1 

Investigation of the Relationship between IEER and EER for 

Commercial Air-cooled Air Conditioners and Air-source Heat Pumps with 

Rated Cooling Capacities Greater than or Equal to 65,000 Btu/h and Less than 760,000 Btu/h 

January 25, 2013 

Executive Summary

This document provides the methodology for, and the results of, the investigation of the 

relationship between Integrated Energy Efficiency Ratio (IEER) and Energy Efficiency Ratio 

(EER) for the purpose of evaluating the relationship between the current Federal minimum 

standards in EER and baseline IEER values for commercial, air-cooled air conditioners (AC) and 

heat pumps (HP) with rated cooling capacities greater than and equal to 65,000 British thermal 

units per hour (Btu/hr) and less than 760,000 Btu/hr (i.e., 5 to 63 tons). 

For the analysis shown in Table E.1., DOE considered only those models that are rated at the 

current Federal minimum energy conservation standard level by equipment class. DOE then 

analyzed the distribution of corresponding IEER values based on manufacturer ratings for each 

of the six equipment classes and two heating-types. Table E.1. summarizes various IEER 

baseline values and the current COP Federal minimum energy conservation standards for each 

heat pump equipment class. Additional details about the methodology and analysis is described 

in detail below. 

Table E.1. IEERs at various cut-offs 

Equipment 

Class

Class 1: AC

≥ 65 to < 135 

kBTU/h

Class 2: AC

≥ 135 to < 240 

kBTU/h

Class 3: AC

≥ 240 to < 760 

kBTU/h

Class 4: HP

≥ 65 to < 135 

kBTU/h

Class 5: HP

≥ 135 to < 240 

kBTU/h

Class 6: HP

≥ 240 to < 760 

kBTU/h‡

Supplemental 

heating-type

Electric 

resistance 

heating/no 

heating

Other 

heating

†

Electric 

resistance 

heating/no 

heating

Other 

heating

†

Electric 

resistance 

heating/no 

heating†

Other 

heating

†

Electric 

resistance 

heating/no 

heating

Other 

heating

**

Electric 

resistance 

heating/no 

heating†

Other 

heating

†**

Electric 

resistance 

heating/no 

heating

Other 

heating

**

IEER Cut-offs

Min 11.2 11.2 10.8 10.8 10.1 9.9 11.0 10.8 10.7 10.5 9.5 9.3

10% 11.4 11.2 11.1 10.8 10.1 9.9 11.3 11.1 10.7 10.5 9.5 9.3

25% 11.7 11.2 11.2 10.8 10.5 9.9 11.5 11.3 10.7 10.5 9.5 9.3

50% 12.2 11.2 11.8 10.8 11.9 9.9 11.8 11.6 11.0 10.8 9.5 9.3

Mean 12.4 11.4 11.9 11.1 11.4 10.1 12.0 11.8 11.2 11.0 9.5 9.3

Max 20.8 20.2 18.7 18.4 18.7 14.3 20.2 20.2 18.4 18.2 9.5 9.3

EER* 11.2 11.0 11.0 10.8 10.0 9.8 11.0 10.8 10.6 10.4 9.5 9.3

IEER#

11.4 11.2 11.2 11.0 10.1 9.9 11.2 11.0 10.7 10.5 9.6 9.4

COP (47°F)* - - - 3.3 3.2 3.2

* Current Federal energy conservation standard (10 CFR Part 431.97). 

#

 Efficiency levels in ANSI/ASHRAE Standard 90.1-2010. 

** Italicized values realize a 0.2 Btu/W-h credit given to heat pumps with no supplemental electric resistance heating. 

†Data overlap prevents the identification of different IEER values for the 10% and 25% cut-offs. 

‡ Cut-offs based on the efficiency levels in ANSI/ASHRAE Standard 90.1-2010 were used due to insufficient data for this class in the AHRI 

Database. 
2 

Purpose 

This document provides the methodology and results of DOE’s investigation of the relationship 

between IEER and EER of current equipment available on the market for commercial, air-cooled 

ACs and HPs with rated cooling capacities greater than or equal to 65,000 Btu/hr and less than 

760,000 Btu/hr (i.e., 5 and 63 tons). This analysis also examines the impact of such a relationship 

on current product models. 

Methodology 

The methodology consisted of a search on the Air-Conditioning, Heating, and Refrigeration 

Institute (AHRI) Certification Database with the following constraints: 

• Commercial,

• Air-cooled, 

• AC or HP, and

• ≥ 65 to < 760 kBTU/h. 

