CHAPTER 3. MARKET AND TECHNOLOGY ASSESSMENT 

TABLE OF CONTENTS 

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

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

3.1.2 Product Classes...................................................................................................... 3-2
 

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

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

3.2.1 Trade Associations ................................................................................................ 3-4
 

3.2.2 Manufacturers and Market Share .......................................................................... 3-5
 

3.2.3 Regulatory Programs............................................................................................. 3-8
 

3.2.4 Non-Regulatory Programs................................................................................... 3-10
 

3.2.5 Industry Cost Structure........................................................................................ 3-15
 

3.2.6 Equipment Lifetime............................................................................................. 3-16
 

3.2.7 Market Performance Data ................................................................................... 3-17
 

3.2.8 Historical Shipments and Efficiencies ................................................................ 3-27
 

3.2.9 Saturations in U.S. Households........................................................................... 3-30
 

3.3 TECHNOLOGY ASSESSMENT................................................................................... 3-31
 

3.3.1 Compressor Improvements.................................................................................. 3-31
 

3.3.2 Fan System Improvements .................................................................................. 3-32
 

3.3.3 Expansion Valve Improvements ......................................................................... 3-33
 

3.3.4 Heat Exchanger Technologies and Improvements.............................................. 3-34
 

3.3.5 Designs Relevant Only to Heat Pumps ............................................................... 3-37
 

3-i 
LIST OF TABLES 

Table 3.2.1 AHRI Directory of Certified Product Performance Classifications for Residential 

Central Air Conditioners and Heat Pumps................................................................................... 3-5
 

Table 3.2.2 Manufacturer Brand Names Found in the AHRI’s Directories of Certified Product 

Table 3.2.3 Current Federal Energy Conservation Standards for Residential Central Air 

Table 3.2.4 Canadian Energy Conservation Standards for Residential Central Air Conditioners 

Table 3.2.5 ENERGY STAR Levels for Split System and Single Package Residential Central Air 

Table 3.2.8 Rebate Programs Offered by Local Utilities for Residential Central Air Conditioners
 

Table 3.2.9 Rebate Programs Offered by Local Utilities for Residential Central Air-Cooled Heat 

Table 3.2.10 Air Conditioning and Warm Air Heating Equipment Industry Employment and 

Table 3.2.12 Industry Cost Structure Developed from SEC Data Error! Bookmark not defined.
 

Table 3.2.13 Types of Models Listed in the AHRI Directory of Certified Product Performance....
 

Performance for Residential Central Air Conditioners and Heat Pumps .................................... 3-6
 

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

and Heat Pumps ......................................................................................................................... 3-10
 

Conditioners and Heat Pumps.................................................................................................... 3-11
 

Table 3.2.6 CEE Tiers for Residential Central Air Conditioners and Heat Pumps................... 3-12
 

Table 3.2.7 Federal Tax Credits for Residential Central Air Conditioners and Heat Pumps.... 3-12
 

.................................................................................................................................................... 3-13
 

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

Payroll Data ............................................................................................................................... 3-15
 

Table 3.2.11 Air Conditioning and Warm Air Heating Equipment Industry Cost Data .......... 3-16
 

.................................................................................................................................................... 3-17
 

LIST OF FIGURES 

Figure 3.2.1 2007 Market Shares for Unitary Air Conditioners and Heat Pumps...................... 3-7
 

Figure 3.2.3 SEER Ratings for Single Package Central Air Conditioners in the AHRI Certified 

Figure 3.2.4 SEER Ratings for Single Package Heat Pumps in the AHRI Certified Product 

Figure 3.2.5 SEER Ratings for Split System Central Air Conditioners in the AHRI Certified 

Figure 3.2.6 SEER Ratings for Split System Heat Pumps in the AHRI Directory of Certified 

Figure 3.2.7 SEER Ratings for SDHV Systems in the AHRI Directory of Certified Product 

