i

CHAPTER 5. ENGINEERING ANALYSIS

TABLE OF CONTENTS

5.1 INTRODUCTION .............................................................................................................. 1

5.2 EQUIPMENT CLASSES AND REPRESENTATIVE UNITS ANALYZED................... 2

5.2.1 Electric Motor Design Type.................................................................................... 2

5.2.2 Horsepower Rating ................................................................................................. 3

5.2.3 Pole-Configuration.................................................................................................. 4

5.2.4 Enclosure Type ....................................................................................................... 5

5.2.5 Equipment Class Group 1 (NEMA Design A and B Electric Motors)................... 7

5.2.6 Equipment Class Group 2 (NEMA Design C Electric Motors).............................. 7

5.2.7 Equipment Class Group 3 (Fire Pump Electric Motors)......................................... 8

5.3 BASELINE AND CANDIDATE STANDARD LEVELS OF EFFICIENCY .................. 8

5.3.1 Candidate Standard Levels of Efficiency ............................................................... 9

5.4 ENGINEERING ANALYSIS METHODOLOGY........................................................... 11

5.4.1 Subcontractor Tear-downs.................................................................................... 12

5.4.2 Subcontractor Software Designs........................................................................... 12

5.5 COST MODEL................................................................................................................. 14

5.5.1 Constructing a Bill of Materials............................................................................ 16

5.5.2 Labor Costs and Assumptions .............................................................................. 17

5.5.3 Manufacturer Markups.......................................................................................... 17

5.6 RESULTS OF ENGINEERING ANALYSIS .................................................................. 18

5.6.1 NEMA Design B, 5-Horsepower, 4-Pole, Enclosed Electric Motor .................... 18

5.6.2 NEMA Design B, 30-Horsepower, 4-Pole, Enclosed Electric Motor .................. 21

5.6.3 NEMA Design B, 75-Horsepower, 4-Pole, Enclosed Electric Motor .................. 23

5.6.4 NEMA Design C, 5-Horsepower, 4-Pole, Enclosed Electric Motor .................... 26

5.6.5 NEMA Design C, 50-Horsepower, 4-Pole, Enclosed Electric Motor .................. 28

5.7 SCALING METHODOLOGY ......................................................................................... 30

5.7.1 Scaling Approach Using Incremental Improvements of Motor Losses................ 30

5.7.2 Scaling Approach Using Regression Equations ................................................... 33
ii

LIST OF TABLES

Table 5.1 Electric Motor Equipment Class Groups................................................................ 2

Table 5.2 Design Characteristics of the Five Representative Units Analyzed ....................... 7

Table 5.3 Baseline Efficiency Ratings of Representative Units............................................. 8

Table 5.4 Candidate Standard Levels ................................................................................... 10

Table 5.5 Candidate Standard Levels for each Representative Unit..................................... 11

Table 5.6 Stack Length and C Dimension Measurements of Torn Down and Modeled

Motors 14

Table 5.7 Labor Markups for Electric Motor Manufacturers ............................................... 17

Table 5.8 Efficiency and Manufacturer Selling Price Data for the NEMA Design B,......... 20

Table 5.9 NEMA Design B, 5-Horsepower, 4-Pole, Enclosed Motor Characteristics......... 20

Table 5.10 NEMA Design B, 5-Horsepower, 4-Pole, Enclosed Motor Modeled 

Characteristics21

Table 5.11 30-Horsepower CSL 2 and CSL 3 Testing and Tear-down Results..................... 21

Table 5.12 Efficiency and Manufacturer Selling Price Data for the NEMA Design B, 30-

Horsepower Motor........................................................................................................................ 23

Table 5.13 NEMA Design B, 30-Horsepower, 4-Pole, Enclosed Motor Characteristics....... 23

Table 5.14 NEMA Design B, 30-Horsepower, 4-Pole, Enclosed Motor Modeled 

Characteristics23

Table 5.15 Efficiency and Manufacturer Selling Price Data for the NEMA Design B, 75-

Horsepower Motor........................................................................................................................ 25

Table 5.16 NEMA Design B, 75-Horsepower, 4-Pole, Enclosed Motor Characteristics....... 25

Table 5.17 NEMA Design B, 75-Horsepower, 4-Pole, Enclosed Motor Modeled 

Characteristics26

Table 5.18 Efficiency and Manufacturer Selling Price Data for the NEMA Design C, 5-

Horsepower Motor........................................................................................................................ 27

Table 5.19 NEMA Design C, 5-Horsepower, 4-Pole, Enclosed Motor Characteristics......... 28

Table 5.20 NEMA Design C, 5-Horsepower, 4-Pole, Enclosed Motor Modeled 

Characteristics28

Table 5.21 Efficiency and Manufacturer Selling Price Data for the NEMA Design C, 50-

Horsepower Motor........................................................................................................................ 29

Table 5.22 NEMA Design C, 50-Horsepower, 4-Pole, Enclosed Motor Characteristics....... 30

Table 5.23 NEMA Design C, 50-Horsepower, 4-Pole, Enclosed Motor Modeled 

Characteristics30

LIST OF FIGURES

Figure 5.1 Electric Motor Shipments by Design Type for 2011.............................................. 3

Figure 5.2 Electric Motors Shipments by Horsepower Rating for 2011.................................. 4

Figure 5.3 Electric Motor Shipments by Pole Configuration for 2011.................................... 5

Figure 5.4 Electric Motor Shipments by Enclosure Type for 2011 ......................................... 6

Figure 5.5 Standard Method of Cost Accounting for Standards Rulemaking........................ 15

Figure 5.6 NEMA Design B, 5-Horsepower, 4-Pole, Enclosed Electric Motor Engineering 

Analysis Curve.............................................................................................................................. 19

Figure 5.7 NEMA Design B, 30-Horsepower, 4-Pole, Enclosed Electric Motor Engineering 

Analysis Curve.............................................................................................................................. 22

Figure 5.8 NEMA Design B, 75-Horsepower, 4-Pole, Enclosed Motor Engineering Analysis 

Curve 24

Figure 5.9 NEMA Design C, 5-Horsepower, 4-Pole, Enclosed Motor Engineering Analysis 

Curve 27

Figure 5.10 NEMA Design C, 50-Horsepower, 4-Pole, Enclosed Motor Engineering Analysis 

Curve 29

Figure 5.11 Segmentation of Electric Motor Market for Representative Units....................... 32

Figure 5.12 NEMA Premium Motor Losses versus Horsepower Rating................................. 34

Figure 5.13 Function of Electric Motor Losses with Horsepower for 4-Pole, Enclosed Electric 

Motors 35

Figure 5.14 Function of Electric Motor Losses with Horsepower Derived for CSL 2 and CSL 

3 for 4-Pole, Enclosed Electric Motors of NEMA Design A & B................................................ 36

Figure 5.15 Scaling Across Electric Motor Configurations..................................................... 37
iii

LIST OF ACRONYMS AND ABBREVIATIONS

A ampere

AC alternating current

AWG American wire gauge

BOM bill of materials

CSL candidate standard level

DOE United States Department of Energy

EISA Energy Independence and Security Act of 2007

IEC International Electrotechnical Commission

in inch

lbs pounds

M* M15, M19, M36, M47, M56 - grade of core steel

MSP manufacturer selling price

Nm Newton meter 

NCI Navigant Consulting, Inc.

NEMA National Electrical Manufacturers Association

NIA national impact analysis

RPM revolutions per minute

SEC Securities and Exchange Commission

SME subject matter expert

TSD technical support document

U.S. United States

V volt
1

CHAPTER 5. SCREENING ANALYSIS

5.1 INTRODUCTION

The engineering analysis estimates the increase in manufacturer selling price (MSP) 

associated with technological design changes that improve the efficiency of an electric motor. 

This chapter presents the U.S. Department of Energy’s (DOE’s) assumptions, methodology and 

findings for the electric motor engineering analysis. The output from the engineering analysis is 

a “cost-efficiency” relationship for each electric motor analyzed which describes how its cost 

changes as efficiency increases. The output of the engineering analysis is used as an input to the 

life-cycle cost analysis (preliminary Technical Support Document (preliminary TSD) chapter 8) 

and the national impact analysis (preliminary TSD chapter 10).

The engineering analysis takes input from the market and technology assessment (see 

preliminary TSD chapter 3) and the screening analysis (see preliminary TSD chapter 4). These 

inputs include equipment classes, baseline electric motor performance, methods for improving 

efficiency, and design options that have passed the screening criteria. The engineering analysis 

uses these inputs, coupled with material price estimates, design parameters, and other 

manufacturer inputs to develop the relationship between the MSP and nominal full-load 

efficiency of the representative electric motors studied.

At its most basic level, the output of the engineering analysis is a curve that estimates the 

MSP for a range of efficiency values. This output is subsequently marked-up to determine the 

end-user prices based on the various distribution channels (see preliminary TSD chapter 6). After 

determining customer prices by applying distribution chain markups, sales tax, and contractor 

markups, the data is combined with the energy-use and end-use load characterization (see 

preliminary TSD chapter 7) and used as a critical input to the customer’s life-cycle cost and 

payback period analysis (see preliminary TSD chapter 8).

The results presented in this chapter do not provide a full assessment of a manufacturer’s 

costs associated with increasing efficiency levels for an electric motor. The relationship 

presented in this chapter assumes an ideal situation, where the manufacturer does not incur any 

costs associated with retooling, product redesign, training, or marketing associated with 

incorporating design changes to its equipment lines to achieve the efficiency levels presented. In 

the notice of proposed rulemaking stage of the rulemaking, DOE will attempt to quantify the 

additional costs that the manufacturer would incur when complying with mandatory efficiency 

standards. For discussion of these costs and DOE’s methodology for quantifying them, see 

preliminary TSD chapter 12, the preliminary manufacturer impact analysis.

In this chapter, DOE discusses the equipment classes analyzed and the representative 

electric motors selected from all motors considered for energy conservation standards. As 

discussed in chapters 2 and 3 of this TSD, the electric motors in the scope of coverage of this 

rulemaking include single-speed, squirrel-cage induction, alternating current (AC), polyphase 

motors from 1 to 500 horsepower and National Electrical Manufacturers Association (NEMA) 

Design A, B, and C electric motors, including fire pump electric motors. The engineering
2

analysis selected three NEMA Design B electric motors to analyze the NEMA Design A and B 

equipment class group and two NEMA Design C electric motors to analyze the NEMA Design C 

equipment class group. The fire pump electric motor equipment class group will be based on the 

three NEMA Design B electric motors. DOE also presents the methodology, inputs, and results 

associated with the development of MSP versus efficiency curves for each of the representative 

electric motors. Finally, DOE discusses the approach used to scale the engineering analysis to all 

other equipment classes for the national impact analysis.

