufacturing problems that remain unresolved. 

This technology has not been demonstrated for use with furnaces.

Gas-Filled Panels (GFP). Gas-filled panels are thermal insulating devices that 

retain a high concentration of a low-conductivity gas at atmospheric pressure within a 

multilayer infrared reflective baffle. The thermal performance of the panels depends on 

the type of gas fill and the baffle configuration. Gas-filled panels are flexible and selfsupporting and can be made in a variety of shapes and sizes to thoroughly fill most types 

of cavities. This technology has not been demonstrated for furnace applications.66

Aerogel Insulation. Silica aerogel, an advanced insulation material, is composed 

of 96 percent air and 4 percent silicon dioxide. Aerogels are more efficient and weigh less 

than the fiberglass insulation currently used in most furnaces. The R-value of the aerogel 

at atmospheric pressure is comparable to that of polyurethane foam, but when 90 percent 

of the air is evacuated from a plastic-sealed aerogel packet, its resistance nearly triples. 

New manufacturing processes have been developed that can produce flexible blankets or 

clamshell forms of this material. The aerogel material is vulnerable to shock and 

vibration; however, material handling is an issue. Because the aerogel is hygroscopic, it 

requires a thorough sealing of the cavity between the heat exchanger and the cabinet. The 

material has not been demonstrated for use with furnaces. 

Evacuated Panels. Other materials with a lightweight open structure can provide 

effective insulation combined with “soft” or low vacuums. The materials can be enclosed 
3-65

with metals or plastic. A vacuum is drawn in this panel before sealing, and lightweight, 

rigid foam keeps the vacuum from compressing the panel. This technology has not been 

demonstrated for furnaces.

3.3.3.9 Off-Cycle 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 

furnace loses heat by natural convection and conduction through the combustion air inlet and 

flue. Installing a damper at these points can prevent heat from escaping and minimize off-cycle 

heat losses.

Dampers have no effect on the steady-state performance of the furnace; however, they

can reduce standby losses. The AFUE metric captures both steady-state and standby performance 

of the furnace, and thus any heated air that is retained in the system during the standby mode 

improves the system’s annual fuel utilization efficiency. 

The safety standard for gas-fired central furnaces, ANSI/AGA Z21.10.1-1993: “GasFired Central Furnaces,” requires the burner to shut off if the flue gets blocked. 67

Electro-Mechanical Flue Damper. A damper that is installed downstream of the heat 

exchanger is called a flue damper. Electro-mechanical flue dampers are activated by an external 

source of electricity. These dampers open when combustion starts and close immediately after 

combustion stops. When the damper reaches the open position, an interlock switch energizes the 

solenoid and enables the gas ignition circuit. Therefore, as a safety measure, the burner cannot be 

ignited when the damper is in the closed position. Because the dampers open and close 

immediately, no bypass is needed. The electro-mechanical flue damper needs an electrical 

connection and consumes a nominal amount of power during opening and closing.

Thus, the 

effects of a failure of the flue damper to open should be mitigated by the burner controls.

Electro-Mechanical Burner Inlet Damper. Inlet dampers are installed at the 

combustion-air inlet to the burner box and are designed to automatically close off the air passage 

and restrict the airflow through the heat exchanger when the burner is off. The principles and 

means of operation of an electro-mechanical inlet damper are identical to those of an electromechanical flue damper. 

3.3.3.10 Concentric Venting

Furnaces using outdoor combustion air may use a combustion air preheat venting 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. Manufacturers accomplish this preheat 

design by running the inlet and exhaust vents concentrically. The flue gases are exhausted 

through a central vent pipe and the intake 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. 
3-66

Concentric venting provides an efficiency advantage compared to conventional venting 

systems, as the concentric vent essentially serves as a shell-in-tube heat exchanger. Some furnace 

manufacturers report separate AFUE ratings for each model with both concentric and 

conventional venting. In such cases, models tested with concentric venting always show an 

efficiency enhancement of a few tenths of a percent AFUE over those with conventional venting 

configurations. 

3.3.3.11 Low-Pressure, Air-Atomized Oil Burner

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

retention head burner. This type of burner delivers oil to the fuel nozzle at pressures of 100 to 

150 pounds per square inch and is generally available at firing rates of more than 70,000 Btu/h. 

The fuel input rate is controlled by the size of the nozzle orifice. Pressure-atomizing 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 

Laboratory developed a low-pressure, air-atomized oil burner that can operate at firing rates as 

low as 0.25 gallons of oil per hour (10 kW). In addition, it can operate with low levels of excess 

combustion air (less than 10 percent) for lean-burning, ultra-clean combustion. A lower level of 

excess air generally improves AFUE rating. This single-stage burner design is also capable of 

firing fuel at high and low input rates, which are manually actuated by a switch, allowing it to 

closely match the smaller heating loads of well-insulated modern homes. The ability to derate the 

flame also greatly enhances the effectiveness of the heat exchanger, which improves steady state 

efficiency.