Individual model data for equipment meeting the above criteria was downloaded from the AHRI 

Certification Database on August 20, 2012. DOE further narrowed the sample by only 

considering models that: 

• Have “Active Status” in the AHRI Certification Database, and 

• Have capacity, EER, and IEER ratings corresponding to a line-to-line voltage of 208 V 

(120 V line-to-neutral, for U.S. products). 

Data was separated into six equipment classes consistent with the equipment classes reflected by 

the current Federal energy conservation standards in Title 10 of the Code of Federal Regulations 

Section 431.97: 

• Class 1: AC ≥ 65 to < 135 kBTU/h; 

• Class 2: AC ≥ 135 to < 240 kBTU/h; 

• Class 3: AC ≥ 240 to < 760 kBTU/h; 

• Class 4: HP ≥ 65 to < 135 kBTU/h; 

• Class 5: HP ≥ 135 to < 240 kBTU/h; and 

• Class 6: HP ≥ 240 to < 760 kBTU/h. 

Figure 1 shows a scatter plot of the resulting data. DOE removed any models from consideration 

that were showing efficiency ratings below the Federal energy conservation standards. After 

removal of the outliers, the final data set contained 6600 product models. 
3 

Figure 1. A Scatter Plot of the IEER and EER Data for Equipment Class 1 

The current Federal energy conservation standards for commercial, air-cooled AC and HP 

equipment are also differentiated based on the type of heating associated with the unit. 

Specifically, the heating-types are differentiated by their heating energy source for air 

conditioners (or their supplemental heating energy source for heat pumps). The “Electric 

resistance heating/no heating” category consists of air conditioning (heat pump) equipment that 

have (supplemental) electric resistance heating or no (supplemental) heating, whereas the “Other 

heating” category consists of air conditioning (heat pump) equipment that have (supplemental) 

hydronic heating or (supplemental) heating via combustion of natural gas. 

While the AHRI Certification Database does not specify the heating-type, the California Energy 

Commission’s (CEC) Database does. Therefore, the two databases were cross-referenced to 

determine the heating-type for the models listed in the AHRI Certification Database. However, 

examining the data for the heat pump equipment classes revealed that only two product models 

have a heating-type of “Other heating.” Being such a small sample size, the data set pertaining to 

heat pumps was not disaggregated by heating-type and those product models with a heating-type 

of “other heating” were not included in any datasets. 

The dataset for each equipment class was split into two groups based on whether the units were 

baseline equipment or non-baseline equipment. Baseline equipment groups are defined as 

equipment rated at the current Federal minimum energy conservation standards. In Figure 2 

(presented at the end of this document), data from the non-baseline equipment group are 

exhibited in a scatter plot (with each data point represented by a solid circle), while data for the 

baseline equipment group are plotted in a vertical line (with each data point represented by an 

‘x’).

DOE then calculated various statistics on the dataset including the minimum, mean, and 

maximum IEER levels. In addition, DOE established IEER bins for each equipment class and 

heating type. The bins represent the IEER value that eliminates a given percentage of the models 

that have an EER equal to the DOE minimum efficiency standard. The minimum (0%), median 

(50%), mean, and maximum IEER value, as well as the IEER values that eliminate 10% and 25% 

of the market were determined, depending on data availability, and plotted in Figure 2. 
4 

For each cut-off in equipment classes 4, 5, and 6 with the “Other heating” heating-type, the 

IEERs were estimated using a 0.2 Btu/W-h credit given to heat pumps with no supplemental 

electric resistance heating because of the lack of commercially available data. Similarly, since 

limited data were available in the AHRI Certification Database for equipment class 6 and 

overlapped to make up only three points on the scatter plot, the IEER cut-offs for this class could 

not be determined; instead the IEER cut-offs were based on the IEER efficiency levels in

ANSI/ASHRAE Standard 90.1-2010. 