5.2 EQUIPMENT CLASSES AND REPRESENTATIVE UNITS ANALYZED

Due to the large number of equipment classes, DOE did not directly analyze all covered 

electric motors. Instead, DOE selected certain equipment classes to directly analyze after 

reviewing electric motors shipments, examining manufacturers’ catalog data, and soliciting 

feedback from interested parties. The equipment classes that DOE directly analyzes and focuses 

its engineering analysis on are referred to as representative units. Table 5.1 shows the equipment 

class groups discussed in preliminary TSD chapter 3 and the corresponding electric motor 

designs they encompass. As mentioned above, DOE selected three representative units to 

analyze in equipment class group 1 and two representative units in equipment class group 2. For 

equipment class group 3, DOE plans on developing any potential amended energy conservation 

standards based off of its analysis of equipment class group 1 because fire pump electric motors 

are required to meet National Electrical Manufacturers Association (NEMA) Design B 

performance standards.

Table 5.1 Electric Motor Equipment Class Groups

Equipment 

Class Group

Electric Motor

Design Type 

Horsepower

Rating

Pole

Configuration Enclosure

1 NEMA Design A & B* 1-500 2, 4, 6, 8 Open

Closed

2 NEMA Design C* 1-200 2, 4, 6, 8 Open

Closed

3 Fire Pump* 1-500 2, 4, 6, 8

Open

Closed

*Includes International Electrotechnical Commission (IEC) equivalent design types.

DOE considered each of the characteristics listed in Table 5.1when selecting its 

representative units. The sections that follow describe the decisions that DOE made with respect 

to each of these electric motor characteristics.

5.2.1 Electric Motor Design Type

For equipment class group 1 that includes NEMA Design A and B electric motors, DOE 

only selected NEMA Design B motors as representative units to analyze in the engineering 

analysis. DOE chose NEMA Design B electric motors because NEMA Design A electric motors 

can generally meet NEMA Design B efficiency levels due to their less stringent locked-rotor 
3

current limits. In other words, NEMA Design B motors slightly limit the incremental increase in 

energy conservation standards that could be technologically feasible. However, by directly 

analyzing NEMA Design B motors, it ensures that any potential amendments to the current 

energy conservation standards could be met by all motors covered in equipment class group 1.

Additionally, NEMA Design B units have much higher shipment volumes than NEMA Design A 

motors. Figure 5.1 shows the relative shipments of each electric motor design type, which 

demonstrates that NEMA Design B motors constitute the vast majority of all shipments with a 

market share of 98.7 percent. Finally, by choosing NEMA Design B motors, DOE could also 

apply the results of its equipment class group 1 analysis to its equipment class group 3 analysis 

because fire pump motor designs are held to very similar design constraints as NEMA Design B 

motors. 

For equipment class group 2, DOE selected two representative units to analyze directly. 

Because Design C is the only NEMA design type covered by this equipment class group, DOE 

only selected NEMA Design C motors for analysis as its representative units.

Figure 5.1 Electric Motor Shipments by Design Type for 2011

5.2.2 Horsepower Rating

Horsepower rating is an important equipment class setting criterion, which DOE received 

multiple comments about when developing its representative units. When DOE selected its 

preliminary analysis representative units, DOE chose those horsepower ratings that constitute a 

high volume of shipments in the market and provide a sufficiently wide range upon which DOE 

could reasonably base a scaling methodology. For NEMA Design B motors, for example, DOE 

chose 5-, 30-, and 75-horsepower-rated electric motors to analyze as representative units. DOE 

selected the 5-horsepower rating because it is the rating with the highest shipment volume of the

electric motors considered. Figure 5.2 shows shipments of electric motors broken down by 

horsepower rating and demonstrates that the 5-horsepower rating constituted nearly 15 percent of 

shipments in 2011. DOE selected the 30-horsepower rating as an intermediary between the 
4

small and large frame number series electric motors. For the largest frame number series, DOE 

elected to analyze a 75-horsepower rated electric motor. DOE believes that this rating is an 

appropriate choice to represent the highest horsepower ratings because there tends to be minimal 

change in efficiency at the highest horsepower ratings. For consecutive horsepower ratings 

above 75, the nominal efficiencies that motors must meet in order to be deemed NEMA Premium 

tend to repeat.

For NEMA Design C electric motors, DOE only selected two horsepower ratings because 

of the relatively low shipment volumes. As with NEMA Design B motors, DOE elected to 

analyze the 5-horsepower rating because of its relatively high market share. For an upper bound, 

DOE selected the 50-horsepower rating.

Figure 5.2 Electric Motors Shipments by Horsepower Rating for 2011

5.2.3 Pole-Configuration

Pole-configuration is another important equipment class setting criterion which DOE had 

to consider when selecting its representative units. For the preliminary analysis, DOE selected 4-

pole motors for all of its representative units. DOE chose not to vary the pole configuration of 

the various representative units it analyzed because it believed that doing so would provide the 

strongest relationship upon which to base its scaling. By keeping as many design characteristics 

constant as possible, DOE could more accurately identify how design changes affect efficiency 

across horsepower ratings. For example, if DOE compared the NEMA Premium efficiencies of a 

5-horsepower, 4-pole electric motor and 50-horsepower, 6-pole electric motor it would be 

difficult to determine how much of the difference was due to the change in horsepower rating 

and how much was due to the change of pole configuration. Additionally, DOE believes that the 

horsepower rating-versus-efficiency relationship is the most important (rather than pole 

configuration and enclosure-type versus efficiency) because there are significantly more 

horsepower ratings to consider. Finally, as illustrated in Figure 5.3, 4-pole electric motors 

constitute the largest fraction of the electric motors market. Electric motors built with 4-poles 

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

1 2 5 10 20 30 50 75 125 200 300 400 500

Percent of Shipments

Horsepower Rating
5

accounted for 69 percent of shipments in 2011, which was more than 2-pole, 6-pole, and 8-pole 

motor shipments combined.

Figure 5.3 Electric Motor Shipments by Pole Configuration for 2011

5.2.4 Enclosure Type

The final equipment class setting criterion that DOE had to consider when selecting its 

representative units was enclosure type. For the preliminary analysis, DOE elected to only 

analyze electric motors with totally enclosed, fan-cooled (TEFC) designs rather than open 

designs for all of its representative units. DOE selected TEFC motors because, as with pole 

configurations, DOE wanted as many design characteristics to remain constant as possible. 

Again, DOE believed that such an approach would allow it to more accurately identify the 

reasons for efficiency improvements. Finally, TEFC electric motors represented more than three 

times the shipment volume of open motors. Figure 5.4 shows the relative shipments of open and 

enclosed motors in the year 2011.

16.4%

70.0%

10.8%

2.9%

2-pole 4-pole 6-pole 8-pole
6

Figure 5.4 Electric Motor Shipments by Enclosure Type for 2011

As addressed above, when identifying which electric motors to evaluate, DOE considered 

equipment classes that represented motors with a significant volume of shipments. DOE also 

considered the necessity for scaling its engineering results. Therefore, DOE selected electric 

motors that would minimize any error that might be introduced through extrapolating between 

horsepower ratings, pole configurations, and enclosure types. As is discussed in section 5.7, 

DOE scaled the engineering analysis results of its analyzed representative units to all of the 

other, not-analyzed, equipment classes. Such scaling is necessary for the national impacts 

analysis (NIA). For more information on the NIA, please see preliminary TSD chapter 10. 

Table 5.2 presents the major design characteristics of the five representative units that DOE 

analyzed and will discuss in detail throughout this engineering analysis.
7

Table 5.2 Design Characteristics of the Five Representative Units Analyzed

Equipment Class 

Group Represented

Electric Motor

Design Type

Horsepower 

Rating

Pole 

Configuration Enclosure

1 and 3 NEMA Design B 5 4 Totally Enclosed, 

Fan Cooled

1 and 3 NEMA Design B 30 4 Totally Enclosed, 

Fan Cooled

1 and 3 NEMA Design B 75 4 Totally Enclosed, 

Fan Cooled

2 NEMA Design C 5 4 Totally Enclosed, 

Fan Cooled

2 NEMA Design C 50 4 Totally Enclosed, 

Fan Cooled

5.2.5 Equipment Class Group 1 (NEMA Design A and B Electric Motors)

DOE decided to focus the analysis of NEMA Design A and NEMA Design B electric 

motors on three representative units. When selecting these representative units, DOE used the 

data in Figure 5.2 and Figure 5.11 to select three representative units with high shipping volume 

that also evenly cover the entire range of horsepower ratings in the scope of this analysis. The 

graph in Figure 5.11 shows the average efficiencies of 4-pole, enclosed electric motors versus 

horsepower rating. This data was based on DOE’s electric motor database which was compiled 

from the most current electric motor manufacturer catalog data available. DOE analyzed this 

curve and segmented the graph into three primary sections.

5.2.6 Equipment Class Group 2 (NEMA Design C Electric Motors)

When selecting the representative units for equipment class group 2 (NEMA Design C 

electric motors), DOE referred again to Figure 5.2 which also represents the shipment volumes 

of NEMA Design C electric motors. Based on Figure 5.2, DOE selected a 5-horsepowerelectric 

motor again because of its high volume of shipments. To cover the higher horsepower ratings, 

DOE selected a 50-horsepower electric motor. DOE chose to base the analysis on the NEMA 

Design C equipment class group on two electric motors instead of three due to the lower 

production volumes of NEMA Design C electric motors and therefore somewhat limited 

equipment selection. DOE selected the 50-horsepowerrating because it falls between the 30-

horsepower and 75-horsepowerratings selected as representative units for equipment class group 

1.
8

5.2.7 Equipment Class Group 3 (Fire Pump Electric Motors)

According to National Fire Protection Association (NFPA) 20,Standard for the 

Installation of Stationary Pumps for Fire Protection, a motor that is used with a fire pump 

system must comply with NEMA MG1, comply with NEMA Design B standards, and be listed 

for fire pump service. So, with a few exceptions, fire pump electric motors are very similar to 

NEMA Design B electric motors. Namely, fire pump electric motors are not required to shut off 

if they are overheating, and they require more rigorous start/stop capabilities than general 

purpose NEMA Design B electric motors. Aside from these operating differences, fire pump 

electric motors are electromechanically similar to NEMA Design B electric motors. Therefore, 

DOE decided to base the analysis of fire pump electric motors on the engineering data produced 

from the representative units chosen for equipment class group1.

5.3 BASELINE AND CANDIDATE STANDARD LEVELS OF EFFICIENCY

For each representative unit selected, DOE identified a specific baseline electric motor as 

a fundamental design against which it would apply design changes to improve the electric 

motor’s efficiency. DOE chose the baseline electric motors to represent the typical 

characteristics of electric motors in the equipment class of the corresponding representative unit. 

The baseline efficiency level is used to determine energy savings and changes in price associated 

with moving to higher efficiency levels. Energy efficiency levels are termed “candidate standard 

levels” (CSLs) and are intended to help characterize the cost-efficiency relationship. Table 5.3

shows these efficiency levels for each of DOE’s selected representative units.

