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CHAPTER 5. ENGINEERING ANALYSIS

TABLE OF CONTENTS

5.1 INTRODUCTION ........................................................................................................... 5-1

5.2 METHODOLOGY OVERVIEW.................................................................................... 5-2

5.2.1 Cooled Cabinets and Non-Compressor Refrigerators...................................................... 5-2

5.2.2 Ice Makers........................................................................................................................ 5-3

5.3 DATA COLLECTION .................................................................................................... 5-4

5.3.1 Review of Previous Technical Support Documents and Models, Product 

Literature, and Product Databases ................................................................................... 5-4

5.3.2 Energy Tests..................................................................................................................... 5-4

5.3.3 Manufacturer Interviews.................................................................................................. 5-5

5.3.4 Component Vendors ........................................................................................................ 5-5

5.3.5 Reverse Engineering ........................................................................................................ 5-6

5.4 MANUFACTURING COST MODELING..................................................................... 5-9

5.4.1 Generation of Bill of Materials........................................................................................ 5-9

5.4.2 Cost Structure of the Spreadsheet Models....................................................................... 5-9

5.4.3 Cost Model and Definitions........................................................................................... 5-10

5.4.4 Cost Model Assumptions............................................................................................... 5-11

5.4.5 Manufacturing Production Cost..................................................................................... 5-13

5.4.6 Incremental Cost Estimates............................................................................................ 5-14

5.4.7 G&A and Profit.............................................................................................................. 5-15

5.5 ENERGY MODELING................................................................................................. 5-15

5.5.1 ERA Model Overview ................................................................................................... 5-16

5.5.2 Development and Calibration of ERA Models.............................................................. 5-17

5.6 COOLED CABINET AND NON-COMPRESSOR REFRIGERATOR DESIGN 

OPTIONS....................................................................................................................... 5-19

5.6.1 Brushless DC Fan Motors.............................................................................................. 5-19

5.6.2 Insulation Thickness ...................................................................................................... 5-20

5.6.3 Vacuum-Insulated Panels............................................................................................... 5-20

5.6.4 Improved Compressor Efficiency.................................................................................. 5-21

5.6.5 Variable-Speed Compressor .......................................................................................... 5-21

5.6.6 Forced Convection Evaporator ...................................................................................... 5-22

5.6.7 Improved Glass Door Resistivity................................................................................... 5-22

5.6.8 Conversion to Vapor Compression................................................................................ 5-23

5.6.9 Heat Pipe........................................................................................................................ 5-24

5.7 COOLED CABINET ANALYSIS AND RESULTS .................................................... 5-24

5.7.1 CEC-Equivalent Efficiency Level ................................................................................. 5-24

5.7.2 Energy Test Results ....................................................................................................... 5-25

5.7.3 Efficiency Levels........................................................................................................... 5-27

5.7.4 Cooled Cabinet Results.................................................................................................. 5-29
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5.8 NON-COMPRESSOR REFRIGERATOR ANALYSIS AND RESULTS ................... 5-33

5.8.1 Energy Test Results ....................................................................................................... 5-33

5.8.2 Efficiency Levels........................................................................................................... 5-34

5.8.3 Non-Compressor Refrigerator Results........................................................................... 5-35

5.9 ICE MAKER ANALYSIS AND RESULTS................................................................. 5-36

5.9.1 Energy Test Results ....................................................................................................... 5-36

5.9.2 Efficiency Levels........................................................................................................... 5-37

5.9.3 Ice Maker Results .......................................................................................................... 5-39

5.10 HYBRID REFRIGERATION PRODUCTS ANALYSIS AND RESULTS................. 5-40

5.10.1 Comparison of Hybrid and Conventional Refrigeration Products................................. 5-40

5.10.2 Analysis Approach......................................................................................................... 5-42

5.10.3 Results............................................................................................................................ 5-45

REFERENCES .......................................................................................................................... 5-47

LIST OF TABLES

Table 5.1 Cost Model In-House Manufacturing Operation Assumptions................................. 5-12

Table 5.2 Factory Parameter Assumptions................................................................................ 5-12