Table 1. IEERs at Various Cut-offs 

Equipment 

Class

Class 1: AC

≥ 65 to < 135 

kBTU/h

Class 2: AC

≥ 135 to < 240 

kBTU/h

Class 3: AC

≥ 240 to < 760 

kBTU/h

Class 4: HP

≥ 65 to < 135 

kBTU/h

Class 5: HP

≥ 135 to < 240 

kBTU/h

Class 6: HP

≥ 240 to < 760 

kBTU/h‡

Supplemental 

heating-type

Electric 

resistance 

heating/no 

heating

Other 

heating

†

Electric 

resistance 

heating/no 

heating

Other 

heating

†

Electric 

resistance 

heating/no 

heating†

Other 

heating

†

Electric 

resistance 

heating/no 

heating

Other 

heating

**

Electric 

resistance 

heating/no 

heating†

Other 

heating

†**

Electric 

resistance 

heating/no 

heating

Other 

heating

**

IEER Cut-offs

Min 11.2 11.2 10.8 10.8 10.1 9.9 11.0 10.8 10.7 10.5 9.5 9.3

10% 11.4 11.2 11.1 10.8 10.1 9.9 11.3 11.1 10.7 10.5 9.5 9.3

25% 11.7 11.2 11.2 10.8 10.5 9.9 11.5 11.3 10.7 10.5 9.5 9.3

50% 12.2 11.2 11.8 10.8 11.9 9.9 11.8 11.6 11.0 10.8 9.5 9.3

Mean 12.4 11.4 11.9 11.1 11.4 10.1 12.0 11.8 11.2 11.0 9.5 9.3

Max 20.8 20.2 18.7 18.4 18.7 14.3 20.2 20.2 18.4 18.2 9.5 9.3

EER* 11.2 11.0 11.0 10.8 10.0 9.8 11.0 10.8 10.6 10.4 9.5 9.3

IEER#

11.4 11.2 11.2 11.0 10.1 9.9 11.2 11.0 10.7 10.5 9.6 9.4

COP (47°F)* - - - 3.3 3.2 3.2

* Current Federal energy conservation standard (10 CFR Part 431.97). 

#

 Efficiency levels in ANSI/ASHRAE Standard 90.1-2010. 

** Italicized values realize a 0.2 Btu/W-h credit given to heat pumps with no supplemental electric resistance heating. 

†Data overlap prevents the identification of different IEER values for the 10% and 25% cut-offs. 

‡ Cut-offs based on the efficiency levels in ANSI/ASHRAE Standard 90.1-2010 were used due to insufficient data for this class in the AHRI 

Database. 
5 

Figure 2. Scatter plots for Equipment Class 1: AC ≥ 65 to < 135 kBtu/h, Electric Heat/No

Heating with Cut-off Lines (Dotted)

Figure 3. Scatter Plots for Equipment Class 1: AC ≥ 65 to < 135 kBtu/h, Other Heating 

with Cut-off Lines (Dotted) 

8

10

12

14

16

18

20

22

8 9 10 11 12 13 14 15 16

IEER

EER

Mean: 53% cut-off

50% cut-off

25% cut-off

10% cut-off

Minimum

8

10

12

14

16

18

20

22

8 9 10 11 12 13 14 15 16

IEER

EER

Mean: 65% cut-off

Minimum
6 

Figure 4. Scatter Plots for Equipment Class 2: AC ≥ 135 to < 240 kBtu/h, Electric Heat/No 

Heating with Cut-off Lines (Dotted) 

Figure 5. Scatter Plots for Equipment Class 2: AC ≥ 135 to < 240 kBtu/h, Other Heating

Cut-off Lines (Dotted) 

8

10

12

14

16

18

20

22

8 9 10 11 12 13 14 15 16

IEER

EER

Mean: 52% cut-off

50% cut-off

25% cut-off

10% cut-off

Minimum

8

10

12

14

16

18

20

22

8 9 10 11 12 13 14 15 16

IEER

EER

Mean: 80% cut-off

Minimum
7 

Figure 6. Scatter Plots for Equipment Class 3: AC ≥ 240 to < 760 kBtu/h, Electric Heat/No 

Heating with Cut-off Lines (Dotted) 

Figure 7. Scatter Plots for Equipment Class 3: AC ≥ 240 to < 760 kBtu/h, Other Heating

with Cut-off Lines (Dotted)

8

10

12

14

16

18

20

22

8 9 10 11 12 13 14 15 16

IEER

EER

50% cut-off

Mean: 41% cut-off

25% cut-off

Minimum

8

10

12

14

16

18

20

22

8 9 10 11 12 13 14 15 16

IEER

EER

Mean: 82% cut-off

Minimum
8 

Figure 8. Scatter Plots for Equipment Class 4: HP ≥ 65 to < 135 kBtu/h, Electric Heat/No 

Heating with Cut-off Lines (Dotted)

Figure 9. Scatter Plots for Equipment Class 5: HP ≥ 135 to < 240kBtu/h, Electric Heat/No 

Heating with Cut-off Lines (Dotted)

8

10

12

14

16

18

20

22

9 10 11 12 13 14

IEER

EER

Mean

50% cut-off

25% cut-off

10% cut-off

Minimum

8

10

12

14

16

18

20

22

9 10 11 12 13 14

IEER

EER

Mean: 75% cut-off

50% cut-off

Minimum
9 

Figure 10. Scatter Plots for Equipment Class 6: HP ≥ 240 to < 760 kBtu/h, Electric Heat/No 

Heating with Cut-off Lines (Dotted)

8

10

12

14

16

18

20

22

9 10 11 12 13 14

IEER

EER