Table 5.3 Baseline Efficiency Ratings of Representative Units

Basic Characteristics of Electric Motors 

Analyzed

Baseline 

Efficiency %

Equipment Class 

Group

Design B, 5-horsepower, 4-pole, enclosed frame 82.5 1*

Design B, 30-horsepower, 4-pole, enclosed frame 89.5 1*

Design B, 75-horsepower, 4-pole, enclosed frame 93.0 1*

Design C, 5-horsepower, 4-pole, enclosed frame 87.5 2

Design C, 50-horsepower, 4-pole, enclosed frame 93.0 2

*Analysis of equipment class group 3 will be based on these representative units.

As discussed in chapters 2 and 3, DOE intends to expand the scope of energy 

conservation standards to include motors that were not previously covered by regulation. Those 

motor types not previously covered and that are now within the scope of coverage are listed in 

chapter 3 of the preliminary TSD. DOE used a motor database of efficiencies and up-to-date 

manufacturer motor catalogs to find motors with the lowest market efficiency. Since the 

expanded scope of energy conservation standards includes motors not previously subject to

efficiency standards, DOE selected motors whose baseline efficiencies were below the lowest 

energy conservation levels currently enforced for any motors (levels most recently prescribed by 

EISA 2007). DOE observed NEMA Design B vertical, hollow-shaft motors, currently outside the 

scope of regulation, with efficiency levels listed in Table 5.3. For the NEMA Design C 

equipment class group, DOE selected NEMA MG1-2011 Table 12-11 values as baseline 

efficiency levels. This approach is based on the lowest efficiency values DOE observed in motor 
9

catalogs for NEMA Design C motors. The NEMA Design C representative motors with the 

lowest observed efficiencies are also listed in Table 5.3. 

Should DOE not find any economic justification for amended energy conservation 

standards above the baseline efficiency level, subtype I and subtype II motors would remain 

subject to the same efficiency levels (i.e., different from each other) mandated by EISA 2007. 

Additionally, DOE notes that although the efficiencies in Table 5.3 represent the baseline, 

DOE’s efficiency distribution for equipment class group 1 shows a significant portion of motors 

already above the baseline efficiency level.

5.3.1 Candidate Standard Levels of Efficiency

NEMA MG1-2011 contains a table of standardized “nominal” full load efficiency values, 

Table 12-10, from which manufacturers may choose a value to label and market their electric 

motors. NEMA uses these standardized values of efficiency because of the variability in the 

performance of materials used in electric motors, such as electrical steel and copper, and the 

laboratory to laboratory test variation that can occur. Because of these possible sources of 

performance variation, NEMA and its members in industry use these standardized values of 

efficiencies, with associated guaranteed minimum values of efficiencies, to represent a specific 

electric motor model’s efficiency with a “band” of efficiency. The standardized values of NEMA 

nominal efficiencies found in Table 12-10 of NEMA MG1-2011 are fairly evenly spaced in 

terms of motor losses.a

As mentioned earlier, DOE selected a baseline model for each representative unit as a 

reference point against which to measure changes that may result from increasing an electric 

motor’s efficiency. Each increase in efficiency over the baseline level that DOE analyzed was 

assigned a CSL number. For the preliminary analysis, DOE based its baseline efficiency level, or 

CSL 0, on the lowest efficiency levels observed in motor catalog data for the motors DOE plans 

on including in the expanded scope of conservation standards. DOE selected five additional 

incremental CSLs for equipment class group 1 and three additional incremental CSLs for 

equipment class group 2 based on other industry specifications, market data, and software 

modeling.

 Each higher, incremental level of nominal efficiency represents a 

reduction in motor losses of roughly 10 percent. DOE followed a similar pattern when 

developing its higher CSLs (i.e., those above NEMA MG1-2011 Table 12-12 and Table 12-11).

Table 5.4 shows the CSLs for equipment class group1that DOE used for electric motors 

during the preliminary analysis. DOE based its first incremental CSL (CSL 1) on NEMA MG1-

2011, Table 12-11 and Table 20-Ab

 a Motor losses are calculated with the formula (1/η)-1, where η represents the value of efficiency. 

, which specify the nominal efficiency levels for motors that 

NEMA classifies as “energy efficient.” Table 12-11 is equivalent to the EPACT 1992 levels for 1 

to 200 horsepower NEMA Design B electric motors and the EISA 2007 levels for NEMA 

Design B electric motors with a horsepower rating greater than 200. EISA 2007 also mandated 

that general purpose electric motors (subtype I) from 1 to 200 horsepower meet efficiency levels 

b NEMA MG1-2011 Table 20-A includes efficiency levels for 6- and 8-pole motors at higher horsepower ratings 

(between 300 and 500 horsepower) that are omitted from Table 12-11. Table 20-A is a new addition to NEMA 

MG1-2011, and therefore the efficiency levels it specifies are not part of the most recent conservation standards set 

by EISA 2007. 
10

that correspond to NEMA MG1-2011, Table 12-12 (i.e., equivalent to NEMA Premium levels). 

However, equipment class group 1 includes motors that are considered general purpose electric 

motors (subtype II). For these electric motors, EISA 2007 mandated efficiency standards 

equivalent to Table 12-11, which is why DOE believes Table 12-11 is the appropriate CSL 1 to 

represent equipment class group 1.

Table 5.4 Candidate Standard Levels

CSL 

Number CSL Name

NEMA 

MG1-2011 

Table

Note

0 Baseline -- Lowest observed efficiency under expanded scope

1 Standard 12-11 & 20-A EPACT 1992 requirement, with additional efficiency 

levels added in NEMA MG1-2011

2 Premium 12-12 & 20-B

EISA 2007 requirement for general purpose electric 

motors (subtype I), with additional efficiency values 

added in NEMA MG1-2011

3 Best-in-Market -- One NEMA nominal efficiency level improvement 

relative to the Premium level

4 Incremental -- One NEMA nominal efficiency level improvement 

relative to the Best-in-Market

5 Maximum 

Technology -- One NEMA nominal efficiency level improvement 

relative to CSL 3

DOE based its second incremental CSL (CSL 2) on the NEMA Premium efficiency 

levels, found in NEMA MG1-2011 Tables 12-12 and 20-B. These tables typically represent a 

two or three NEMA band improvement above the previously mandated EPACT 1992 levels 

displayed in NEMA MG1-2011 Table 12-11. The third incremental CSL (CSL 3) is based on 

motors with the highest efficiencies observed in DOE’s motor database and up-to-date motor 

catalogs. Therefore CSL 3 motors have the “best-in-market” efficiencies for equipment class 

group 1 (ECG 1). This level was generally one NEMA band above the NEMA Premium level, or 

CSL 2. This level represents the best or near best efficiency level at which current manufacturers 

are producing electric motors. CSL 4 represents an incremental level between the maximum 

available efficiency and the maximum technology (“max-tech”) CSL. CSL 4 is based on a 

theoretical efficiency achievable using technologically feasible design options that were not 

screened out. CSL 5 represents the maximum technologically available or “max-tech” efficiency 

level. CSL 5 is based on a motor which incorporates a combination of the best materials 

potentially available for high-production motor manufacturing. This includes low-loss electrical 

steel and copper rotor motor technology. DOE based its value of efficiencies for CSL 4 and 5 on 

computer-modeled designs and subject matter expert (SME) feedback.

The CSLs for NEMA Design C motors (equipment class group 2) were selected

differently than for equipment class group 1. For equipment class group 2, DOE selected the 

NEMA MG1-2011 Table 12-11 values as the baseline efficiency level. This approach is based on 

the lowest efficiency values DOE observed in manufacturer catalogs for NEMA Design C 

motors, which apparently are the EPACT 1992 equivalent efficiency levels (as mandated by 

EISA 2007 under ‘general purpose electric motor (subtype II)’). Further CSLs for ECG 2 were 

selected based on computer modeling results, and are displayed in Table 5.5.
11

Table 5.5 shows the nominal efficiency values for each representative unit and each CSL. 

Cells with a ‘†’ indicate the efficiency number is a NEMA nominal nameplate efficiency rating 

of a physical electric motor which DOE purchased and tore down. Cells with a ‘*’ indicate the 

efficiency levels are from software modeling data gathered from DOE’s SME which were 

derived using various technology, material, and geometry changes. Cells with a ‘-’ indicate that 

DOE was not able to further increase efficiency levels for these representative units and still 

keep an electric motor design within the proper specifications.

Table 5.5 Candidate Standard Levels for each Representative Unit

Candidate 

Standard 

Level

5-Horsepower 

Design B 

Efficiency (%)

30-Horsepower 

Design B 

Efficiency (%)

75-Horsepower 

Design B 

Efficiency (%)

5-Horsepower 

Design C 

Efficiency (%)

50-Horsepower 

Design C 

Efficiency (%)

0 82.5† 89.5† 93.0† 87.5† 93.0†

1 87.5† 92.4† 94.1† 89.5* 94.1*

2 89.5† 93.6* 95.4† 90.2* 94.5*

3 90.2† 94.1† 95.8† 91.0* 95.0*

4 91.0* 94.5* 96.2* - -

5 91.7* - 96.5* - -

†Indicates the efficiency of a purchased and physically torn-down electric motor

*Indicates the efficiency of a software-modeled electric motor

5.4 ENGINEERING ANALYSIS METHODOLOGY

As stated, the engineering analysis estimates the cost increment for the efficiency 

improvement potential of individual design options or combinations of design options that pass 

the four criteria in the screening analysis. DOE uses this cost-efficiency relationship, developed 

in the engineering analysis, in the LCC analysis.

DOE can use three methodologies to generate the manufacturing costs needed for the 

engineering analysis. These methods are:

1. the design-option approach – reporting the incremental costs of adding design options to 

a baseline model;

2. the efficiency-level approach – reporting relative costs of achieving improvements in 

energy efficiency; and

3. the reverse engineering or cost assessment approach – involving a "bottom up" 

manufacturing cost assessment based on a detailed bill of materials derived from electric 

motor teardowns.

Because DOE targeted certain nominal efficiency levels when improving baseline 

efficiencies and relied on tear-downs of electric motors, DOE’s analysis for the electric motor 

rulemaking is a combination of the efficiency-level approach and the reverse engineering 

approach. DOE created baseline costs from bills of materials of electric motor tear-downs and 
12

then determined the costs of increasing efficiency levels based on material or technology 

changes.

5.4.1 Subcontractor Tear-downs

Due to limited manufacturer feedback concerning cost data and production costs, DOE 

derived its production and material costs by having a professional motor laboratoryc disassemble 

and inventory the physical electric motors purchased. DOE performed tear-downs on the electric 

motors representing CSL 0 through 3 for equipment class group 1as well as electric motors 

representing CSL 0 for equipment class group 2. These tear-downs provided DOE the necessary 

data to construct a bill of materials, which DOE could normalize using a standard cost model and 

markup to produce a projected manufacturer selling price. DOE used the MSP derived from the 

engineering tear-down paired with the corresponding nameplate nominal efficiency to report the 

relative costs of achieving improvements in energy efficiency. DOE derived material prices from 

a consensus of current, publicly available data, manufacturer feedback, and conversations with 

its subject matter experts. DOE supplemented the findings from its tests and tear-downs through: 

(1) a review of data collected from manufacturers about prices, efficiencies, and other features of 

various models of electric motors, and (2) interviews with manufacturers about the techniques 

and associated costs used to improve efficiency. 