Table 5.3 Comparison of ERA Results and Test Results for Vapor-Compression Cooled 

Cabinets.............................................................................................................. 5-18

Table 5.4 Design Options .......................................................................................................... 5-19

Table 5.5 Glass Door Design Options ....................................................................................... 5-23

Table 5.6 Cooled Cabinet CEC-Equivalent Efficiency Level Energy Consumption ................ 5-25

Table 5.7 Vapor-Compression Cooled Cabinet Energy Ratings vs. Test Results..................... 5-26

Table 5.8 Non-Compressor Cooled Cabinet Tested Energy Use .............................................. 5-26

Table 5.9 Cooled Cabinet Efficiency Levels............................................................................. 5-28

Table 5.10 Cooled Cabinet Efficiency Levels and Design Options .......................................... 5-29

Table 5.11 6 ft3 Cooled Cabinet Efficiency Levels.................................................................... 5-30

Table 5.12 Incremental Manufacturer Selling Price (MSP) for 6 ft3 Cooled Cabinets.............. 5-30

Table 5.13 2 ft3 Cooled Cabinets Efficiency Levels.................................................................. 5-32

Table 5.14 Incremental Manufacturer Selling Price (MSP) for 2 ft3 Cooled Cabinets.............. 5-32

Table 5.15 Non-Compressor Refrigerator Energy Test Results................................................ 5-33

Table 5.16 Baseline and Max-Available Non-Compressor Refrigerator Efficiency Levels..... 5-34

Table 5.17 Non-Compressor Refrigerator Efficiency Levels and Design Options................... 5-35

Table 5.18 Incremental MSP for Non-Compressor Refrigerators............................................. 5-36

Table 5.19 Ice Maker Test Results ............................................................................................ 5-36

Table 5.20 Portable Ice Maker Efficiency Levels ..................................................................... 5-37

Table 5.21 Cooled-Storage Ice Maker Efficiency Levels.......................................................... 5-38

Table 5.22 Uncooled-Storage Ice Maker Efficiency Levels...................................................... 5-38

Table 5.23 Incremental Manufacturer Selling Price Results for Portable Ice Makers .............. 5-39

Table 5.24 Incremental Manufacturer Selling Price Results for Cooled-Storage Ice 

Makers................................................................................................................ 5-39
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Table 5.25 Incremental Manufacturer Selling Price Results for Uncooled-Storage Ice 

Makers................................................................................................................ 5-40

Table 5.26 Hybrid Product Configuration ................................................................................. 5-43

Table 5.27 Design Options Analyzed for Hybrid Products....................................................... 5-43

Table 5.28 Hybrid Refrigeration Product Design Changes....................................................... 5-46

LIST OF FIGURES

Figure 5.2.1 Flow Diagram of Engineering Analysis Methodology ........................................... 5-3

Figure 5.3.1 Vapor-Compression Cooled Cabinets Selected for Teardown................................ 5-7

Figure 5.4.1 Manufacturing Cost Assessment Stages.................................................................. 5-9

Figure 5.4.2 Full Production Costs............................................................................................ 5-14
5-1

CHAPTER 5. ENGINEERING ANALYSIS

5.1 INTRODUCTION

The engineering analysis establishes the relationship between manufacturer production 

cost (MPC) and energy consumption for the products covered in this rulemaking. The “costefficiency” relationship serves as the basis for cost-benefit calculations for individual customers 

and the Nation. From these calculations, DOE determines the most economically justified and

technologically feasible standard level. 

The inputs to the engineering analysis include baseline unit specifications from the 

market and technology assessment (Chapter 3 of this preliminary technical support document 

(TSD)), the design options from the screening analysis (Chapter 4 of the preliminary TSD), as 

well as cost and energy use data collected from manufacturers, component vendors, reverse

engineering, and energy testing. The output of the engineering analysis is the cost-efficiency 

relationship for each product class, which DOE uses in the life-cycle cost and payback period 

analyses (Chapter 8 of the preliminary TSD) as well as the national impact analysis (Chapter 10 

of the preliminary TSD). DOE completed separate engineering analyses for cooled cabinets, noncompressor refrigerators, and ice makers. For hybrid refrigeration products, DOE conducted 

analysis to support an approach in which the standards for these products would be based on the 

existing standards for refrigerators, refrigerator-freezers, and freezers.