Figure 3.2.8 HSPF Ratings for Single Package Heat Pumps in AHRI’s Directory of Certified 

Figure 3.2.9 HSPF Ratings for Split System Heat Pumps in AHRI’s Directory of Certified 

Figure 3.2.10 HSPF Ratings for SDHV Heat Pumps in AHRI’s Directory of Certified Product 

Figure 3.2.11 Average SEER Ratings at Each Cooling Capacity for Single Package Air 

Product Performance Directory ................................................................................................. 3-18
 

Performance Directory............................................................................................................... 3-18
 

Product Performance Directory ................................................................................................. 3-19
 

Product Performance.................................................................................................................. 3-19
 

Performance ............................................................................................................................... 3-20
 

Product Performance.................................................................................................................. 3-21
 

Product Performance.................................................................................................................. 3-21
 

Performance ............................................................................................................................... 3-22
 

Conditioners in AHRI’s Directory of Certified Product Performance ...................................... 3-23
 

3-ii 
Figure 3.2.12 Average SEER Ratings at Each Cooling Capacity for Split System Air 

Conditioners in AHRI’s Directory of Certified Product Performance ...................................... 3-23
 

Figure 3.2.13 Average SEER Rating at Each Cooling Capacity for Single Package Heat Pumps 

Figure 3.2.14 Average SEER Rating at Each Cooling Capacity for Split System Heat Pumps in 

Figure 3.2.15 Average SEER Rating at Each Cooling Capacity for SDHV Systems in the AHRI
 

Figure 3.2.16 Average HSPF at Each Cooling Capacity for Single Package Heat Pumps in the 

Figure 3.2.17 Average HSPF Rating at Each Cooling Capacity for Split System Heat Pumps in 

Figure 3.2.18 Average HSPF Rating at Each Cooling Capacity for SDHV Heat Pumps in the 

in the AHRI Directory of Certified Product Performance ......................................................... 3-24
 

the AHRI Directory of Certified Product Performance ............................................................. 3-24
 

Directory of Certified Product Performance.............................................................................. 3-25
 

AHRI Directory of Certified Product Performance ................................................................... 3-26
 

the AHRI Directory of Certified Product Performance ............................................................. 3-26
 

AHRI Directory of Certified Product Performance ................................................................... 3-27
 

3-iii 
 

 

 

 

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 central air conditioners and heat pumps. It consists of two sections: the 

market assessment and the technology assessment. 

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

quantitative characterization of the residential central air conditioner and heat pump industry and 

market structure, based on publicly available information and data and information submitted by 

manufacturers and other stakeholders. Publicly available information includes 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. The technology assessment is a preliminary 

list of technologies that can improve the efficiency of residential central air conditioners and heat 

pumps. These technologies are considered in the screening analysis. 

Residential central air conditioners and heat pumps are products that are used to centrally 

heat and/or cool residential buildings. 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 conditionersa

 or packaged terminal air conditioners and heat pumps.b 

3.1.1 Definitions 

The Energy Policy and Conservation Act (EPCA) defines a “central air conditioner” as “a 

product, other than a packaged terminal air conditioner, 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. 

a

 “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 

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. b

 “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.” “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. 

3-1 
 

 

 

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

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. 

3.1.2 Product Classes 

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. 

3.1.2.1 Existing Product Classes 

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 existing 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 

3.1.2.2 Rulemaking Product Classes 

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 existc

, which is subsequent to the effective date of this rulemaking. 

Therefore, DOE did not consider those two product classes separately (instead DOE considered 

them to be space-constrained products), and examined only seven product classes for this 

residential central air conditioner and heat pump rulemaking. The seven product classes DOE 

examined are: 

c

 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. 

3-2 
• 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 

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 

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. 

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, 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. 

3-3 
3.2.1 Trade Associations 

DOE identified AHRI as the only trade group that supports, or has an interest in, the 

residential central air conditioner and heat pump industry. 