DOE’s engineering analysis documents the design changes and associated costs when 

improving electric motor efficiency from the baseline level up to a max-tech level. This includes 

considering improved electrical steel for the stator and rotor, interchanging aluminum and copper 

rotor bar material, increasing stack length, and any other applicable design options remaining 

after the screening analysis. As each of these design options are added, the manufacturer’s cost 

generally increases and the electric motor’s efficiency improves. 

5.4.2 Subcontractor Software Designs

DOE worked with technical experts to develop the highest efficiency levels (i.e., the 

max-tech levels) technologically feasible for each representative unit analyzed. DOE used a 

combination of electric motor software design programs and SME input. DOE retained an 

electric motor expertd

 c The Center for Electromechanics University of Texas at Austin, a 140,000 sq. ft. lab with 40 years of operating 

experience with teardowns overseen by Dr. Angelo Gattozzi, an electric motor expert with previous industry 

experience.

with design experience and software, who prepared a set of designs with 

increasing efficiency. Additionally, DOE purchased another software modeling suite for the 

SME to check against his personal modeling software. The SME also checked his designs 

against tear-down data and made alterations to some of his designs to create the most practical 

designs possible. As new designs were created, careful attention was paid to the critical 

performance characteristics defined in NEMA MG-1 2009 Tables 12-2, 12-3, 12-4, and 

paragraph 12.35.1, which define locked rotor torque, breakdown torque, pull-up torque and 

maximum locked rotor currents, respectively. For a given representative unit, DOE ensured that 

the modeled electric motors met the same set of constraints (i.e., performance standards) as the 

purchased electric motors. This was done to ensure that the utility of the baseline unit was 

conserved as efficiency was improved through the application of various design options. 

d Dr. Howard Jordan, Ph.D, an electric motor design expert with over 40 years of industry experience.
13

Additionally, DOE limited its modeled stack length increases based on tear-down data and the 

maximum “C” dimensions found in manufacturer’s catalogs.e

DOE limited the amount by which it would increase the stack length of its softwaremodeled electric motors to preserve the utility of the baseline model torn down. The maximum 

stack lengths used in the software-modeled CSLs were determined by first analyzing the stack 

lengths and C dimensions of torn-down electric motors. Then, DOE analyzed the C dimensions 

of various electric motors in the marketplace conforming to the same design constraints as the 

representative units (same NEMA design type, horsepower rating, NEMA frame number, 

enclosure type, and pole configuration). For each representative unit, DOE found the largest C 

dimension currently available on the marketplace and estimated a maximum stack length based 

on the stack length to C dimension ratios of motors it tore down. The resulting product was the 

value that DOE chose to use as the maximum stack length in its software modeled designs. Table 

5.6 shows the stack lengths of torn down CSLs and stack lengths used in the software modeled 

CSLs. The efficiency levels of the software modeled CSLs are displayed in Table 5.5.

.

 e The C dimension of an electric motor is the length of the electric motor from the end of the shaft to the end of the 

opposite side’s fan cover guard. Essentially, the C dimension is the overall length of an electric motor for proper 

mounting and interface with the driven equipment.
14

Table 5.6 Stack Length and C Dimension Measurements of Torn Down and Modeled

Motors

Representative Unit CSL Stack Length

(in)

5 HP, Design B

0 2.8*

1 3.47

2 5.14

3 4.65

4 5.32**

5 5.32**

30 HP, Design B

0 7.88*

1 5.53

2 6.00**

3 6.74

4 7.00**

75 HP, Design B

0 8.15*

1 10.23

2 10.58

3 11.33

4 12.0**

5 13.0**

5 HP, Design C

0 4.75

1 4.25**

2 5.32**

3 5.32**

50 HP, Design C

0 8.67

1 9.55**

2 9.55**

3 9.55**

*Represents stack length of a vertical, hollow-shaft motor.

**Represents stack length of a software modeled motor.

5.5 COST MODEL

DOE uses a standard method of cost accounting to determine the costs associated with 

manufacturing. This methodology is illustrated in Figure 5.5, where production costs and nonproduction costs are combined to determine the full cost of a product.
15

Figure 5.5 Standard Method of Cost Accounting for Standards Rulemaking

DOE developed estimates of some of the cost multipliers shown in Figure 5.5 by 

reviewing Security and Exchange Commission (SEC) SEC-10K reports from electric motor 

manufacturers, and examining previous, relevant, rulemakings, and through conversations with 

industry experts. Together, the full production cost and the non-production costs equal the full 

cost of the product. Full production cost is a combination of direct labor, direct materials, and 

overhead. The overhead contributing to full production cost includes indirect labor, indirect 

material, maintenance, depreciation, taxes, and insurance related to company assets. Nonproduction costs include the cost of selling (market research, advertising, sales representatives, 

logistics), general and administrative costs, research and development, interest payments and 

profit factor (not shown in the figure).

After the designs examined by DOE’s motor experts were completed or the electric 

motors were torn down and the parts were inventoried, the next step was applying a consistent 

cost model to all of them. A standard bill of materials (BOM) was constructed that includes 

direct material costs. From this BOM, labor time estimates (along with associated costs) were 

added and various manufacturer markups were applied to create an MSP. DOE presents a 

summary of the production costs and non-production costs for each of the representative units 

analyzed in Appendix 5A.

Direct

Labor

Direct

Labor Direct

Material

Direct

Material Overhead Overhead Selling Selling General &

Admin.

General &

Admin. R & D R & D Interest Interest

Indirect Labor

Full Production Cost 1 Non-Production Cost

Indirect Material

Maintenance

Depreciation

Taxes

Insurance related

to assets

Mkt. research

Advertising

POS promotion

Sales person

salary + travel

+ commission

Logistics

- Warehousing

- Delivery

- Record

 keeping

- Order entry/

 processing

Costs of

service &

staff units

General

corporate

costs

- comp. etc.

Costs

associated

with efforts

to find new

or improved

products or

production

processes

Costs

of

borrowing

funds

1 Tax Reform Act of 1986, essentially, requires companies to measure cost of goods sold as the full production cost of the goods sold.

Full Cost of Product Full Cost of Product

Code

compliance

Modernization

Cust. service
16

5.5.1 Constructing a Bill of Materials

The BOM calculated for each design contained three types of material costs: variable, 

insulation, and hardware. The variable costs considered are those portions of the BOM that vary 

based on the cost of the material and the amount of that material used in the design. For example, 

stator and rotor lamination costs are variable costs because the material price for the different 

steel grades changes as does the volume of steel needed for each design. The insulation cost was 

aggregated due to the difficulty in pricing out all components of the insulation system. Based on 

SME feedback, DOE assumed increased efficiency does not incur notable increases in insulation 

system costs. Therefore, insulation costs increase as representative unit horsepower increases, 

but remain constant across all CSLs for each representative unit. The total price for insulation 

was also derived from SME input. Finally, hardware costs are an aggregate cost for all electric 

motor hardware components. This includes nuts, bolts, gaskets, washers and other miscellaneous 

hardware components. As with the insulation costs, the hardware cost was aggregated due to the 

difficulty of pricing individual components. DOE believes hardware costs account for a small 

percentage of the total material costs of an electric motor and therefore does not believe this 

aggregation method will have a detrimental impact on the accuracy of the MSP. Additionally, 

because the motors (within a representative unit) all come from the same manufacturer, DOE 

believes these costs are likely to be very similar and have minimal variation. The aggregate 

hardware cost, which is unique for each horsepower rating, was also derived based on SME input 

and information received about the teardowns.

Each item in the BOM is organized by the type of cost (i.e., variable, insulation, and 

hardware) and the component of the electric motor to which they apply. The variable costs 

portion of the BOM includes the following subheadings, each with an itemized parts list: stator 

assembly, rotor assembly, and other major costs. The insulation cost section of the BOM 

includes subheadings for each individual component identified during teardown, however they 

are not priced out individually. As discussed above, an aggregate price is used to cover this entire 

section. This aggregate price is unique for different horsepower ratings. The hardware cost 

section of the BOM includes subheadings for individual hardware items identified during the 

teardown, but again like the insulation costs, they are not individually priced. There is one 

aggregate price used that covers all of the hardware components. This aggregate price is unique 

for each horsepower rating.

The subheadings that have an itemized list of components include the stator assembly, 

rotor assembly, and other major costs. The stator assembly’s itemized lists include prices for 

steel laminations and copper wire. The rotor assembly portion of the BOM includes prices for 

laminations, rotor conductor material, (either aluminum or copper) and shaft extension material. 

The other major costs heading contains items for the frame material and base, terminal housing 

components, bearing-type, and end-shield material.

DOE presents a detailed BOM for one design from each of the electric motor categories 

analyzed in Appendix 5B. The discussion below describes the level of detail contained in the bill 

of materials presented in the appendix.
17

5.5.2 Labor Costs and Assumptions

Due to the varying degree of automation used in manufacturing electric motors, labor 

costs differ for each representative unit. DOE analyzed teardown results to determine which 

electric motors were machine wound and which electric motors were hand wound and based on 

this analysis, DOE applied a higher labor hour amount for the hand-wound electric motors. For 

the max-tech software modeled electric motors, DOE always assumed hand-winding and 

therefore a higher labor hour amount. Labor hours for each of the representative units were based 

on SME input and manufacturer interviews. 

DOE used the same hourly labor rate for all electric motors analyzed. The base hourly rate 

was developed from the 2007 Economic Census of Industry,f

Table 5.7

published by the U.S. Census 

Bureau, as well as manufacturer and SME input. The base hourly rate is an aggregate rate of a 

foreign labor rate and a domestic labor rate. DOE weighed the foreign labor rate more than the 

domestic labor rate due to manufacturer feedback indicating off-shore production accounts for a 

majority of electric motor production by American-based companies. Several markups were 

applied to this hourly rate to obtain a fully burdened rate which was intended to be representative 

of the labor costs associated with manufacturing electric motors. shows the markups 

that were applied, their corresponding markup percentage, and the new burdened labor rate. 

Table 5.7 Labor Markups for Electric Motor Manufacturers

Item description Markup percentage Rate per hour

Labor cost per hour $ 10.87

Indirect Production 33 % $ 14.46

Overhead 30 % $ 18.79

Fringe† 24 % $ 23.40

Assembly Labor Up-time†† 43 % $ 33.46

Cost of Labor Input to Spreadsheet $ 33.46

 Cost per hour is an aggregate number drawn from U.S. Census Bureau, 2007 Economic Census of Industry, 

published December 2010 and foreign labor rate estimates based on manufacturer feedback.

 Indirect Production Labor (Production managers, quality control, etc.) as a percent of direct labor on a cost basis. 