DOE typically structures its engineering analysis around one of three methodologies.

These are: (1) the design-option approach, which calculates the incremental costs and energy 

savings of adding specific design options to a baseline model; (2) the efficiency-level approach, 

which calculates the costs of products which are known to have specific energy efficiency levels, 

without specific focus on the particular design options used to achieve those levels; and/or (3) 

the reverse-engineering or cost-assessment approach, which involves a “bottom-up” 

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

engineering teardowns of the product being analyzed. Deciding which methodology to use for 

the engineering analysis depends on the product, the design options under study, and any 

historical data that DOE can utilize.
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In its engineering analyses for cooled cabinets and non-compressor refrigerators, DOE 

adopted a combined efficiency-level/design-option/reverse-engineering approach to developing 

cost-efficiency curves. For ice makers, DOE adopted an efficiency-level approach. However, for

hybrid refrigeration products, DOE recognized that these products are substantially similar in 

design, construction, and operation to the refrigerators, refrigerator-freezers, and freezers for 

which DOE has recently conducted a full set of rulemaking analyses,1 except for the warmer 

compartments that are also part of hybrid products. Rather than conducting a full set of analyses 

for hybrid products, DOE conducted analysis to investigate whether the 2014 standards for 

equivalent refrigerator, refrigerator-freezer, and freezer product classes could be appropriate for 

hybrid refrigeration products. DOE’s analysis for hybrid products is described in section 5.10.

5.2 METHODOLOGY OVERVIEW

This section describes the analytical methodology DOE used in the engineering analysis

for cooled cabinets, non-compressor refrigerators, and ice makers. As mentioned above, DOE’s 

methodology for its analysis for hybrid refrigeration products is described in section 5.10.

DOE conducts engineering analyses on the basis of its test procedures. For the products 

that are the subject of this rulemaking, DOE does not have established test procedures, but has 

issued a Notice of Proposed Rulemaking (NOPR) for test procedures for miscellaneous 

refrigeration products (“2014 MREF TP NOPR”). The engineering analyses for these products 

are based on the test procedures proposed in the 2014 MREF TP NOPR.

5.2.1 Cooled Cabinets and Non-Compressor Refrigerators

DOE adopted a combined efficiency-level/design-option/reverse-engineering approach to 

developing cost-efficiency curves for cooled cabinets. DOE established efficiency levels 

defining annual energy use as a percent of the California Energy Commission (CEC)-equivalent 

energy use. This is the maximum allowable energy use of the CEC energy standards for wine 

chillers, adjusted to account for the fact that DOE’s proposed test procedure (see the 2014 MREF 

TP NOPR) includes a usage adjustment factor that differs from the factor used in the CEC test 

procedure. DOE’s analysis is based on the efficiency improvements associated with groups of 

design options. Also, DOE developed manufacturing cost models based heavily on reverse 

engineering of products to support calculation of the incremental costs associated with 

improvement of efficiency. Figure 5.2.1 presents the steps in the cooled cabinet analysis and 

illustrates how they contributed to developing the cost-efficiency curves. The process began with 

data collection and ended with the incremental cost curve results. 

To develop the analytically derived cost-efficiency curves, DOE collected information 

from various sources on the manufacturing cost and energy use reduction characteristics of each 

of the design options. DOE reviewed product literature, conducted testing and reverse 

engineering of current products, and interviewed component vendors. DOE also conducted 
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interviews with cooled cabinet manufacturers. The engineering questionnaire associated with this 

discussion is reproduced in appendix 5A.