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

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

January of 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.1

 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. 

AHRI administers the ARI Performance Certified programs that test and certify the 

performance of cooling equipment. 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. 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. 

3-4 
 

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. 

**The AHRI Directory of Certified Performance did not list any space constrained products as of March 16, 2009. 

However, after January 23, 2010 (which is after the effective date for this rulemaking) the Through-the-wall 

equipment classes will expire, at which time, they will become part of the space constrained product classes. 

3.2.2 Manufacturers and Market Share 

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 3.2.2, along with their parent company in parentheses, if applicable. 

3-5 
 

 

Table 3.2.2 Manufacturer Brand Names Found in the AHRI’s Directories of Certified 

Product Performance for Residential Central Air Conditioners and Heat Pumps2 

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 3.2.1 displays the 2007 market shares for the residential central air conditioner 

market. The 7 largest residential central air conditioner and heat pump manufacturers controlled 

97 percent of the market. The seven largest manufacturers for the year 2007 are UTC/Carrier, 

Goodman, American Standard (Trane)d

, Lennox, Rheem, York and Nordyne. 

d

 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. 

3-6 
Figure 3.2.1 2007 Market Shares for Unitary Air Conditioners and Heat Pumps3 

3.2.2.1 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.4 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 residential central air conditioners and heat pumps, the 

size standard is matched to NAICS code 333415, Air-Conditioning and Warm Air Heating 

Equipment and Commercial and Industrial Refrigeration Equipment Manufacturing, which has a 

size standard of 750 employees. 

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 small business residential central air conditioner and heat pump 

manufacturers: 

• Aire-Flo 

• Airquest 

• Bard Manufacturing Company 

• Beutler Corporation 

• Heat Controller 

• Cold Point Corporation 

• Eair, LLC 

• Enviromaster International 

3-7 
 

•	 Espitech, LLC 

•	 National Coil Company 

•	 National Comfort Products 

•	 Quietside 

•	 Style Crest Products 

•	 Summit Manufacturing, Inc. 

•	 Texas Furnace, LLC 

3.2.2.2 Mergers and Acquisitions 

A trend in 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 the Amana brand. 

•	 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 

became a public company. 

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

since 1979. In 2004, Carrier Corporation acquired Linde Refrigeration. 

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

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

•	 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. 

•	 Nordyne is a subsidiary of the privately held Nortek, Inc. It introduced the Frigidaire, 

Tappan, and Philco brands as potential replacement HVAC brands in 1998. It also 

added the Gibson and Kelvinator brands in 1999. In 2002, the firm added the 

Westinghouse brand as a residential product line. The Mammoth commercial line was 

introduced as a part of Nordyne in 2003. Most recently, Nordyne added the Broan 

brand of products in 2005. 

•	 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. 

3.2.3 Regulatory Programs 

The following section details current regulatory programs mandating energy conservation 

standards for 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. 

3-8 
 

3.2.3.1 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 central air conditioners and heat 

pumps. (42 U.S.C. 6291-6309) 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 3.2.3 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 3.2.3 Current Federal Energy Conservation Standards for Residential Central Air 

Conditioners and Heat Pumpse 

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 for Region IV. 

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

3.2.3.2 Canadian Energy Conservation Standards 

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

mandates minimum energy conservation standards for residential central air conditioners and 

heat pumps. These standards apply to single package and split system air-source air conditioners 

and heat pumps with a cooling capacity less than 65,000 Btu/h. The current standards went into 

effect November 2006, and are shown in Table 3.2.4. 

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

430.32(c)(2). 

3-9 
 

 

 

 

 

Table 3.2.4 Canadian Energy Conservation Standards for Residential Central Air 

Conditioners and Heat Pumps5 

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 

*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. 