3.3.3.12 High-Static Oil Burner

A modification of the conventional flame retention head burner is the high-static pressure 

flame retention head oil burner. These burners employ an air guide to direct air onto the optimal 

point on the blower wheel and a scroll insert to create high static pressure in the combustion 

chamber while maintaining consistent air flow. This higher pressure enables the furnace to 

overcome restrictive flow passages in compact, more efficient, heat exchangers.68 These types of 

burners are also able to operate at lower levels of excess air, giving them a nearly 5 percent 

AFUE advantage over flame retention head burners.69,70

3.3.3.13 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 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.71 Testing at Brookhaven National Laboratory indicates that the typical 

efficiency benefit of delayed-action solenoid valves is expected to be less than 1 percent AFUE. 
3-67

3.3.4 Technologies Options That Do Not Improve AFUE

DOE preliminarily determined that the following technology options do not improve the 

fuel efficiency of furnaces: 

1. Infrared Burner

2. Improved Blower Efficiency

3. Micro Combined Heat and Power (Micro-CHP)

4. Positive Shut-Off Valve for Oil Burner Nozzles

These technologies were not carried forward to the screening analysis.

3.3.4.1 Infrared Burner

Infrared (IR) burners are typically premix burners that produce a high radiant heat flux 

with low NOx emissions. The primary mechanism of heat transfer in infrared burners is 

radiation, in which heat is emitted in the form of a wave. The infrared waves emitted by the 

burner are transmitted at the speed of light in a straight line without heating the air. When the 

waves strike an opaque object, they are absorbed and converted back to heat. The heated object 

can then dissipate its heat via conduction or convection.

Infrared burners have higher combustion efficiencies than traditional gas inshot burners. 

Gas and primary air flow through the porous material or fiber mesh of the burner without need 

for secondary air. Because they are able to operate at lower levels of excess air, infrared burners 

have a small combustion efficiency advantage over traditional blue-flame burners. 

Several infrared burner materials have been developed, including ceramic, stainless steel, 

and glass fiber. Most ceramic burners are flat plates, which have not been used in residential gas 

furnaces. Several ceramic burner designs consisting of ceramic fibers formed into a mat structure 

have been manufactured.72

Infrared burners made out of these materials are commonly used in industrial processing 

furnaces, room heaters, cooktop appliances, and other applications that require direct heating of 

an object. The application of IR burners to a residential furnace would require a major redesign 

of the heat exchanger to take advantage of radiative heat transfer from the burner. To DOE’s 

knowledge, IR burners have not been incorporated into a warm-air furnace design; and as such, it 

has not been demonstrated that IR burners can improve overall system efficiency.

This design satisfies the heating load requirements for residential 

furnaces, has very low NOx emissions, and is capable of operating within a very wide turndown 

ratio (the ratio of the maximum to minimum output). However, it has not been incorporated and 

demonstrated in a working residential furnace prototype. Another burner design incorporates 

perforated high-temperature stainless steel and woven high-temperature wire. These burners are 

formable and adaptable to various configurations; however, they are not very durable because the 

metal gets brittle with time, creeps out of shape, and cracks. Glass fiber is the most successful 

material because it can be formed and will reliably maintain its shape. 
3-68

3.3.4.2 Improved Blower Efficiency 

All furnaces come equipped with blower fans to circulate the heated air over the heat 

exchanger and through the plenum for distribution to the conditioned space. The efficiency of the 

air circulating blower can be increased by improving the blower motor efficiency and/or blower 

impeller efficiency to reduce the electrical energy consumption of the unit. However, electrical 

energy consumption of the furnace fan does not affect AFUE and therefore is not covered by this 

rulemaking.

3.3.4.3 Micro Combined Heat and Power (Micro-CHP)

It is possible to use the heat generated by a furnace's combustion system to generate 

electricity opportunistically.73, 74

3.3.4.4 Positive Shut-Off Valve for Oil Burner Nozzles

Self-generated electricity can be used to operate the electrical 

components of the furnace or can be sold back to the grid. Known methods of micro-CHP 

include fuel cell generators, thermophotovoltaic (TPV) generators, thermoelectric generators, 

and thermionic conversion. Other techniques use engines based on the Rankine cycle, Brayton 

cycle, Stirling cycle, or Otto cycle, where the engine drives an electrical generator or provides 

direct mechanical power and the waste heat from the engine is used for space heating. Neither 

the furnace’s electricity use nor the heat generated by its electrical components, however, 

contribute to the calculation of its seasonal efficiency. Therefore, this technology option will 

have no effect on AFUE.

One option for oil-fired furnaces is a positive shut-off valve on the fuel nozzle, which 

reduces smoke and soot production during burner start-up and shutdown.75

3.4 CENTRAL AIR CONDITIONER AND HEAT PUMP TECHNOLOGY 

ASSESSMENT

This valve is 

generally installed directly in the nozzle tip and prevents oil from dripping into the combustion 

chamber. This option can also be retrofitted on existing burners. A positive shut-off valve in an

oil burner nozzle does not affect the efficiency of the appliance, but plays a role as an emissioncontrol device. 

The purpose of the technology assessment is to develop a preliminary list of technologies 

that could potentially be used to improve the efficiency of central air conditioners and heat 

pumps. The following assessment provides descriptions of technologies and designs that apply to 

subsystems within all product classes of central air conditioners and heat pumps, as well as 

innovations that apply to heat pumps only.

3.4.1 Compressor Improvements

Several technologies exist to increase the efficiency of the compressors used in central air 

conditioner and heat pump systems. High efficiency reciprocating and scroll compressors, 

sometimes incorporating variable-speed motors, all have higher efficiencies than the traditional 

reciprocating compressors commonly used in air conditioners.
3-69

Scroll compressors compress gas in a fundamentally different manner from traditional 

compressors—between two spirals, one fixed and one rotating. High efficiency reciprocating 

compressors are as efficient, or more efficient, than scroll compressors. However, these 

compressors are often considered to present some drawbacks exist including noise, cost, and 

reliability, compared to scroll compressors.