Figure 5.2.1 Flow Diagram of Engineering Analysis Methodology

Cost information from the vendor interviews and engineering questionnaires provided 

input to the manufacturing cost model. DOE determined incremental costs associated with 

specific design options both from vendor information and using the cost model. DOE modeled 

energy use reduction using the Efficient Refrigerator Analysis (ERA) program developed for the 

2011 residential refrigeration products rulemaking. The test results, reverse engineering, vendor 

interviews, and manufacturer interviews provided input for the energy analysis. The incremental 

cost estimates and the energy modeling results together constitute the cost-efficiency curves for 

cooled cabinets and non-compressor refrigerators presented in this chapter.

5.2.2 Ice Makers

For ice makers, DOE utilized the efficiency-level approach, which calculates the relative 

costs of achieving increases in energy efficiency levels, without focus on to the particular design 

options used to achieve such increases. DOE developed costs for designs representing 

different efficiency levels using information sources and processes similar to those 

described above for cooled cabinets and non-compressor refrigerators. Efficiency levels for 

the analysis were based on energy test results for representative models of ice makers using 

the test procedure proposed in the 2014 MREF TP NOPR. 
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5.3 DATA COLLECTION

DOE collected data from a number of sources to support the engineering analysis. The 

key sources include the following:

• Review of Previous Rulemaking TSDs, Product Literature, and Product Databases

• Energy Tests

• Manufacturer Interviews

• Component Vendors

• Reverse Engineering

The data collection process is described in greater detail in the following sections.

5.3.1 Review of Previous Technical Support Documents and Models, Product Literature, 

and Product Databases

DOE reviewed the 2011 residential refrigeration products rulemaking TSD and its 

associated spreadsheet models to assess their applicability to the current standard-setting process 

for miscellaneous refrigeration products. This previous rulemaking TSD served as a resource for 

design options and energy consumption analysis.

In collecting energy consumption information and other product characteristics, DOE 

reviewed product literature from the websites of miscellaneous refrigeration product 

manufacturers. Because wine chillers are regulated products in California and Canada, DOE also 

consulted the databases of products certified to the CEC2 and Natural Resources Canada 

(NRCan)3 to obtain energy use information for wine chillers (cooled cabinets).

5.3.2 Energy Tests

DOE conducted energy testing on cooled cabinets, non-compressor refrigerators, and ice 

makers to verify the energy use of the products obtained for reverse engineering and to provide 

refrigeration system data to support energy use modeling. These tests served as the only source 

of energy consumption information for non-compressor refrigerators and ice makers, because 

DOE proposed test procedures for these products that have not been used previously. The 

proposed test procedure for non-compressor refrigerators is similar to the existing refrigerator 

test procedure. In addition to the energy use required to produce ice, the proposed test procedure 

for ice makers includes the energy use associated with idle periods when ice is being stored but 

not used, including the energy use associated either with keeping the ice storage bin cold or with 

replenishing melted ice.

DOE contracted with an independent test lab to have tests conducted according to the test 

procedures proposed in the 2014 MREF TP NOPR. In addition to providing measurements of 
5-5

energy consumption, DOE requested specific temperature measurements to be made in various 

locations during the test to better understand the refrigeration system operating characteristics. 

Specifically, low-mass thermocouples were mounted in good thermal contact with the surface of 

refrigerant tubing or thermoelectric components, insulated externally from local ambient air in 

order to represent key refrigeration system temperatures.

5.3.3 Manufacturer Interviews

DOE’s contractor discussed engineering issues with manufacturers of miscellaneous

refrigeration products during the preliminary analysis interviews. DOE conducted these 

engineering discussions using an engineering questionnaire, shown in appendix 5A, which 

guided the interview process. Key technical topics addressed during these discussions include the 

following: 

• Typical characteristics of components and typical design details (i.e., insulation 

thicknesses) used for each product type. 

• Typical design differences between baseline and high-efficiency products. 

• Viability and typical costs of technology options. 

During the interviews, DOE also gathered information about the capital expenditures 

required to increase the efficiency of the baseline units to higher efficiency levels. The 

interviews provided information about the magnitude and the nature of the required capital 

investments. DOE also requested information about the depreciation method used to expense the 

conversion capital.