3.2.3.3 Mexican Energy Conservation Standards 

The National Commission for Energy Saving (CONAE)f is 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/hg at a 

minimum of 13 SEER.h 

Table 3.2.5 Mexican Energy Conservation Standards for Residential Central Air 

Conditioners6 

Product 

Minimum Energy 

Performance Standard 

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

3.2.4 Non-Regulatory Programs 

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

efficiency of residential central air conditioners and heat pumps. DOE reviewed two programs 

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 for residential purchasers of higherefficiency central air conditioners and heat pumps, DOE also identified Federal and State tax 

f

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

 Cooling capacity is specified in the standard as 8,800W to 19,050W.
 h

 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. 

3-10 
 

credits for residential consumers of higher-efficiency central air conditioners and heat pumps. 

DOE reviewed Federal procurement specifications for these products as well. 

3.2.4.1 Voluntary Energy Efficiency Targets 

Energy Star 

ENERGY STARi 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 Table 3.2.5. 

Table 3.2.5 ENERGY STAR Levels for Split System and Single Package Residential 

Central Air Conditioners and Heat Pumps 7 

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 

*EER is energy efficiency ratio. 

Consortium for Energy Efficiency 

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 3.2.6. 

i

 For more information, visit www.energystar.gov. 

3-11 
 

 

 

 

 

 

 

Table 3.2.6 CEE Tiers for Residential Central Air Conditioners and Heat Pumps8 

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 

3.2.4.2 Consumer Rebate Programs 

DOE has identified numerous rebate programs that are available to purchasers of new 

residential central air conditioners or heat pumps. These rebates are offered by electric utility 

companies or other agencies to residential consumers who purchase higher-efficiency units. 

Appendix 3-A provides a listing of rebates for residential central air conditioners and heat 

pumps identified by DOE. 

3.2.4.3 Consumer Tax Credits 

Federal Tax Credits 

DOE reviewed the Federal tax credit that provides consumers a credit toward their 

Federal income tax if they purchase qualifying residential central air conditioners or heat pumps. 

These tax credits apply only to products being installed in existing homes; they do not apply to 

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 air 

conditioner or heat pump, with a maximum limit of $1500. To qualify for the Federal tax credit, 

products must meet varying levels of efficiency depending on the product class. Table 3.2.7 

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

tax credit available. 

Table 3.2.7 Federal Tax Credits for Residential Central Air Conditioners and Heat Pumps9 

Product EER 

Requirement 

SEER 

Requirement 

HSPF 

Requirement 

Available Tax Credit 

Central Air Conditioners 

– Split Systems 

≥ 13.0 ≥16.0 N/A 30% of cost, up to $1,500 

Central Air Conditioners 

– Single Package 

≥12.0 ≥ 14.0 N/A 30% of cost, up to $1,500 

Air Source Heat Pumps – 

Split Systems 

≥ 12.5 ≥15.0 ≥ 8.5 30% of cost, up to $1,500 

Air Source Heat Pumps – 

Single Package 

≥ 12.0 ≥14.0 ≥8.0 30% of cost, up to $1,500 

3-12 
 

 

State Tax Credits 

DOE also identified four states that have tax credits for central air conditioners and heat 

pumps: Montana, Oregon, Indiana, and Kentucky. 

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

measures since 1998.10,11 The tax credit covers a variety of residential energy and water 

efficiency installations, including ENERGY STAR heating/cooling equipment. The amount 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.” 

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. For HVAC, residential 

appliances, and water heating, the credit is $0.40/kWh saved in the first year, or 25% of net 

purchase price, whichever is less. The credit limit for energy efficient appliances and heating 

and cooling systems is $1,000 per calendar year; excess credit may be carried forward for five 

12,13 years.

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. 

Table 3.2.8 Oregon Tax Credit for Central Air Conditioners 

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. 