Navigant Consulting, Inc. (NCI) estimate.

 Overhead includes commissions, dismissal pay, bonuses vacation, sick leave, and social security contributions. 

NCI estimate.

† Fringe includes pension contributions, group insurance premiums, workers compensation. Source: U.S. Census 

Bureau, 2007 Economic Census of Industry, published December 2010. Data for NAICS code 335312 “Electric 

Motor and Generator Manufacturer” total fringe benefits as a percent of total compensation for all employees (not 

just production workers).

†† Assembly labor up-time is a factor applied to account for the time that workers are not assembling product 

and/or reworking unsatisfactory units. The markup of 43 percent represents a 70 percent utilization (multiplying by 

100/70). NCI estimate.

5.5.3 Manufacturer Markups

DOE used the three markups described below to account for non-production costs that 

are part of each electric motor leaving a manufacturer’s facility. Handling and scrap factor, 

 f U.S. Census Bureau, 2007 Economic Census of Industry
18

overhead, and non-production markups will vary from manufacturer to manufacturer because 

their profit margins, overheads, prices paid for goods, and business structures vary. DOE 

prepared estimates for these three non-production cost manufacturer markups from Securities 

and Exchange Commission (SEC) Form 10K annual reports, and conversations with 

manufacturers and experts.

• Handling and scrap factor: 2.5 percent markup. This markup was applied to the direct 

material production costs of each electric motor. It accounts for the handling of material 

(loading into assembly or winding equipment) and the scrap material that cannot be used 

in the production of a finished electric motor (e.g., lengths of wire too short to wind).

• Factory overhead: 17.5 percent markup. Factory overhead includes all the indirect costs 

associated with production, indirect materials and energy use, taxes, and insurance. DOE 

only applies factory overhead to the direct material production costs (including the 

handling and scrap factor). The overhead increases to 18.0 percent when copper die 

casting is used in the rotor. This accounts for additional energy, insurance, and other 

indirect costs associated with the copper die-casting process.

• Non-production: 37 – 45 percent markup. This markup reflects costs including sales and 

general administrative, research and development, interest payments, and profit factor. 

DOE applies the non-production markup to the sum of the direct material production, the 

direct labor, and the factory overhead. For the analyzed electric motors at or below 30-

horsepower this markup was 37 percent and for electric motors above 30-horsepower this 

markup was 45 percent. This increase accounts for the extra profit margin manufacturers 

may receive on larger electric motors that are sold in smaller volumes.

5.6 RESULTS OF ENGINEERING ANALYSIS

DOE used the five representative units to develop five manufacturer selling price versus

nominal full-load efficiency curves, three for equipment class group 1 (also used for equipment 

class group 3), and two for equipment class group 2. Figure 5.6 through Figure 5.10 provide the 

manufacturer selling price versus efficiency curves and Table 5.8 through Table 5.21present the 

tabulated results.

5.6.1 NEMA Design B, 5-Horsepower, 4-Pole, Enclosed Electric Motor

Figure 5.6 presents the relationship between MSP and nominal full-load efficiency for the 

5-horsepower, Design B, 4-pole, enclosed electric motor that was analyzed. Using the tear-down 

results for CSLs 0 to 3, DOE determined that the manufacturer of these electric motors increased 

the stack length and used various combinations of increasing the stator copper, electrical steel, 

or rotor conductor, as well as design changes, to improve the electric motor’s efficiency.

DOE used software modeling to develop CSLs 4 and 5. DOE increased the efficiency 

level of these representative units and all other representative units by employing a combination 

of changing the slot fill, increasing stator copper or electrical steel amounts, changing the type or 

amount of rotor conductor material, and changing specifications of the motor design such as 
19

rotor cage geometry or rotor skew. For CSL 5, which is the max-tech efficiency level, DOE used 

a die-cast copper rotor conductor design while keeping the stack length the same as the motor 

design used for CSL 4. For CSL 5, DOE assumed a 10 percent labor hour increase above CSL 4. 

Material cost increases, such as low loss electrical steel and increased stator copper, 

account for the relatively large increase in MSP from CSL 3 to CSL 4. Additionally, DOE 

assumed a hand-wound labor hour assumption for CSL 4 and 5 which adds to the relatively large 

jump in MSP when moving to CSL 4. All of the motors torn down and used for CSLs 0 through 

3 were observed to have machine-wound stators.

Figure 5.6 NEMA Design B, 5-Horsepower, 4-Pole, Enclosed Electric Motor 

Engineering Analysis Curve

Table 5.8presents the same engineering analysis results in tabular form, including the 

nominal full-load efficiency values and the MSPs. From CSL 0 through CSL 3, MSP increases 

by amounts varying up to 10 percent. When moving from CSL 3 to 4 and from CSL 4 to 5, MSP 

increases by $153 or about 41 percent and $56 or 11 percent, respectively, for consecutive loss 

reductions of roughly10 percent. Again, the large price increases when moving to CSLs 4 and 5 

are a result of the use of increased labor hour and material increases. Additionally, CSL 5 

employs a die-cast copper conductor in the rotor, which accounts for some of the MSP increase 

of CSL 5. At the time of publishing, copper was approximately 2.7 times more expensive than 

aluminum per pound and is three times denser. Therefore, filling an equal volume space with 

cast copper is almost nine times more expensive than filling the same volume with cast 

aluminum.
20

Table 5.8 Efficiency and Manufacturer Selling Price Data for the NEMA Design B,

5-Horsepower Motor

CSL Nominal Full-Load Efficiency (%) MSP ($)

0 82.5 324

1 87.5 326

2 89.5 358

3 90.2 370

4 91.0 523

5 91.7 579

Table 5.9 presents some of the design and performance specifications associated with the 

six 5-horsepower NEMA Design B electric motors presented above including stator copper 

weight, rotor conductor weight, and electrical steel weight. Table 5.10 shows the NEMA MG1-

2011 Design B performance criteria as well as those design parameters for the two softwaremodeled electric motors.

Table 5.9 NEMA Design B, 5-Horsepower, 4-Pole, Enclosed Motor Characteristics

Parameter Units CSL 0 CSL 1 CSL 2 CSL 3 CSL 4* CSL 5*

Efficiency % 82.5 87.5 89.5 90.2 91.0 91.7

Line Voltage V 460 460 460 460 460 460

Full Load Speed RPM 1,745 1,745 1,760 1,755 1,773 1,776

Full Load Torque Nm 20.3 20.4 20.3 20.4 20.1 20.1

Current A 6.9 6.5 6.3 6.2 6.3 6.0

Steel - M56 M47 M47 M47 M36 M36

Rotor Conductor 

Material - Aluminum Aluminum Aluminum Aluminum Aluminum Copper

Approximate 

Slot Fill % 43.5% 57.2% 70.0% 68.6% 82.4% 85.2%

Stator Wire 

Gauge AWG 19 19 19 20 20 20

Stator Copper 

Weight lbs 8.4 10.1 10.1 12.2 14.4 14.4

Rotor Conductor 

Weight lbs 2.63 2.87 2.6 3.42 2.7 9.1

Stack Length In 2.8 3.47 5.14 4.65 5.32 5.32

Housing Weight lbs 8 9 22 12 14 14

* Software modeled motor
21

Table 5.10 NEMA Design B, 5-Horsepower, 4-Pole, Enclosed Motor Modeled 

Characteristics

Parameter Units Design B Limit CSL 4 CSL 5

Efficiency % - 91.0 91.7

Breakdown Torque % of full-load 225 (minimum) 323 305

Pull-Up Torque % of full-load 130 (minimum) 245 214

Locked-Rotor Torque % of full-load 185 (minimum) 245 214

Locked-Rotor Current A 46 (maximum) 41.6 43.9

5.6.2 NEMA Design B, 30-Horsepower, 4-Pole, Enclosed Electric Motor

Figure 5.7 presents the relationship between the MSP and nominal full-load efficiency for 

the 30-horsepower, Design B, 4-pole, enclosed polyphase motor analyzed. Using tear-down 

results for CSLs 0, 1, and 3, DOE determined that the manufacturer of these motors used a 

combination of material grade, material quantities, and design changes to increase the electric 

motor’s efficiency.

Although motors are available at the CSL 2 efficiency level (93.6 percent), DOE used 

software modeling to simulate this motor because the CSL 2 motor DOE purchased for teardown had a nameplate and catalog efficiency rating that did not match the efficiency found on 

the manufacturer’s website. Additionally, tear-down results of the CSL 2 motor revealed it to 

have more stack length, electrical steel, and rotor aluminum as well as lower-loss electrical steel 

than the CSL 3 motor, which has a nameplate efficiency of 94.1 percent. CSL 2 also had 8 

percent lower losses than CSL 3 based on IEEE 112B test results. Results of the IEEE 112B test, 

as well as tear-down results, are illustrated in Table 5.11.

Table 5.11 30-Horsepower CSL 2 and CSL 3 Testing and Tear-down Results

Parameter CSL 2 CSL 3 Percent change 

over CSL 3

Nameplate and Catalog efficiency (%) 93.6 94.1 -

Website efficiency (%) 94.1 94.1 -

Tested efficiency (%) 94.29 93.88 8†

Stack length (in) 8.21 6.74 22

Electrical steel grade* M36 M47 -

Weight of electrical steel (lbs) 201 156 29

Weight of stator copper (lbs) 37 47 -21

Weight of rotor-slot aluminum (lbs) 6.6 5.9 12

* Estimate based on DOE’s metallurgical analysis

† Based on losses

DOE decided that its purchased CSL 2 motor had incorrect nameplate efficiency. This 

decision is based on comparing the test and tear-down results to the CSL 3 motor. Therefore, 

DOE decided to use software modeling to replace the CSL 2 motor tear-down, for the 

preliminary analysis. The CSL 2 software modeled motor is based on measurements taken from 

the CSL 1 and CSL 3 tear-down results, such as stack length, material weights, and electrical 

steel grades. The resulting CSL 2 motor specifications are listed in Table 5.13.
22

DOE also used software modeling to develop CSL4. For this design DOE used a copper 

rotor and low-loss electrical steel to achieve efficiencies higher than the purchased electric 

motors. Using a die-cast copper conductor in the rotor also reduced the stack length of CSL 4 

compared to the other 30 horsepower CSLs analyzed. Shortening the stack length helps lower the 

cost of this max-tech design. CSL 4’s primary cost increases arise from an increased labor hour 

amount based on a hand-wound labor assumption as well as other material quantity increases.

Unlike the 5-horsepower and 75-horsepower Design B representative units, the 30-

horsepower Design B representative unit does not have a CSL 5. DOE attempted to improve the 

design of CSL 4 in an effort to reach the next highest NEMA nominal efficiency level. However, 

DOE was unable to reduce losses by at least 10 percent (one NEMA nominal efficiency band), 

and therefore DOE was not able to achieve the next NEMA nominal efficiency level.