All of these interviews were conducted under non-disclosure agreements with the 

participating manufacturers. Hence, none of the individual responses can be reported. However, 

values for many of the parameters and costs used in the engineering analysis were based on 

aggregated input from these discussions. Additionally, after developing initial engineering cost 

curves, DOE asked manufacturers to provide feedback on the initial results of its cooled cabinet 

analysis. DOE adjusted its results based on this feedback.

5.3.4 Component Vendors

DOE also contacted major suppliers of key refrigeration product components to obtain 

performance and cost data to support its design option analysis. This vendor solicitation effort 

consisted of phone interviews, email correspondence, and in-person interviews. DOE considered 

the information collected in developing key input parameters for manufacturing cost and energy 

models.
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5.3.5 Reverse Engineering

DOE finds that development of accurate cost estimates for a product is significantly 

enhanced by disassembling the product piece-by-piece and estimating the material and labor cost 

of each component using a process commonly called a physical reverse engineering teardown.

DOE purchased a number of representative cooled cabinets, non-compressor refrigerators, and 

ice makers as part of the engineering analysis in order to examine design and fabrication details. 

Data collected from the teardowns were used as input to the manufacturing cost model for all 

three product types, and to the energy use model for cooled cabinets and non-compressor 

refrigerators. This section describes the rationale behind DOE’s selection of products for reverse 

engineering, as well the measurements made to support subsequent modeling. Section 5.4 more 

thoroughly describes the physical teardown process used to support manufacturing cost 

modeling.

5.3.5.1 Selection of Units

In selecting units for teardown, DOE generally attempts to choose products that span the 

full range of efficiency levels for each product class under consideration. Typically, these 

products also come from manufacturers with the largest market shares, and have features that are 

generally representative of the market.

DOE selected wine chillers to serve as representative products for cooled cabinets. 

Because vapor-compression wine chillers have energy consumption information publicly listed 

in the CEC and NRCan databases, DOE used these databases to select eight units that it deemed 

representative of vapor compression cooled cabinets based on the above criteria. Of these eight 

units, one was a small countertop unit (storage volume of ~2 ft3

), five were under-counter units 

(~6 ft3

), and two were large, standard-sized units (~16 ft3). All of these products featured a single 

glass door, and all but the two standard-sized units had a single controlled temperature zone. The 

two standard-size units each had two independently-controlled temperature zones. Figure 5.3.1

plots both the CEC ratings of DOE’s selections and the ratings of the other units in the CEC and 

NRCan wine chiller databases. As evidenced by this plot, DOE’s selected units span a wide 

range of capacity (i.e., storage volume) and a wide range of efficiency levels compared to the 

maximum allowable energy consumption prescribed by the CEC.
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Figure 5.3.1 Vapor-Compression Cooled Cabinets Selected for Teardown

DOE also selected three thermoelectric wine chillers for teardown to serve as 

representative units for its evaluation of thermoelectric cooled cabinets. As explained in the 

Framework Document4 for this rulemaking, the language of the CEC regulations suggests that 

their wine chiller standards apply to thermoelectric wine chillers. However, after the Framework 

meeting, DOE was unable to identify any thermoelectric units in the CEC database, which 

contains a complete list of all the products certified by manufacturers as satisfying the CEC 

energy conservation standards. This suggests that thermoelectric wine chillers may not meet 

California’s energy conservation standards. Moreover, manufacturers noted during the 

framework meeting that the CEC test procedure specifically mentions compressor cycles (see 

chapter 2 of this TSD), which suggests that manufacturers do not consider the CEC standards to 

apply these products. Additionally, because the Canadian wine chiller test procedure specifically 

indicates that it does not apply to thermoelectric wine chillers, the NRCan database does not 

include any thermoelectric units. 

However, DOE selected units from all the major thermoelectric wine chiller 

manufacturers for reverse engineering teardown and testing. DOE still selected units spanning a 

range of sizes (0.6 ft3

, 1 ft3, and 2 ft3) in order to best represent the breadth of products on the 

market. Each of these units featured glass doors, and the 1 ft3 unit featured two independentlycontrolled temperature zones, each with its own door.