3-13 
 

 

 

 

Table 3.2.9 Oregon Tax Credits for Heat Pumps 

HSPF 

EER 

12 12.5 13 

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.14,

15 

Kentucky offers a 30% 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 2009-2015 and may be carried forward for one year.16,17 

3.2.4.4 FEMP Procurement Guidelines 

DOE reviewed the Federal Energy Management Program (FEMP) procurement 

guidelines for Federal government equipment purchasing. Federal construction requirements 

include these guidelines for installing or replacing equipment. 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.18,

19 

Table 3.2.10 FEMP Performance Requirements for Residential Central Air Conditioners 

System Type SEER EER 

Split 14.5 or greater 12.0 or greater 

Packaged 14.0 or greater 11.0 or greater 

Table 3.2.11 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 

3-14 
   

     

   

3.2.5 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-K 

reports filed by publicly owned manufacturers. 

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. 

Table 3.2.12 presents the commercial air conditioning and warm air heating equipment 

manufacturing employment levels and earnings from 1997 to 2005 according to the NAICS. 

Table 3.2.12 Air Conditioning and Warm Air Heating Equipment Industry Employment 

and Payroll Data 20,21 

Year Production Workers All Employees

Payroll for All

Employees ($1000)

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

of shipments from 1997 to 2006. 

3-15 
         

       

   

       

       

       

   

       

     

           

   

 

Table 3.2.13 Air Conditioning and Warm Air Heating Equipment Industry Cost Data 10,11 

Year

Cost of Materials as a

percent of value of

shipments (percent)

Cost of Payroll for

production workers as a

percent of value of

shipments (percent)

Cost of Total Payroll

(production + admin.)

as a percent of value of

shipments (percent)

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. Fluctuations in raw material costs are common from year to year. 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. 

3.2.6 Equipment Lifetime 

The lifetime of residential 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 air-source heat pumps. Generally, most 

sources estimate the lifetime of residential 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 unitary air conditioners and heat pumps, based on input from appliance experts and 

many additional sources. 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.22 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 

3-16 
 

 

determined to be 19.0 and 16.2 years, respectively. Additional information about equipment 

lifetimes is contained in the Life-Cycle Cost and Payback Period Analysis chapter (Chapter 8) of 

this TSD. 

3.2.7 Market Performance Data 

DOE examined the AHRI Directory of Certified Product Performance for residential 

central air conditioners and heat pumps 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 

air-cooled, and therefore DOE did not examine any products that did not meet these criteria. 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. Table 3.2.14 shows 

the number of the models in the AHRI Directory of Certified Product Performance for each 

equipment class. As the table shows, the large majority of residential central air conditioners and 

heat pumps are split system products, and there are relatively few space constrained (i.e. 

through-the-wall) models. 

Table 3.2.14 Types of Models Listed in the AHRI Directory of Certified Product 

Performance 

Product Class Number of Models Listed in the AHRI 

Directory of Certified Product Performance 

Split system air conditioners 281,184 

Split system heat pumps 153,397 

Single package air conditioners 8,479 

Single package heat pumps 2,876 

Small duct, high velocity system 4,468 

Space constrained – air conditioners 12* 

Space constrained – heat pumps 12* 

*Currently there are no space constrained air conditioners or space constrained heat pumps in the AHRI Directory of 

Certified Performance. However, the AHRI Directory of Certified Performance does list through-the-wall products 

that will be classified as space constrained products prior to the effective date of this rulemaking. 

DOE examined 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 3.2.2 through Figure 3.2.6 

show histograms of the efficiency data for split system and single package central air 

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

3-17 
Figure 3.2.2 SEER Ratings for Single Package Central Air Conditioners in the AHRI 

Certified Product Performance Directory 

Figure 3.2.3 SEER Ratings for Single Package Heat Pumps in the AHRI Certified Product 

Performance Directory 

3-18 
Figure 3.2.4 SEER Ratings for Split System Central Air Conditioners in the AHRI 

Certified Product Performance Directory 

Figure 3.2.5 SEER Ratings for Split System Heat Pumps in the AHRI Directory of 

Certified Product Performance 

3-19 
 

Figure 3.2.6 SEER Ratings for SDHV Systems in the AHRI Directory of Certified Product 

Performance 

Figure 3.2.2 through Figure 3.2.6 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 12.99 SEER range. The through-the-wall products in the AHRI 

Directory of Certified Product Performance all had a SEER rating of either 10.9 (9 central air 

conditioners and 8 heat pumps were rated 10.9 SEER) or 11.0 (3 central air conditioners and 4 

heat pumps were rated 11.0 SEER). 