Variable-speed compressors are implemented through the use of an electronic control on 

the compressor motor, which allows the motor to operate at different speeds. This feature 

typically increases efficiency over a broad operating range but does not inherently increase 

maximum efficiency at the compressor rating point. Variable-speed compressors reduce energy 

consumption in several ways:

1. When refrigerant flow is reduced during part-load operation, the condenser and 

evaporator (designed for full flow conditions) are more effective and thus more efficient.

2. Close matching of load eliminates the cycling that occurs with single-stage compressors, 

and cyclic losses penalize SEER and HSPF ratings. During the off-cycle, the pressure in 

the system equilibrates. At the intermediate pressure, refrigerant vapor will condense in 

the cold evaporator rather than the condenser. Essentially, some of the heat rejection load 

is rejected to the evaporator during this time, reducing overall system performance. 

Variable speed operation would eliminate or significantly reduce compressor off-time 

and the related inefficiencies.

3. Reduced pressure rise across the compressor at lower capacity also improves efficiency 

by requiring less pumping power. Maintaining a constant pressure is more efficient 

because losses at higher pressure rise are greater than gains at lower pressure rise.

3.4.2 Fan System Improvements

3.4.2.1 Higher Efficiency Fan Motors

Fan motors are fractional horsepower in size, are responsible for moving air across the 

indoor and outdoor coils, and typically run at one speed. The manufacturer will match the motor 

size and fan blade to the coil to meet the expected cooling load under most conditions. Higher 

efficiency fan motors reduce energy consumption by requiring less electrical power to generate 

motor shaft output power.

Electric motors operate based on the interaction between a field magnet and a magnetic 

rotor. In a brushed motor, the field magnets are permanent magnets and the rotor is an 

electromagnet; the situation is reversed in a brushless motor. The electromagnetic interactions 

between these two magnets cause the rotor to rotate.

Nearly all fan motors for standard central air conditioners and heat pumps are of the 

permanent split capacitor (PSC) variety. In PSC motors, the electromagnet consists of windings 

of electrical wire through which current is driven. Through electromagnetic induction, this 

magnetic field induces current in the conductor bars of the rotor. The conductor bars of the rotor, 

often made of copper or aluminum, are arranged in such a manner that they produce another 

magnetic field once current is induced. The interaction of the magnetic field of the electromagnet 
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and the magnetic field of the rotor results in rotation of the rotor. A smaller, start-up winding is

present in addition to the main winding. The start-up winding is electrically connected in parallel 

with the main winding and in series with a capacitor. At start up, the interactions between the 

magnetic field generated by the start up winding and that generated by the main winding induce 

rotation. Because of the capacitor, however, the current to the start-up winding is cut off as the 

motor reaches steady state. PSC motors are produced in large quantities and are relatively 

inexpensive with motor efficiencies ranging from 50 to 70 percent.

Electronically commutated motors (ECM) are brushless permanent magnet motors with 

motor efficiencies between 70 and 80 percent, making them more energy efficient than PSC 

motors. Like a PSC motor, the stator of an ECM is an electromagnet used to produce a magnetic 

field. Unlike the PSC motor, the rotor of an ECM consists of a permanent magnet. The 

interaction of the magnetic field of the electromagnet and the magnetic field of the permanent 

magnet rotor result in rotation of the rotor. ECMs generally operate more efficiently than PSC 

motors. While PSC motors operate most efficiently at a single speed with significantly 

diminishing operating efficiency at others, ECMs are capable of maintaining a high operating 

efficiency at multiple speeds. However, ECMs can weigh twice as much as equivalent PSC 

motors. In addition, ECMs are complex, and can be significantly more expensive than PSC 

motors.

A way to further improve the efficiency of motors used for central air conditioner and 

heat pump applications is to make the critical components of an induction motor's rotor (e.g., 

conductor bars and end rings) out of copper instead of aluminum. Due to difficulties with casting 

copper, making these components out of aluminum is the common current practice. However, 

the greater conductivity of copper results in lower resistance heating losses in the rotor, and thus 

lower losses in the motor when compared to traditional aluminum motor parts. Recently, the 

creation of copper dies made from special alloys has allowed for the advancement of copper 

casting techniques. Additional improvements in the design and fabrication of copper motors, 

such as optimization of the steel laminations, could further increase the efficiency of copper 

motors over aluminum motors.

3.4.2.2 Higher Efficiency Fan Blades

High efficiency fan blades move air more efficiently, yielding energy consumption 

savings by reducing the required fan shaft power. The fans typically used in central air 

conditioners and heat pumps have stamped, curved sheet metal blades. The blades are typically 

supplied by a fan blade manufacturer and mounted to the motor by the manufacturer. 

Consequently, they are not likely to be optimized for the particular central air conditioner or heat 

pump that they are installed on. Fans may have lower efficiencies due to the higher required 

pressure drops, for which sheet metal fans are not well suited. Required fan shaft power could be 

reduced if the fan blades were optimized for each given application.