Figure 5.7 NEMA Design B, 30-Horsepower, 4-Pole, Enclosed Electric Motor 

Engineering Analysis Curve

Table 5.12 presents the engineering analysis results in a tabular form, including the fullload efficiency values and the MSPs. From CSL 0 to 3, DOE found that the full-load efficiency 

would increase 5.6 nominal percentage points over the baseline, CSL 0, which represents about a 

47 percent reduction in electric motor losses. The increase in MSP to move from CSL 0 to CSL 3 

is $377, or about a 46 percent increase in MSP over CSL 0. Moving from CSL 0 to CSL 4 

provides a 50 percent reduction in electric motor losses for a MSP increase of $1,109 or about a 

135 percent MSP increase over CSL 0.
23

Table 5.12 Efficiency and Manufacturer Selling Price Data for the NEMA Design B, 30-

Horsepower Motor

CSL Nominal Full-Load Efficiency (%) MSP ($)

0 89.5 827

1 92.4 1,044

2 93.6 1,193

3 94.1 1,204

4 94.5 1,936

Table 5.13 presents some of the design and performance specifications associated with 

the five 30-horsepower designs presented above, including stator copper weight, rotor conductor 

weight, and electrical steel weight. Table 5.14 shows the NEMA MG1-2009 Design B 

performance criteria as well as those design parameters for the software modeled electric motor.

Table 5.13 NEMA Design B, 30-Horsepower, 4-Pole, Enclosed Motor Characteristics

Parameter Units CSL 0 CSL 1 CSL 2* CSL 3 CSL 4*

Efficiency % 89.5 92.4 93.6 94.1 94.5

Line Voltage V 230 460 460 460 460

Full Load Speed RPM 1,755 1,765 1,768 1,770 1,784

Full Load Torque Nm 121.6 121.4 120.8 120.6 119.6

Current A 37 37 36 36 37

Steel - M56 M56/M47 M47 M47 M36

Rotor Conductor Material - Aluminum Aluminum Aluminum Aluminum Copper

Approximate Slot Fill % 48.4 84.0 70.0 70.0 83.2

Stator Wire Gauge AWG 18 17 16 18 18

Stator Copper Weight lbs 20.2 43.5 45.2 47.7 74.5

Rotor Conductor Weight lbs 8.25 9.5 7.5 13.66 42.6

Stack Length In 7.88 5.53 6.00 6.74 7.00

Housing Weight lbs 21 130 131 147 152

* Software modeled motor

Table 5.14 NEMA Design B, 30-Horsepower, 4-Pole, Enclosed Motor Modeled 

Characteristics

Parameter Units Design B Limit CSL 2 CSL 4

Efficiency % - 93.6 94.5

Breakdown Torque % of full-load 200 (min.) 265.6 202

Pull-up Torque % of full-load 105 (min.) 173.3 139

Locked Rotor Torque % of full-load 150 (min.) 183.2 154

Locked Rotor Amps A 217.5(max.) 204 208

5.6.3 NEMA Design B, 75-Horsepower, 4-Pole, Enclosed Electric Motor

Figure 5.8 presents the relationship between the MSP and nominal full-load efficiency for 

the 75-horsepower, Design B, 4-pole enclosed electric motor analyzed. Using tear-down results 

for CSLs 0 through 3, DOE determined that the manufacturer of these electric motors increased 
24

the stack length and other material amounts to increase the electric motor’s efficiency levels 

from 93.0 percent to 95.8 percent. The torn-down electric motor representing CSL 3 used 

increased rotor aluminum and stator copper as well as an increased stack length to achieve 95.8 

percent efficiency.

DOE used software modeling to develop CSL 4. For this design, DOE used a die-cast 

copper conductor in the rotor and low-loss electrical steel in the rotor and stator to achieve 

efficiencies higher than commercially available electric motors. The stack length of the electric 

motor for CSL 4 is higher than the stack length of lower CSLs for the 75-horsepower Design B 

electric motors analyzed, but shorter than the electric motor for CSL 5. 

To develop the max-tech efficiency level, CSL 5, DOE again used software modeling. 

DOE continued to use a die-cast copper rotor conductor design, but increased the stack length to 

an estimated maximum stack length. This maximum stack length was calculated based on the 

method described previously in section 5.4.2. The assumption of manual-labor hour amounts and 

the use of die-cast copper conductors in CSL 4 and 5’s rotors account for the larger-than-typical 

price increase between CSL 3 and CSL 4 for the 75-horsepower Design B representative units.

Figure 5.8 NEMA Design B, 75-Horsepower, 4-Pole, Enclosed Motor Engineering 

Analysis Curve

Table 5.15 presents the same engineering analysis results in a tabular form, including the 

nominal full-load efficiency values and the MSPs. Moving from CSL 0 to CSL 3, DOE found 

that the full-load efficiency would increase 2.4 nominal percentage points over the baseline, CSL 

0, which represents about a 42 percent reduction in electric motor losses. The increase in MSP to 

move from CSL 0 to CSL 3 is about $748 or about a 41 percent increase in MSP over CSL 0. 

Moving from CSL 0 to CSL 4 provides a 47 percent reduction in electric motor losses for a MSP 

increase of $1,520, which constitutes an 83 percent MSP increase over the CSL 0 electric motor. 
25

To increase the efficiency from CSL 0 to the max-tech efficiency of CSL 5 there is a 52 percent 

reduction in motor losses for about a 102 percent increase in MSP of $1,879.

Table 5.15 Efficiency and Manufacturer Selling Price Data for the NEMA Design B, 75-

Horsepower Motor

CSL Nominal Full-Load Efficiency 

(%) MSP ($)

0 93.0 1,833

1 94.1 1,994

2 95.4 2,270

3 95.8 2,581

4 96.2 3,353

5 96.5 3,712

Table 5.16 presents some of the design and performance specifications associated with 

the six 75-horsepower designs presented above, including stator copper weight, rotor conductor 

weight, and electrical steel weight. Table 5.17 shows the NEMA MG1-2011 Design B 

performance criteria as well as those design parameters for the two software modeled electric 

motors.

Table 5.16 NEMA Design B, 75-Horsepower, 4-Pole, Enclosed Motor Characteristics

Parameter Units CSL 0 CSL 1 CSL 2 CSL 3 CSL 4* CSL 5*

Efficiency % 93.0 94.1 95.4 95.8 96.2 96.5

Line Voltage V 460 460 460 460 460 460

Full Load Speed RPM 1,775 1,785 1,781 1,785 1,788 1,789

Full Load Torque Nm 299.8 299.8 302.3 300.8 299.6 299.6

Current A 88 91.8 89.4 88.6 89.8 91.9

Steel - M56 M47 M47 M47 M36 M36

Rotor Conductor 

Material - Aluminum Aluminum Aluminum Aluminum Copper Copper

Approximate Slot 

Fill % 48.0 44.5 70.0 70.0 85.1 83.4

Stator Wire Gauge AWG 17 12 12 15 14 14

Stator Copper 

Weight lbs 77.8 71 82 136 127 160

Rotor Conductor 

Weight lbs 31.0 20.7 27.3 38.5 79 84.3

Stack Length In 8.15 10.23 10.58 11.37 12.00 13.00

Housing Weight lbs 130 79 168 180 190 206

* Software modeled motor
26

Table 5.17 NEMA Design B, 75-Horsepower, 4-Pole, Enclosed Motor Modeled 

Characteristics

Parameter Units Design B Limit CSL 4 CSL 5

Efficiency % - 96.2 96.5

Breakdown Torque % of full-load 200 (min.) 218.2 202.0

Pull-up Torque % of full-load 100 (min.) 135 139.3

Locked Rotor Torque % of full-load 140 (min.) 163.8 163.7

Locked Rotor Amps A 542.5(max.) 530.7 541.3

5.6.4 NEMA Design C, 5-Horsepower, 4-Pole, Enclosed Electric Motor

Figure 5.9 presents the relationship between the MSP and nominal full-load efficiency for 

the 5-horsepower, NEMA Design C, 4-pole, enclosed electric motor analyzed. DOE purchased 

only one NEMA Design C electric motor for its tear-down analysis. The remaining three CSLs 

were based on software modeled electric motors. Therefore, discussion of the NEMA Design C 

revolves around the design changes DOE’s software modeling expert chose to implement to 

increase the efficiency levels of the electric motors. 

DOE achieved the CSL 1 efficiency level by using a lower loss grade of electrical steel 

and increasing the slot fill higher than that of the CSL 0 electric motor. The CSL 1 electric motor 

also boasts a smaller stack length and a lower slot fill percentage than the CSL 0 electric motor. 

DOE increased the efficiency of the CSL 2 motor design by keeping an aluminum die-cast rotor 

conductor cage, but increasing the stack length to the maximum stack length calculated via the 

methodology described in section 5.4.2. This increased the amount of electrical steel and stator 

copper material by 25 and 52 percent, respectively. DOE achieved the CSL 3 efficiency by 

employing a copper die-cast rotor conductor and while maintaining the same stack length as the 

CSL 2 motor. The die-cast copper rotor conductor allowed the CSL 3 design to reduce its stator 

copper winding by almost 15 percent while still achieving a higher efficiency than CSL 2. 
27

Figure 5.9 NEMA Design C, 5-Horsepower, 4-Pole, Enclosed Motor Engineering 

Analysis Curve

Table 5.18 presents the same engineering analysis results in a tabular form, including the 

nominal full-load efficiency values and the MSPs. Moving from CSL 0 to CSL 2, DOE found 

that the nominal full-load efficiency would increase 2.7 percentage points over the baseline, CSL 

0, which represents a 24 percent reduction in electric motor losses. The increase in MSP to move 

from CSL 0 to CSL 2 is $198, or about a 61 percent increase in MSP over CSL 0. Increasing 

from CSL 2 to CSL 3 would result in a 10 percent reduction in losses and a 7 percent increase in 

MSP. 