DOE also examined the HSPF ratings of the heat pumps in AHRI’s Directory of Certified 

Product Performance. Figure 3.2.7 through Figure 3.2.9 shows the number of single package, 

split system, and SDHV heat pumps models in the directory that fall into the specified HSPF 

bins. 

3-20 
Figure 3.2.7 HSPF Ratings for Single Package Heat Pumps in AHRI’s Directory of 

Certified Product Performance 

Figure 3.2.8 HSPF Ratings for Split System Heat Pumps in AHRI’s Directory of Certified 

Product Performance 

3-21 
Figure 3.2.9 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 7.5 to 8.49 

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

the 7.5 to 8.99 range. For SDHV heat pumps, a significant number of models fall into the range 

between 6.5 and 8.49. All 12 Through-the-wall heat pump models listed in AHRI’s directory had 

an HSPF rating of 7.1. 

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 3.2.10 through Figure 3.2.14 show the average SEER ratings at each 

equipment capacity available for single package and split system air conditioners and heat 

pumps, as well as for SDHV systems in AHRI’s Directory of Certified Product Performance. 

3-22 
Figure 3.2.10 Average SEER Ratings at Each Cooling Capacity for Single Package Air 

Conditioners in AHRI’s Directory of Certified Product Performance 

Figure 3.2.11 Average SEER Ratings at Each Cooling Capacity for Split System Air 

Conditioners in AHRI’s Directory of Certified Product Performance 

3-23 
 Figure 3.2.12 Average SEER Rating at Each Cooling Capacity for Single Package Heat 

Pumps in the AHRI Directory of Certified Product Performance 

Figure 3.2.13 Average SEER Rating at Each Cooling Capacity for Split System Heat 

Pumps in the AHRI Directory of Certified Product Performance 

3-24 
Figure 3.2.14 Average SEER Rating at Each Cooling Capacity for SDHV Systems 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 two and three ton cooling capacities (i.e. 24,000 and 36,000 Btu/h cooling 

capacities) where a greater range of average efficiencies occurs, and where the highest average 

SEER ratings occur. SDHV systems appear to have an average SEER value in the range of 11 to 

13 SEER for the entire range of 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 3.2.15 through Figure 

3.2.17 show the average HSPF at each available capacity rating in AHRI’s directory for single 

package, split system, and SDHV heat pumps. 

3-25 
Figure 3.2.15 Average HSPF at Each Cooling Capacity for Single Package Heat Pumps in 

the AHRI Directory of Certified Product Performance 

Figure 3.2.16 Average HSPF Rating at Each Cooling Capacity for Split System Heat 

Pumps in the AHRI Directory of Certified Product Performance 

3-26 
 

Figure 3.2.17 Average HSPF Rating at Each Cooling Capacity for SDHV 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. 

3.2.8 Historical Shipments and Efficiencies 

3.2.8.1 Historical Shipments 

The Air-Conditioning, Heating, and Refrigeration Institute (AHRI) provided historical 

shipments data over the 1990-2007 time-period disaggregated into the four primary product 

classes.23 Historical shipments from 1972-1989 were also provided by AHRI from previous 

data submittals to the Lawrence Berkeley National Laboratory (LBNL).24 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 1990-2007 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. Table 3.2.14 

summarizes the historical shipments data. 