3.4.3 Expansion Valve Improvements

Expansion valves are refrigerant metering devices whose purpose is to control the amount 

of refrigerant flowing to the evaporator coil. In doing so, they simultaneously decrease the 

temperature and pressure of the refrigerant, creating a cold liquid-vapor mixture. The low 
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temperature of the refrigerant leaving the expansion valve creates the driving force to move heat 

out of the refrigerated space and into the evaporator.

The most basic type of expansion device is a capillary tube, which may be found in older, 

less efficient air conditioners and heat pumps. The capillary tube is a long, thin piece of pipe that 

creates a pressure drop in the refrigerant through frictional losses. Capillary tubes must be sized 

to the particular application and cannot adjust for variations in load or ambient operating 

conditions. They are often oversized for worst-case conditions, and therefore may operate at 

reduced efficiency during normal operation.

The thermostatic expansion valve (TXV) is common in air conditioners and heat pumps 

rated at an efficiency level of 13 SEER or above. This device uses an orifice to reduce the 

pressure of the entering refrigerant and a sensing bulb to monitor and maintain the temperature 

of the superheated vapor leaving the evaporator. Because the TXV allows for some degree of 

adjustment of refrigerant expansion, it may be somewhat more efficient than the capillary tube 

device under varying conditions.

The electronic expansion valve (EEV) is similar to the TXV, but uses an electronic 

control system to optimize refrigeration-system performance under all operating conditions. 

Because it does this with greater flexibility than that allowed by a TXV, an EEV theoretically 

allows for further increases in energy efficiency under varying conditions when paired with 

advanced modulating systems.

3.4.4 Heat Exchanger Technologies and Improvements

3.4.4.1 Baseline Technology

Most residential central air conditioners and heat pumps currently on the market utilize 

traditional tube-and-fin heat exchangers for both the evaporator and condenser coils. These coils 

are refrigerant-to-air heat exchangers composed of metals with high thermal conductivity, 

usually aluminum and copper, with the tubes generally being composed of copper and the fins of 

aluminum.

The evaporator coil is responsible for evaporating and superheating the entering 

refrigerant liquid-vapor mixture while extracting heat from the air in the conditioned space. The 

internal heat-exchanging surfaces in contact with refrigerant are commonly referred to as

“refrigerant-side” while the external heat-exchanging surfaces in contact with the air are referred 

to as “air-side.” Because a temperature difference is necessary to drive heat from the air into the 

refrigerant, the saturated evaporator temperature must be considerably colder than the 

evaporator’s discharge air temperature. The magnitude of this driving force is directly related to 

the total cooling load and the thermal characteristics of the evaporator.

The condenser coil is responsible for condensing and sub-cooling the entering refrigerant 

vapor while rejecting heat from the refrigerant to the ambient air.

The majority of evaporator and condenser coils used in central air conditioners and heat 

pumps currently on the market are of the traditional tube-and-fin heat exchanger design. Many 

manufacturers utilize a similar process in building coils, and this methodology has remained 
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fundamentally the same over the long period during which these products have been in use. The 

actual techniques utilized in this process vary by company, and proprietary methods are often 

utilized by specific manufacturers in the production of coils. Manufacturing of coils in-house is a 

process which requires high capital investments in machinery and line setup. As a result, 

manufacturers have been hesitant to move away from the traditional method of coil production, 

as doing so would require large new investments. Instead, companies have historically focused 

on improving the performance of their existing coil designs.

3.4.4.2 Improvements to Baseline Coils 

Increasing the overall size of the coil in one or more dimensions tends to be the most 

cost-effective way to increase the system efficiency. Increasing the area of the evaporator coil 

decreases the necessary temperature difference and therefore decreases the required saturated 

evaporator temperature. Increasing the area of the condenser coil decreases the necessary change 

in temperature across the coil. Both result in increased compressor efficiency (increased EER 

and reduced energy consumption). However, many applications limit the amount of coil size 

increase in order to maintain overall cabinet dimensions. Most approaches to increasing the coil 

surface area also result in an increase in required fan motor power and an increase in refrigerant 

pressure drop. Enhancements to the refrigerant-side surface area of both evaporator and 

condenser coils typically include rifled or diamond-pattern tubing and increased number of tube 

passes. Enhancements to the air side surface area include increased fin pitch (decreased fin 

spacing), fin patterns (wavy or zig-zag), and increased numbers of tube passes. The size 

constraints facing manufacturers who have already maximized the size of their units make it 

necessary for these companies to consider alternative methods to improving heat exchanger 

performance.

3.4.4.3 Alternative Coil Technologies

Liquid Suction Heat Exchangers. The function of a liquid suction heat exchanger is to 

further cool the flow of liquid refrigerant entering the expansion valve using the flow of gaseous 

refrigerant leaving the evaporator, thus providing sub-cooling for the entering liquid by superheating the exiting suction vapor. Hotter suction vapor is less susceptible to heat gains in the 

return piping to the compressor rack. The compressor work is increased, however, because the 

suction vapor has greater enthalpy. In addition, the possibility of compressor overheating 

problems, brought on by the combination of increased compressor work and hotter vapor, limits 

the use of this method in some situations. The possibility for these problems and the potential 

gains of liquid suction heat exchangers depend on the several factors, including evaporator 

temperature, type of refrigerant used, and system pressures. These potential issues indicate that 

the performance of an LSHX is dependent upon a number of factors, including refrigerant type, 

operating temperature, and ambient conditions, and thus DOE does not have enough information 

to suggest that an LSHX would consistently increase SEER or HSPF as rated using the DOE test 

procedure. Consequently, DOE did not consider LSHXs as a design option in the engineering 

analysis. 