Table 5.18 Efficiency and Manufacturer Selling Price Data for the NEMA Design C, 5-

Horsepower Motor

CSL Nominal Full-Load Efficiency (%) MSP ($)

0 87.5 324

1 89.5 348

2 90.2 522

3 91.0 559

Table 5.19 presents some of the design and performance specifications associated with 

the four Design C, 5-horsepower electric motors presented above. The table includes stator 

copper weight, rotor conductor weight, and electrical steel weight. Table 5.20 shows the NEMA 

MG1-2009 Design C performance criteria as well as those design parameters for the three 

software modeled electric motors.
28

Table 5.19 NEMA Design C, 5-Horsepower, 4-Pole, Enclosed Motor Characteristics

Parameter Units CSL 0 CSL 1 CSL 2 CSL 3

Efficiency % 87.5 89.5 90.2 91.0

Line Voltage V 460 460 460 460

Full Load Speed RPM 1,750 1,762 1,767 1,776

Full Load Torque lb-ft 15 14.9 14.9 14.8

Current A 7.1 8.4 7.1 6.5

Steel - M47 M36 M36 M36

Rotor Conductor Material - Aluminum Aluminum Aluminum Copper

Approximate Slot Fill % 67.9 79.9 83.9 82.9

Stator Wire Gauge AWG 18 18 18 18

Stator Copper Weight lbs 10 9.9 15 12.8

Rotor Conductor Weight lbs 2.2 2.0 2.4 7.8

Stack Length in 4.75 4.25 5.32 5.32

Frame Weight lbs 12 11 14 14

Table 5.20 NEMA Design C, 5-Horsepower, 4-Pole, Enclosed Motor Modeled 

Characteristics

Parameter Units Design C Limit CSL 1 CSL 2 CSL 3

Efficiency % - 89.5 90.2 91.0

Breakdown Torque % of full-load 200 (min.) 293 260.2 260.8

Pull-up Torque % of full-load 180 (min.) 283.9 243.6 260.8

Locked Rotor Torque % of full-load 255 (min.) 344.1 297.9 260.8

Locked Rotor Amps A 46 (max.) 38.5 38.3 41.7

5.6.5 NEMA Design C, 50-Horsepower, 4-Pole, Enclosed Electric Motor

Figure 5.10 presents the relationship between the MSP and nominal full-load efficiency 

for the 50-horsepower, NEMA Design C, 4-pole, enclosed electric motor analyzed. DOE 

purchased only one NEMA Design C electric motor for its tear-down analysis. The remaining 

three CSLs were based on software-modeled electric motors. Therefore, discussion of the NEMA 

Design C revolves around the design changes DOE’s software modeling expert chose to 

implement to increase the efficiency levels of the electric motors. 

DOE achieved the CSL 1 efficiency level by using a higher grade electrical steel and the 

maximum-calculated stack length found by using the method discussed in section 5.4.2. DOE 

then increased the efficiency level to CSL 2 by increasing slot fill and the amount of stator 

copper. To achieve the CSL 3 efficiency level, DOE decreased the slot fill and the amount of 

stator copper but changed the rotor conductor material to die-cast copper.
29

Figure 5.10 NEMA Design C, 50-Horsepower, 4-Pole, Enclosed Motor Engineering 

Analysis Curve

Table 5.21 presents the same engineering analysis results in a tabular form, including the 

nominal full-load efficiency values and the MSPs. Moving from the CSL 0 to CSL 2, DOE 

found that the nominal full-load efficiency would increase 1.5 nominal percentage points over 

the baseline, CSL 0, which represents about a 23 percent reduction in electric motor losses. The 

increase in MSP to move from CSL 0 to CSL 2 is $540, or about a 37 percent increase in MSP 

over CSL 0. To increase from CSL 2 to CSL 3, about a 10 percent reduction in electric motor 

losses, results in an 8.8 percent increase in MSP. 

Table 5.21 Efficiency and Manufacturer Selling Price Data for the NEMA Design C, 50-

Horsepower Motor

CSL Nominal Full-Load Efficiency (%) MSP ($)

0 93.0 1,452

1 94.1 1,664

2 94.5 1,992

3 95.0 2,168

Table 5.22 presents some of the design and performance specifications associated with 

the four 50-horsepower electric motor designs presented above including stator copper weight, 

rotor conductor weight, and electrical steel weight. Table 5.23 shows the NEMA MG1-2009 

Design C performance criteria as well as those design parameters for the software modeled 

electric motors.
30

Table 5.22 NEMA Design C, 50-Horsepower, 4-Pole, Enclosed Motor Characteristics

Parameter Units CSL 0 CSL 1 CSL 2 CSL 3

Efficiency % 93.0 94.1 94.5 95.0

Line Voltage V 460 460 460 460

Full Load Speed RPM 1,770 1,775 1,775 1,782

Full Load Torque lb-ft 148 148 148 147.3

Current A 59.4 63.9 63.7 61.3

Steel - M47 M36 M36 M19

Rotor Conductor Material - Aluminum Aluminum Aluminum Copper

Approximate Slot Fill % 79.6 74.8 85.3 81.3

Stator Wire Gauge AWG 17 17 17 17

Stator Copper Weight lbs 66 78 90 85

Rotor Conductor Weight lbs 16.5 11 11 36.6

Stack Length In 8.67 9.55 9.55 9.55

Frame Weight lbs 125 138 138 138

Table 5.23 NEMA Design C, 50-Horsepower, 4-Pole, Enclosed Motor Modeled 

Characteristics

Parameter Units Design C Limit CSL 1 CSL 2 CSL 3

Efficiency % - 94.1 94.5 95.0

Breakdown Torque % of full-load 190 (min.) 255.2 193.5 233.5

Pull-up Torque % of full-load 150 (min.) 254.8 165.1 202.9

Locked Rotor Torque % of full-load 200 (min.) 254.8 258.6 202.9

Locked Rotor Amps A 362.5 (max.) 353.6 356.2 359.6

5.7 SCALING METHODOLOGY

Due to the large number of equipment classes, DOE was not able to perform a detailed 

engineering analysis on each one. Instead, DOE focused its analysis on three NEMA Design B 

equipment classes and two NEMA Design C equipment classes. From these results, DOE scaled 

to other equipment classes not directly analyzed in the engineering analysis. For the preliminary 

analysis, DOE considered two methods of scaling, one based on the incremental improvement of 

motors losses and one that develops a set of power law equations based on the relationships 

found in the NEMA “Energy Efficient” and NEMA “Premium Efficient”g

5.7.1 Scaling Approach Using Incremental Improvements of Motor Losses

tables of efficiency. 

Ultimately, DOE did not find a large discrepancy between the two methods and elected to use 

the, simpler, incremental improvement of motor losses approach.

Scaling electric motor efficiencies is a complicated proposition that has the potential to 

result in efficiency standards that are not evenly stringent across all equipment classes. Among 

DOE’s three ECGs, there are several hundred combinations of horsepower rating, pole 

 g NEMA MG1-2011 specifies that motors classified as “energy efficient” shall meet or exceed the efficiency values 

listed in Table 12-11 (or Table 20-A for certain larger horsepower ratings). Motors classified as “premium 

efficiency” shall meet or exceed the efficiency values listed in Table 12-12 (or Table 20-B for certain larger 

horsepower ratings).
31

configuration, and enclosure. Within these combinations there is a large number of standardized 

frame number series. Given this sizable number of frame number series, DOE cannot feasibly 

analyze all of these variants – hence, the need for scaling. Scaling across horsepower ratings, 

pole configurations, enclosures, and frame number series is a necessity. For DOE’s first 

approach to scaling, it relied on a relatively simple method of analyzing the motor losses of each 

of its representative units from CSL to CSL and applying those same losses to various segments 

of the market.

As discussed previously, DOE based the first four of its CSLs for ECG 1 on torn-down 

motors. As these motors were marketed and sold with NEMA nominal efficiencies, DOE used 

those values to denote each of those CSLs. Consequently, the efficiency levels that DOE scaled 

to for the non-representative units were also selected from the NEMA nominal efficiency levels. 

DOE also used the NEMA nominal efficiency values for the CSLs that were achieved for the 

representative units using software modeling.

For CSL 1 and CSL 2, DOE only had to do minimal scaling. CSL 1 is based on NEMA 

MG 1-2011 Tables 12-11 and 20-A, which were left unchanged for all electric motors. 

However, Table 12-11 does not specify an efficiency level for 1 horsepower, 2 pole, open 

motors. DOE scaled the missing value by using the same efficiency level as that of 1 

horsepower, 2 pole, enclosed motors. By observing that 1 horsepower, 2 pole, both open and 

enclosed motors had the same Table 12-12 efficiency levels, DOE inferred that the 1 

horsepower, 2 pole, open configuration could also meet the Table 12-11 efficiency level of its 

enclosed counterpart.

CSL 2 is based on NEMA MG 1-2011 Tables 12-12 and 20-B, which specify the nominal 

efficiencies of electric motors that NEMA classifies as “premium efficiency.” The 2011 version 

of NEMA MG1 omits NEMA Premium efficiency levels for 6-pole motors at 300- and 350-

horsepower, leaving a gap in the NEMA Premium efficiency tables where there was no gap in 

the 2009 version of NEMA MG1. To keep CSL 2 continuous from 1- to 500-horsepower, DOE 

scaled the missing values from then next closest horsepower ratings (250- and 400-horsepower). 

Conveniently, the NEMA Premium efficiency levels for 6-pole motors at 250- and 400-

horsepower were equivalent, so DOE assumed that 6-pole motors at 300- and 350-horsepower 

were also at the same efficiency level. 

For the higher CSLs, namely 3, 4, and 5, DOE’s conservation of motor losses approach 

relies on NEMA MG1-2011’s table of nominal efficiencies and the relative improvement in 

motor losses of the representative units. As has been discussed, each incremental improvement 

in NEMA nominal efficiency (or NEMA band) corresponds to roughly a 10 percent reduction in 

motor losses. After CSLs 3, 4, and 5 were developed for each representative unit, DOE applied 

the same reduction in motor losses (or the same number of NEMA band improvements) to 

various segments of the market based on the representative units. DOE assigned a segment of 

the electric motors market, based on horsepower ratings, to each representative unit analyzed. 

DOE’s assignments of these segments of the markets were in part based on the standardized 

NEMA frame number series that NEMA MG1 assigns to horsepower and pole configuration 

combinations. That segmentation of the market is shown in Figure 5.11.
32

Figure 5.11 Segmentation of Electric Motor Market for Representative Units

The first section, shaded blue in Figure 5.11, consists of smaller frame electric motors 

whose efficiencies increase at a quicker rate than larger frame electric motors. A 5-horsepower 

electric motor was selected to represent the electric motors on this section of the graph based on 

high shipment volume and the fact that this electric motor’s efficiency is in middle of this steep 

section of the graph. The electric motors whose analysis is based on the 5-horsepower electric 

motor are electric motors between 1-horsepower and 10-horsepower.

DOE then analyzed the mid-section of the graph, or electric motors whose efficiencies do 

not change as drastically as the blue-shaded region and determined that a 30-horsepower electric 

motor falls in the middle of this region of the graph. Consequently, DOE selected the 30-

horsepower rating to analyze for the red shaded region of the graph, which represents electric 

motors from 15-horsepower to 50-horsepower.

For the third section, DOE observed the electric motor efficiencies exhibited a fairly 

“flat” characteristic as frame sizes increase beyond 60-horsepower. DOE selected a 75-

horsepower electric motor to represent the electric motors on the final part of the graph because 

it was large enough to represent electric motors in this horsepower range yet small enough to 

facilitate various aspects of the engineering analysis, such as physical teardowns of the electric 

motor. The 75-horsepower electric motor represents electric motors on the large end of the scope 

of coverage, from 60-horsepower to 500-horsepower.