3-27 
Table 3.2.15 Central Air Conditioner and Heat Pump Shipments 

Year 

Split CAC 

thousands 

Single Package CAC 

thousands 

Split HP 

thousands 

Single Package HP 

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 

Source: Air-Conditioning, Heating, and Refrigeration Institute (AHRI) 

3.2.8.2 Historical Efficiencies 

AHRI provided historical shipment-weighted efficiency data (SWEF) data spanning the 

years 1992 to 2008.28 Between 1992, the year in which the first set of standards for central air 

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 3.2.18 shows the SWEFs for split system and single package central air 

3-28 
 

conditioners. The figure also presents the linear fit to each product class’ SWEF data series. 

The linear fits have high coefficients of determination, i.e., linear fits provide a good estimate of 

the SWEF growth rate. Table 3.2.15 provides a summary of the SWEF growth rates for each 

product class. 

Split A/C 

SEER = 0.0703 * year - 129.65 

R2 = 0.9633 

Package A/C 

SEER = 0.0778 * year - 144.78 

R2 = 0.9455 

10.0 

10.2 

10.4 

10.6 

10.8 

11.0 

11.2 

11.4 

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 

Year 

Shipment-Weighted SEER 

Split A/C 

Package A/C 

Linear (Split A/C) 

Linear (Package A/C) 

Source: Air-Conditioning, Heating, and Refrigeration Institute (AHRI) 

Figure 3.2.18 Central Air Conditioner Historical Shipment-Weighted Efficiencies with 

Linear Fits 

Table 3.2.16 Central Air Conditioner Shipment-Weighted Efficiency Growth Rates 

SWEF Growth Rate 

Product Class SEER increase per year 

Split System Air Conditioners 0.0703 

Single Package Air Conditioners 0.0778 

For heat pumps, between 1992 and 2006, the SEER-based also grew by approximately 

one SEER point. Figure 3.2.19 shows the SEER-based SWEFs for split system and single 

package heat pumps. The figure also presents the linear fit to each product class’ SWEF data 

series. The linear fits have high coefficients of determination, i.e., linear fits provide a good 

estimate of the SWEF growth rate. Table 3.2.16 provides a summary of the SEER-based SWEF 

growth rates for each product class. AHRI did not provide historical SWEF data for heat pump 

HSPFs. 

3-29 
 

Split HP 

SEER = 0.0739 * year - 136.55 

R2 = 0.9594 

Package HP 

SEER = 0.0736 * year - 136.03 

R2 = 0.8886 

10.2 

10.4 

10.6 

10.8 

11.0 

11.2 

11.4 

11.6 

11.8 

1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 

Year 

Shipment-Weighted SEER 

Split HP 

Package HP 

Linear (Split HP) 

Linear (Package HP) 

Source: Air-Conditioning, Heating, and Refrigeration Institute (AHRI) 

Figure 3.2.19 Heat Pump Historical Shipment-Weighted Efficiencies base on SEER with 

Linear Fits 

Table 3.2.17 Heat Pump Shipment-Weighted Efficiency Growth Rates 

SWEF Growth Rate 

Product Class SEER increase per year 

Split System Heat Pumps 0.0739 

Single Package Heat Pumps 0.0736 

3.2.9 Saturations in U.S. Households 

Saturation refers to the percentage of the housing stock with a given product. The 

American Housing Survey (AHS) provides historical stock saturations for central air 

conditioning and heat pump equipment for every other year between 1991−2007.25 Table 3.2.17 

summarizes the saturations for central air conditioners, heat pump, and both types of equipment. 

Central air conditioerns and heat pump saturation has grown from 38.6 percent to 64.6 percent 

from 1991 to 2007. 

3-30 
 

Table 3.2.18 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 TECHNOLOGY ASSESSMENT 

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. 

3.3.1 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. 

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. Variable-speed 

compressors reduce energy consumption in three ways (but it should be noted that it typically 

increases efficiency over a broad operating range but does not inherently increase maximum 

efficiency at the compressor rating point): 

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. 