Microchannel Heat Exchangers. Several companies produce microchannel heat 

exchangers, which are mainly used in the automobile industry. Unlike a conventional round-tube 

plate-fin heat exchanger, the microchannel has a rectangular cross-section containing several 
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small channels through which refrigerant passes. Fins pass between the tubes and are brazed to 

the tubes, and all components are aluminum. The resulting microchannel coil transfers more heat 

per unit of face area than does a round-tube plate-fin coil of comparable capacity. It does so with 

a lower airside pressure drop, yielding reduced fan power consumption. These benefits can 

improve system EER and SEER ratings in residential air conditioners when compared to a 

condenser coil of the same face area. This would allow manufacturers to improve the rated SEER 

without further increasing the size of the units. 

Although the microchannel heat exchanger costs more to produce than a conventional 

round-tube plate-fin coil, this product offers particular opportunities to reduce the size and 

weight of the heat exchanger. Those advantages led to the rapid and almost total transition of the

automobile air conditioner market to microchannel technology. Microchannel heat exchangers 

also offer significant reductions in refrigerant charge, which suggests that they may reduce the 

rate of compressor failures caused by refrigerant slugging.

Even after several years of dominance in the automobile market, the microchannel heat 

exchanger has not penetrated the building air conditioning markets where size and weight 

constraints are not as important. The cost advantages of reducing the size and weight of the 

condenser or the capacity of the system have not sufficiently outweighed the added costs and risk 

associated with the microchannel technology for these systems to attain widespread use in 

building applications to date. Additionally, given the fact that most manufacturers produce coils 

in-house, and that setting up a coil production line is an extremely capital-intensive process, 

manufacturers are generally hesitant to make the large investments needed to move away from 

the production of traditional tube-and-fin heat exchangers. Moreover, several limitations and 

uncertainties are particularly hindering the large-scale adoption of microchannel heat 

exchangers. First, microchannel construction makes condensate removal much more challenging

than traditional tube-and-fin heat exchangers. This poses a serious barrier to the adoption of the 

technology in evaporators and in heat pump condensers. Some manufacturers may decide not to 

adopt the new technology if they cannot offer it in all of their products, including both air 

conditioners and heat pumps. Second, there are concerns whether residential microchannel heat 

exchangers are proven to perform well under wide variations in ambient temperatures given that 

they are considerably larger than automobile heat exchangers and are configured differently. 

Third, compressor lubrication is entrained in the refrigerant, and residential microchannel heat 

exchangers must display a proven ability to consistently return lubricant to the compressor to 

avoid costly damage. Fourth, manufacturers are concerned that contractors will not be able to 

repair coil leaks effectively because of the difficulty of successfully brazing aluminum in the 

field.

Flat-Tube Heat Exchangers. Flat-tube, louver-fin heat exchangers offer various 

advantages over traditional round-tube, plain-fin heat exchangers. The flat-tube design reduces 

wake region, which decreases heat transfer downstream of round tubes. The design improves fin 

efficiency and creates a lower profile drag as a result of the smaller tube projected area. 

Serpentine louvered-fin, flat-tube heat exchangers have already been utilized in automotive 

applications because of their ability to produce the same amount of heat transfer with much more 

compact designs than the plain-fin, round-tube variety heat exchangers. In laboratory tests, the 

louver-fin, flat-tube heat exchanger was found to produce heat transfer coefficients that were 

90% higher than those produced by a plain-fin, round-tube heat exchanger76. The significant 
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increase in heat transfer coefficient resulted in a size reduction factor of two to three for a 

residential absorption heat pump system. The more efficient flat-tube heat exchangers would be 

able to provide the same amount of heat transfer and reduce the amount of airflow needed from 

the fans, thus reducing the amount of electricity consumed by the fan motors and increasing

system efficiency.

Like the microchannel technology, the flat-tube heat exchangers still have not broken 

through into the air conditioner and heat pump market, where the size of the unit is not as much 

of a concern. The extra cost of developing these systems and investing the large amounts of 

capital needed to produce them in-house has not yet been offset by the potential advantages to 

using flat-tube heat exchangers. Also, condensate removal is a concern in louvered-fin, flat-tube 

heat exchangers because of water “bridges” that get into the louver gaps and reduce heat transfer.

3.4.5 Inverter Technology

Inverter technology can improve air conditioner and heat pumps efficiency through more 

efficient control of the fan motors and compressor. The incoming AC current is converted to DC 

current by a rectifier and then back to AC current at a specific frequency by an inverter. This AC 

current is used to drive the motor or compressor, whose speed is calibrated to the frequency of 

the AC current. Though there are other ways to change motor speed, inverter technology allows 

for standard AC fans motors and compressors to maintain efficiency at variable speeds. The 

ability to vary capacity as needed allows for inverter driven components to avoid cycling on and 

off as much as non-inverter driven components. This reduces the fluctuations in temperature of 

the conditioned space and also helps to extend component lifetime. 