In the end, for ECG 1, each CSL above CSL 2 was one NEMA band above the previous 

CSL for each representative unit -- i.e., CSL 3 exceeded Table 12-12 by one band, CSL 4 by 

two, and CSL 5 by three. The following bulleted line items summarize each CSL for ECG 1:

• CSL 0: Lowest-in-scope efficiencies for all equipment classes

• CSL 1: NEMA MG1-2011 Tables 12-11 and 20-A for all equipment classes

• CSL 2: NEMA MG1-2011 Tables 12-12 and 20-Bfor all equipment classes

5 HP

30 HP

75 HP

80.0

82.0

84.0

86.0

88.0

90.0

92.0

94.0

96.0

98.0

100.0

AVerage Efficiency Available (%)

1 to 10 HP 15 to 50 HP 60 to 500 HP
33

• CSL 3: One NEMA band above CSL 1 for all equipment classes

• CSL 4: One NEMA band above CSL 2 for all equipment classes

• CSL 5: One NEMA band above CSL 3 for all equipment classesh

The scaling results for ECG 2 were slightly different. As discussed, there is limited 

equipment selection of NEMA Design C motors, and CSL 0 was the only CSL based on teardown results. Consequently, CSLs 1 through 3 were modeled using a computer software 

program. Relative to the baseline CSL, Table 12-11, DOE was able to achieve a max-tech 

efficiency level that corresponded to an improvement of four NEMA bands for both 

representative units. Going from CSL 0 to the first modeled design for both representative units 

constituted an initial jump of two NEMA bands. Each incremental CSL above CSL 1 

corresponded to a one NEMA band improvement, totaling four NEMA bands of improvement 

relative to the baseline at CSL 3. As the improvements in NEMA bands were the same for both 

representative units, DOE broadly applied these improvements to all equipment classes covered 

by this ECG. The following bullets summarize each CSL for ECG 2.

• CSL 0: NEMA MG1-2011 Table 12-11 for all equipment classes

• CSL 1: Two NEMA bands above CSL 0 for all equipment classes 

• CSL 2: One NEMA band above CSL 1 for all equipment classes

• CSL 3: One NEMA band above CSL 2 for all equipment classes

5.7.2 Scaling Approach Using Regression Equations

DOE developed a second approach for scaling to CSL 3, CSL 4 and CSL 5 which relied 

on regression equations to predict electric motor losses. The first step DOE took in this approach 

was to create a model that describes electric motor losses as a function of the electric motor’s 

rated horsepower. To do this, DOE examined the standards adopted by EISA 2007. For 

polyphase general-purpose electric motors built in a three digit frame size EISA adopted the 

NEMA Premium Standards, shown in NEMA MG 1-2006 in Table 12-12, as the minimum 

efficiency levels. This table has standards for electric motors ranging in horsepower from 1 to 

200-horsepower, in two-, four-, and six-pole configurations, and in open and enclosed 

constructions. DOE plotted this data to observe any trends:

• Electric motor losses (defined as 1 1 − efficiency ) versus horsepower 

If plotted on logarithmic scales, DOE observed that as horsepower increased, electric 

motor losses decreased following a power law function,as shown in Figure 5.12. That is:

• b MotorLosses HP a HP− ( ) = × , where a and b vary by pole configuration and electric 

motor category combination.

 h DOE notes that the segment of the market based on the 30-horsepower NEMA Design B representative unit has the 

same set of nominal efficiencies at CSL 3 and 4 because DOE only developed three CSLs for that representative 

unit.
34

Figure 5.12 NEMA Premium Motor Losses versus Horsepower Rating

As mentioned in section 5.3, for ECG 1 CSL 3 represents a best-in-market efficiency 

level, CSL 5 represents the maximum technology efficiency level, and CSL 4 is an incremental 

efficiency level between the two. For the representative units, the efficiency levels at CSL 3, 

CSL 4 and CSL 5 were already known, either through purchased electric motors or software 

modeling. Therefore, the DOE scaled the CSLs from the representative units to the equipment 

classes that were not analyzed. This was done by using the power law function observed in 

Figure 5.12. Since DOE directly analyzed three horsepower ratings (5-horsepower, 30-

horsepower and 75-horsepower), the electric motor losses continuum was split up into three 

ranges: 1- to 10-horsepower, 15- to 50-horsepower, and 60- to 500-horsepower (as shown in 

Figure 5.11). A power law function was derived for CSL 1 and CSL 2 for each range in the 

representative ECGs as shown in Figure 5.13.

y = 0.2166x-0.261

R2 = 0.9871

y = 0.1705x-0.273

R2 = 0.9868

y = 0.1801x-0.266

R2 = 0.9817

0.01

0.10

1.00

1.0 10.0 100.0

Motor Losses (1/efficiency -1)

Horespower

12-12 Open Motor 2 Pole

12-12 Open Motor 4 Pole

12-12 Open Motor 6 Pole
35

Figure 5.13 Function of Electric Motor Losses with Horsepower for 4-Pole, Enclosed 

Electric Motors

For each range, the exponents of CSL 1 and CSL 2 were averaged to derive the following 

three power law equations:

.286 ( ) − MotorLosses HP = a × HP for 1 horsepower to 10-horsepower

.269 ( ) − MotorLosses HP = a × HP for 15-horsepower to 50-horsepower

.190 ( ) − MotorLosses HP = a × HP for 60-horsepower and greater

where ‘a’ is a constant that that differs for CSL 3, CSL 4 and CSL 5. As previously mentioned, 

the efficiency values for CSL 3, CSL 4 and CSL 5 are known at 5-horsepower, 30-horsepower 

and 75-horsepower as they are the efficiency levels of the representative equipment classes. The 

value of ‘a’ for CSL 3, CSL 4 and CSL 5 can be solved for using these known efficiency values. 

With the constants and exponents derived for the CSL 3, CSL 4 and CSL 5 power functions, the 

equations can be used to derive the CSL 3, CSL 4 and CSL 5 efficiency levels for the unanalyzed 

horsepower ratings. The results of this calculation are shown in Figure 5.14.

CSL 0: y = 0.2135x-0.275

R2 = 0.9412

CSL 0: y = 0.203x-0.262

R2 = 0.8724

CSL 0: y = 0.1434x-0.19

R2 = 0.9198

CSL 1: y = 0.1756x-0.296

R2 = 0.9387

CSL 1: y = 0.1721x-0.276

R2 = 0.979

CSL 1: y = 0.1134x-0.189

R2 = 0.9045

0.01

0.10

1.00

10.00

1.0 10.0 100.0

Motor Losses (1/efficiency -1)

HP

4 Pole - Enclosed Motors

CSL 0

CSL 0

CSL 0

CSL 1

CSL 1

CSL 1

Rep Units

Best Fit (CSL 1)

Best Fit (CSL 1)
36

Figure 5.14 Function of Electric Motor Losses with Horsepower Derived for CSL 2 and 

CSL 3 for 4-Pole, Enclosed Electric Motors of NEMA Design A & B

With CSL3, CSL 4 and CSL 5 determined for the 4-pole enclosed electric motors, DOE 

then had to scale these CSLs to the other electric motor pole configurations and enclosures. To 

do this, DOE compared the efficiencies, at a given horsepower rating, of the 4-pole enclosed 

motors with the efficiencies of other pole configurations and enclosures at the Table 12-12 

levels. The ratio of those efficiencies was multiplied by the scaled efficiency (at CSL 3, 4, or 5) 

of the 4-pole enclosed electric motor efficiency. The resulting product was a scaled efficiency, 

at a given horsepower rating, of the equipment class not analyzed. To do this, DOE had to 

assume that the ratio of efficiencies of different equipment classes at CSL 2stayed constant for 

CSL 3, CSL 4 and CSL 5. The following equation was used to derive the scaled efficiencies:

CSL 0: y = 0.2135x-0.275

R2 = 0.9412

CSL 0: y = 0.203x-0.262

R2 = 0.8724

CSL 0: y = 0.1434x-0.19

R2 = 0.9198

CSL 1: y = 0.1756x-0.296

R2 = 0.9387

CSL 1: y = 0.1721x-0.276

R2 = 0.979

CSL 1: y = 0.1134x-0.189

R2 = 0.9045

0.01

0.10

1.00

1.0 10.0 100.0

Motor Losses (1/efficiency -1)

HP

4 Pole - Enclosed Motors

CSL 0

CSL 0

CSL 0

CSL 1

CSL 1

CSL 1

CSL 2

CSL 3

Rep Units

Best Fit (CSL 1)

Best Fit (CSL 1)

CSL 2: y = 0.1568x-0.286

CSL 3: y = 0.1435x-0.286

CSL 2: y = 0.1456x-0.269

CSL 3: y = 0.1317x-0.269

CSL 2: y = 0.0989x-0.190

CSL 3: y = 0.0890x-0.190
37

( ) ( )

( ) ( ) 4

4

Efficiency hp Efficiency hp

Efficiency hp Efficiency hp E

NP E

NP =

where 

• Efficiency- is the resulting scaled efficiency of the desired equipment class at the new 

CSL (3, 4, or 5).

• EfficiencyNP-is the NEMA Premium efficiency of the desired equipment class.

• EfficiencyNP4E-is the NEMA Premium efficiency of a 4-pole enclosed electric motor.

• Efficiency4E- is the scaled efficiency of a 4-pole enclosed electric motor at the CSL being 

scaled to (3, 4, or 5).

Figure 5.15 Scaling Across Electric Motor Configurations

For example, in order to calculate the efficiency of a 15-horsepower,6-pole, enclosed 

electric motor at CSL 3, see the equation below along with Figure 5.15.

93.0 92.3

92.4

91.7 (15) (15)

(15) (15) 4

4

= E = × =

NP E

NP Efficiency Efficiency

Efficiency Efficiency

As shown above, this method results in an efficiency level of 92.3 percent for a 6-pole 

NEMA Design A or B electric motor of enclosed construction. However, 92.3 percent falls just 

short of the NEMA nominal efficiency (see NEMA MG 1-2009 Table 12-10) of 92.4 percent. 

Therefore, it would have to be “rounded” down to the closest NEMA nominal efficiency level 

which in this case was 91.7 percent. By having to convert the calculated scaled efficiency levels 

to NEMA nominal efficiency levels, DOE observed that some of the efficiency levels that were 

scaled were the same efficiency as the lower CSL. For instance, in the example above CSL 1 

and CSL 2 would be equal to each other at 15-horsepower since the 92.3 percent efficiency 

would have to be rounded down to the closest NEMA nominal efficiency level. As a result, DOE 

elected not to use this as the primary methodology for scaling the engineering results of its 

representative units.

CSL 0 CSL 1 CSL 2 CSL 3 CSL 4 CSL 0 CSL 1 CSL 2 CSL 3 CSL 4

7.5 84.0 89.5 91.7 92.4 93.0 82.5 89.5 91.0

10.0 86.5 89.5 91.7 92.4 93.0 84.0 89.5 91.0

15.0 86.5 91.0 92.4 93.0 93.6 88.5 90.2 91.7 92.4

20.0 87.5 91.0 93.0 93.6 94.1 87.5 90.2 91.7

25.0 89.5 92.4 93.6 94.1 94.5 91.7 91.7 93.0

Efficiency derived from power law equation

Unknown efficiency

6 Pole

Enclosed Frame

HP

4 Pole

Result