Temperature drops decrease, resulting in reduced pressure rise across the compressor, 

which also improves efficiency. 

2.	 Close matching of load eliminates the cycling that occurs with single-stage compressors. 

Maintaining a constant pressure is more efficient because losses at higher pressure rise 

are greater than gains at lower pressure rise. 

3-31 
 

3.	 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. 

3.3.2 Fan System Improvements 

3.3.2.1 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 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. 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. This makes PSC motors more energy efficient, with motor efficiencies 

ranging from 50 to 70 percent. PSC motors are produced in large quantities and are relatively 

inexpensive. 

Another type of electric motor, the brushless direct current (DC) (i.e., electronicallycommutated motor (ECM), is more energy-efficient than PSC motors of comparable size and 

capacity. Brushless DC motors, which are sold in high volumes, are three-phase electric motors 

with efficiencies ranging from 70 to 80 percent. However, brushless DC motors can weigh twice 

as much as equivalent PSC motors. In addition, brushless DC motors are complex, and can cost 

from two and a half to five times as much as a PSC motor. 

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 

3-32 
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. 

3.3.2.2 Fan Motor Controllers 

Fan motor controllers allow fan motors to run at variable speed to match changing load 

conditions. During periods of frost build-up in heat pumps, fan motor power requirements 

increase; during the post-defrost period, power requirements decrease. Matching the fan speed to 

all conditions ensures more stable discharge air temperatures and improves coil performance. 

Fan motor controllers would also allow both central air conditioners and heat pumps run more 

efficiently at varying ambient humidity and temperature levels. Because of practical limitations 

on efficiency, variable speed systems dominate the market over 14 SEER, and it is unusual to 

find a system over 13 SEER that does not incorporate a variable speed indoor blower. 

3.3.2.3 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, and may 

not 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. 

3.3.3 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 

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. 

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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. 

3.3.4 Heat Exchanger Technologies and Improvements 

3.3.4.1 Baseline Technology 

Most 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. Increasing the area of the 

coil decreases the necessary temperature difference and therefore decreases the required 

saturated evaporator temperature. This results in an increased compressor energy efficiency ratio 

(EER) and lower compressor energy consumption. 

The condenser coil is responsible for condensing and sub-cooling the entering refrigerant 

vapor while rejecting heat from the refrigerant to the ambient air. As with evaporator coils, 

increasing the area of the condenser coil will decrease the necessary change in temperature 

across the coil, resulting in increased compressor efficiency (increased EER). 

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 

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. 

3.3.4.2 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. However, many applications limit the 

amount of coil size increase in order to maintain overall cabinet dimensions. Most approaches to 

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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. 

3.3.4.3 Alternative Coil Technologies 

3.3.4.4.1. Liquid Suction Heat Exchangers 

The goal 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 super-heating 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. 

3.3.4.4.2 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 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. Because the microchannel fin arrangement prevents natural condensate drainage, their 

use in heat pump and evaporator coil applications is not forthcoming. 

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 

3-35 
 

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 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. 

3.3.4.4.3 Flat-Tube Heat Exchangers 

Flat-tube, louver-fin heat exchangers offer various advantages over traditional roundtube, 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 exchanger. The significant 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. 

3-36 
 

 

3.3.5 Designs Relevant Only to Heat Pumps 

The following technologies, defrost mechanism and defrost cycle control, are two 

examples of defrost-related improvements applicable to heat pump designs, and it should be 

noted that they are not intended to comprise an exhaustive list of viable technologies. 

3.3.5.1 Defrost Mechanism 

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. 

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 

defrosting 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. 

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 conduit 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 

3-37 
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. A refrigerant-towater heat exchanger is used to provide energy to the refrigerant and allow it to melt the frost on 

the outdoor coil. This can be done without any degradation to heat pump performance, and 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. 

3.3.5.2 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 the 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. 

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