In terms of SEER and HSPF, the benefits of inverter technology are seen through more 

efficient operation of the motors and compressor. Reduction of a unit’s power draw during the 

applicable tests increases either the SEER or HSPF rating produced by the test. Because inverter 

driven compressors and fan motors can operate at partial loads, manufacturers are more likely to 

conduct the optional cyclic C and D tests to determine the degradation coefficient (Cd

3.4.6 Designs Relevant Only to Heat Pumps

) instead of 

using the default value of 0.25.

The following technologies, defrost mechanisms and defrost cycle control, are two 

examples of defrost-related improvements applicable to heat pump designs. They are not 

intended to comprise an exhaustive list of viable technologies.

3.4.6.1 Defrost Mechanisms

As the outside air passes over the outdoor coil of a heat pump operating in heating mode, 

its heat is absorbed by the refrigerant inside the coil, which lowers the temperature of the 

ambient air. When the temperature of the surrounding air is reduced to less than 32°F, the 

moisture in the air will condense and freeze on the outdoor coil, forming a layer of frost. The 

frost reduces performance by increasing the thermal resistance to heat transfer from the coil to 

the air and by obstructing airflow. Both the method in which defrost is performed and control of 

the defrost cycle can lead to increased energy savings.
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The standard method of defrosting the outdoor coil during the heating operation of a heat 

pump is to temporarily reverse the flow of the refrigerant. This will use some of the heat from air 

inside to heat the outdoor coil and melt the frost. At the same time the indoor coil is cooled, and 

it becomes necessary to heat the house using an auxiliary heating system (typically electric 

resistant heaters).

“Frost-less” heat pump defrost technology slows frost accumulation on the outdoor coil 

while also increasing the heating capacity by adding an accumulator to the heat pump cycle. The 

accumulator traps heat from the condensed liquid from the condenser, and this causes an increase 

the suction pressure of the compressor. This addition of heat to the accumulator increases the 

outdoor coil temperature by several degrees and thus reduces the frost accumulation on the coil. 

Also, much of the heat added to the accumulator is still brought inside by increased heat pump 

supply air temperature since the suction pressure of the compressor was increased. The frostless 

heat pump still may accumulate frost, however, if the heat pump is operated for a long period of 

time at low ambient temperatures, creating the need for a cycle reversal for defrosting. During 

the reverse cycle, the indoor blower is shut off and the refrigerant flows to the accumulator, 

making the accumulator take over the function of the evaporator. This allows for reverse cycle to 

defrost while also preventing cool air from being blown inside and reduces the need for 

resistance heaters. When the surrounding temperature drops below 32°F, increasing the 

temperature of the outdoor coil a few degrees will not prevent frost accumulation, and heat input 

to the accumulator becomes useless. Therefore, the accumulator should only be used at 

temperatures between 32°F and 41°F, when frost is most likely to collect on the coil and the use 

of the accumulator will be able to reduce the amount of frost. Therefore, this technology is only 

effective within a small range of ambient temperatures at and above the freezing point of water. 

Additionally, such systems increase compressor work and thus do not appear to have any 

positive benefit on rated SEER or HSPF values as measured using the DOE test procedure.

Another mechanism for reducing the number and duration of defrost cycles is hot watersource defrosting. In heat pumps equipped with hot water defrost, a specifically designed system 

of valves and conduits allow the heat pump to selectively send the refrigerant to the various heat 

pump components, depending on which heat pump functions are being performed. These heat 

pumps use components and valves arranged in such a way that they are able to cool a space, heat 

a space, heat a liquid without affecting the temperature of the conditioned space, cool a space 

while heating a liquid, and defrost the outdoor coil using only the previously heated water as a 

heat source. During the defrost mode, hot water that is held in a storage tank is used to defrost 

the outdoor coil, without degrading the overall performance of the heat pump, but reducing the 

heating capacity. A refrigerant-to-water heat exchanger is used to provide energy to the 

refrigerant and allow it to melt the frost on the outdoor coil. The energy taken from the hot water 

in the system is easily and inexpensively replaced when the heat pump switches back into normal 

heating mode because it reduces the need for costly supplemental heat provided by electric 

resistance heaters. However, such a system would make no impact on the values of SEER or 

HSPF determined using the DOE test procedure. Consequently, DOE did not consider either of 

these defrost mechanisms as design options in the engineering analysis. DOE is not aware of any 

defrost mechanisms other than frost-less heat pumps or hot-water defrost that are currently in use 

on the market or in development that could have a potential benefit to rated SEER or HSPF. 
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3.4.6.2 Defrost Cycle Control

During a conventional heat pump defrost cycle some form of supplemental heating is 

needed to compensate for the reversal of the heat pump cycle. Usually electric resistance heaters 

are used to heat air inside the house while the defrost cycle occurs, and this type of heating is 

much less efficient than heating using the heat pump. Since the alternate heat sources are much 

less efficient, the efficiency of a heat pump can be increased by reducing the frequency and 

duration of the defrost cycles.

Defrost cycle control involves management of the initiation and termination of defrost 

cycles, and thereby the frequency and duration of defrost cycles. In conventional heat pumps 

defrost cycles are typically scheduled, and initiation and termination are timer-controlled. For 

this type of defrost cycle control, cycles are initiated at regular intervals and terminated after a 

fixed amount of time. Cycle frequency and duration are unrelated to actual frost conditions and 

are just based on estimations by the manufacturer. Under timer control, the frequency of defrost 

cycles is determined by the amount of time the manufacturer expects it to take for a large frost 

layer to develop in the worst-case scenario and by a cycle duration long enough to ensure 

complete defrost in the worst-case scenario. Timer-based defrost can lead to unnecessarily 

frequent and long defrost cycles.

Demand-based defrost cycles eliminate unnecessary defrost cycles. Demand-defrost heat 

pumps use sensors to measure outdoor coil and outdoor ambient conditions to determine when to 

initiate and terminate defrost cycles. A microprocessor examines and analyzes the compressor 

run time, ambient air temperature, and outdoor coil temperature, all of which determine the 

environment under which a defrost cycle should occur. The microprocessor is then able to 

determine when the defrost cycle should be initiated and when it should be terminated, reducing 

the overall number and duration of cycles and improving the efficiency of the heat pump.

A defrost cycle control system is set up to adapt from previous defrost cycles to attain 

improved defrost system operation at various outdoor temperature conditions. This technology 

can save energy annually by using a computer to run the defroster at the optimum time and 

optimum temperature based on the ambient temperature range. However, this system adds 

efficiency because it helps account for outdoor temperature variation. While the static nature of 

the DOE test procedure ambient conditions does not allow for increases in SEER or HSPF due to 

implementation of such a system, the test procedure contains a demand defrost credit for units 

with such controls, which allows for an increase to HSPF.

3.4.6.3 Three Stage Heat Pumps

Three stage or “triple capacity” heat pumps have an additional compressor to provide 

additional capacity at low ambient temperatures. This enables the heat pump to operate more 

efficiently than a two stage or single stage unit at lower temperature because a three stage heat 

pump requires less supplemental resistance heating. Rheem commented that equipment utility 

has not been proven sufficiently to consider them, while Ingersoll Rand stated that HSPF’s for 

three stage heat pumps are not noticeably higher as tested according to the DOE test procedure. 

(CAC: Rheem, No. 76 at p. 11;CAC: Ingersoll Rand, No. 66 at p. 9) DOE agrees with these 

comments and believes there is no benefit to performance metrics according to the DOE test 
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procedure, and therefore, will not consider three stage heat pumps further in the downstream 

analyses. 

3.4.7 Solar Assisted Central Air Conditioners and Heat Pumps 

One way to reduce the electrical consumption of an air conditioner or heat pump is 

through the use of solar energy. Solar panels are connected to the system and used to provide 

some of the power necessary for the unit to run. While solar-assisted systems are still partially 

dependent on conventional sources of electricity, they can be beneficial for reduction of peak 

demand electricity usage. 

Solar assist does not increase the operating efficiency of the unit. While such solarassisted units may reduce demand for electricity from the grid, the unit will still need the same 

amount of power regardless of the power source. Consequently, there is no benefit for SEER or 

HSPF ratings as tested by the DOE test procedure, and therefore, solar assist technology was not 

considered further in the analysis.

3.5 STANDBY MODE AND OFF MODE TECHNOLOGY ASSESSMENT

Section 310(3) of EISA 2007 amended EPCA to require that energy conservation 

standards address standby mode and off mode energy use. Specifically, when DOE adopts a 

standard for a covered product after July 1, 2010, it must, if justified by the criteria for adoption 

of standards in section 325(o) of EPCA, incorporate standby mode and off mode energy use into 

the standard, if feasible, or adopt a separate standard for such energy use for that product. (42 

U.S.C. 6295(gg)) 

For air conditioners and heat pumps, the standby mode is in effect when the system is on 

but the compressor is not running, i.e., the system is not actively heating or cooling but the 

compressor is primed to be activated by the thermostat. Thus, the standby mode for air 

conditioners functions during the cooling season and for heat pumps during both the cooling and 

heating seasons. Correspondingly, the off-mode generally occurs for air conditioners during all 

non-cooling seasons and for heat pumps during the “shoulder seasons” (i.e., fall and spring)

when consumers neither heat nor cool their homes. The SEER and HSPF metrics already account

for standby mode but not off mode energy use because off mode energy use occurs outside of the 

seasons to which these descriptors apply. Incorporation of the off mode into these descriptors 

would mean that they would no longer be seasonal descriptors. Thus, because EPCA requires 

use of these descriptors for central air conditioners and heat pumps (see 42 U.S.C. 6291(22) and 

6295(d)), it would not be feasible for DOE to incorporate off mode energy use into a single set of 

standards for central air conditioners and heat pumps. Therefore, DOE is adopting separate off 

mode standards that are maximum wattage (W) levels, which address such energy use. DOE also 

presents corresponding trial standard levels (TSLs).

3.5.1 Design Options Applicable to All Products

DOE identified the following design options as having the potential to reduce the 

electrical power consumption of a furnace operating in standby mode or a central air conditioner 

or heat pump operating in off mode:
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1. Toroidal Transformer

2. ECM Control Relay

3.5.1.1 Toroidal Transformer

A toroidal transformer operates more quietly and efficiently than a typical laminated 

power transformer and has lower noise-inducing stray magnetic fields and smaller size and 

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

silicon steel ribbons. The steel ribbons are arranged such that all their molecules are aligned with 

the direction of flux. This allows better performance than a traditional laminated transformer, in 

which unaligned molecules increase the core’s reluctance, or capacity for opposing magnetic 

induction. 77

Toroidal transformers also have virtually no air gap because they are made of 

continuously wound ribbon. Eliminating the air gap minimizes flux leakage, which is the 

principle source of power loss in a laminate transformer, such that nearly all flux is utilized. 

Additionally, toroidal transformers have a copper coating that reduces heat (i.e., power) loss. 

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 percent. 

Because transformers continue to supply power to the control board in all modes of 

operation, including standby mode, increasing their operating efficiency will reduce the 

furnace’s standby electrical power consumption. However, although toroidal transformers have 

significant advantages over laminated transformers in efficiency, size, and weight, they are also 

more expensive to manufacture. Their tight, ring-shaped windings may make large scale 

manufacturing difficult, especially in contrast with the simple windings of a rectangular, 

laminated transformer design.

3.5.1.2 ECM Control Relay

During testing of standby and off mode components, DOE found that ECM motors and 

their associated controls consumed 3 watts in off mode, while PSC motors did not have any off 

mode power draw. Therefore, the ECM motor could be disconnected to further reduce a 

system’s off mode power consumption. To accomplish this task, a control relay would need to be 

added to the circuit. 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. However, DOE has not 

found any products which completely disconnect the ECM fan motor. Additionally, 

manufacturer feedback indicated that ECM motors are subjected to large currents upon start up 

and using a control relay to completely depower them could reduce the lifetime of the motors.

3.5.2 Standby Mode Design Options Applicable Only to Furnaces

3.5.2.1 Switching Mode Power Supply

DOE identified switch mode power supplies as having the potential to reduce the 

electrical power consumption of a furnace operating in standby mode. While linear power 

supplies regulate voltage supply to the dc circuit with a series element, switching mode power 
3-79

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 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.

Switching mode power supplies also allow the use of a smaller transformer than a linear 

power supply. This is because the size of the transformer (i.e., the number of turns) is inversely 

related to power frequency. In one respect, switching mode power supplies are at a relative 

disadvantage in comparison to linear power supplies, which regulate voltage with greater 

precision and have simpler controls.

3.5.3 Off Mode Design Options Applicable Only to Central Air Conditioners and Heat 

Pumps

3.5.3.1 Thermostatically Controlled Crankcase Heaters

One option for reducing off mode power consumption is to thermostatically control the 

crankcase heater. While the added components will consume a small amount of additional 

power, the energy savings from more efficient use of the crankcase heater outweigh the added 

power consumption of these components. Manufacturer feedback indicated that in most units the 

crankcase heater turned on whenever the compressor cycled off. However, in some situations, 

the crankcase heater is not needed to prevent refrigerant migration or condensation in the 

compressor crankcase. A small disc thermostat on the unit to measure the outdoor ambient 

temperature, along with associated relay and wiring, can be used to regulate the crankcase heater 

does not come on unless needed. 

Alternatively, the thermostat could be placed on the compressor itself and measure the 

shell temperature to determine when the crankcase heater is needed. However, DOE believes that 

scroll compressors are not currently equipped to accommodate a temperature sensor on the 

compressor shell, whereas reciprocating compressors are. By considering temperature sensors 

based on compressor shell temperature, DOE believes that manufacturers of scroll compressors 

would be unfairly impacted and that the market might be driven towards reciprocating 

compressors. Therefore, DOE decided not to include crankcase heaters, which are controlled 

based on compressor shell temperature in the analysis, and only considered crankcase heaters 

with a control strategy based on outdoor ambient temperature. 

3.5.3.2 Self-Regulating Crankcase Heaters

Self-regulating or variable resistance crankcase heaters are similar in appearance to 

conventional crankcase heaters but are able to vary their resistivity as a function of outdoor 
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ambient temperature. Varying the resistivity alters the current flowing through the crankcase 

heater, which in turn increases or decreases the power consumed by the crankcase heater. This 

variable resistivity is accomplished through a polymer core which expands as temperature 

increases, thereby disconnecting electrical pathways. Because they are self-regulating, these 

crankcase heaters do not require a thermostat to control them. However, there are potential 

additional energy savings through the pairing of a self-regulating crankcase heater with a 

thermostat. Additionally, a self regulating crankcase heater would have a lower power draw 

when used in conjunction with a compressor cover because of the thermal insulation provided by 

the cover, while a fixed resistance crankcase heater would have a constant power draw. 

As part of the final rule analysis, DOE conducted off mode testing and found for heat 

pumps that the self regulating crankcase heaters did not reduce power consumption as compared 

to conventional crankcase heaters. Therefore, DOE believes that manufacturers will choose to 

install the conventional crankcase heater because it is cheaper and has a lower power draw than 

the self-regulating crankcase heater. Since the self-regulating crankcase heaters fail to improve 

efficiency according to the proposed off mode test procedure for heat pumps (75 FR 21224-

31271), DOE only considered them further in the off mode analysis for air conditioners. 

3.5.3.3 Compressor Insulation Cover

Some products have a cover over the compressor for noise reduction. While the main 

intent of these sound blankets is to minimize compressor noise, they provide a certain amount of 

thermal insulation to the compressor. This cover prevents the compressor shell from cooling as 

quickly when the compressor shuts off. If a variable resistance crankcase heater is used with this 

compressor cover, then the crankcase heater will have a lower power draw because of the 

thermal insulation provide by the cover. By allowing the crankcase heater to have a lower power 

draw, the cover helps to reduce the amount of off mode power consumption as measured by the 

proposed test procedure (75 FR 21224-31271).
3-81

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