DOE was unable to find publicly-available efficiency information for non-compressor 

refrigerators. DOE purchased and tested six models, including five thermoelectric refrigerators 
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and one absorption refrigerator. DOE conducted full reverse-engineering on three of these 

models (two thermoelectric units and the absorption unit) that broadly represented the group of 

products.

Additionally, DOE was unable to find publicly-available efficiency information for most 

ice makers. Although some manufacturers publish energy consumption information for their ice 

makers, these ratings are based on the DOE test procedure for automatic commercial ice makers, 

which differs from the ice maker test proposed by DOE. Therefore, DOE selected two units from 

each product class that it has proposed in Chapter 3 of this TSD: portable ice makers (IM-P), 

cooled-storage ice makers (IM-C), and uncooled-storage ice makers (IM-U). The two products 

selected for each product class had approximately the same advertised harvest rate, and the 

selected products spanned four manufacturers. 

5.3.5.2 Collection of Cooled Cabinet Energy Modeling Data

As discussed in section 5.2.1, DOE developed energy consumption models for cooled 

cabinets, as well as thermal load models for non-compressor refrigerators. DOE used 

measurements and information collected for the cooled cabinets and non-compressor 

refrigerators during the reverse engineering work as input for energy modeling. The following 

paragraphs describe these measurements.

DOE measured component-level power input for fans, where present. For vaporcompression products, DOE also made air flow measurements for all air-cooled condensers 

using a hot wire anemometer. The location of these measurements varied depending on the heat 

exchanger type and configuration. The determination of air flows based on these measurements 

is not very precise, so DOE used this measurement as an indication of air flow trends rather than 

an exact indication of air flow for the various products. 

DOE measured cabinet dimensions, heat exchanger dimensions, and insulation thickness

for the reverse-engineered cooled cabinets. DOE noted condenser details including type, 

configuration, numbers of tubes and fins, dimensions, and other information needed for energy 

modeling. DOE similarly determined the details of evaporators and suction line heat exchangers 

during teardown.

Finally, DOE recorded component manufacturer and model data for key components 

such as compressors, fans, and controls.
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5.4 MANUFACTURING COST MODELING

5.4.1 Generation of Bill of Materials

The end result of each reverse engineering product teardown is a structured bill of 

materials (BOM). Structured BOMs describe each component of a unit, and its relationship to the 

other components, in the estimated order of assembly. The BOMs describe each fabrication and 

assembly operation in detail, including the type of equipment needed (e.g., stamping presses, 

injection molding machines, spot-welders, etc.) and the process cycle times. The result is a 

thorough and explicit model of the production process.

The BOMs incorporate all materials, components, and fasteners, classified as either raw 

materials or purchased parts and assemblies. The classification into raw materials or purchased 

parts is based on DOE’s previous industry experience, recent information in trade publications, 

and discussions with high- and low-volume original equipment manufacturers (OEMs). 

For purchased parts, the purchase price is an estimate based on volume-variable price 

quotations and detailed discussions with suppliers. For parts fabricated in-house, the prices of 

“raw” metals (e.g., tube, sheet metal) are estimated on the basis of 5-year averages. For other 

“raw” materials such as plastic resins, insulation materials, etc., prices are estimated on a currentmarket basis.

5.4.2 Cost Structure of the Spreadsheet Models

The manufacturing cost assessment methodology used is a detailed, component-focused 

technique for rigorously calculating the manufacturing cost of a product (direct materials, direct 

labor and some overhead costs). Figure 5.4.1 shows the three major steps in generating the 

manufacturing cost.

Figure 5.4.1 Manufacturing Cost Assessment Stages

The first step in the manufacturing cost assessment was the creation of a complete and 

structured BOM from the disassembly of the units selected for teardown. The units were 

dismantled, and each part was characterized according to weight, manufacturing processes used, 
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dimensions, material, and quantity. The BOM incorporates all materials, components, and 

fasteners with estimates of raw material costs and purchased part costs. Assumptions on the 

sourcing of parts and in-house fabrication were based on industry experience, information in 

trade publications, and discussions with manufacturers. Interviews and plant visits were 

conducted with manufacturers to ensure accuracy on methodology and pricing.

The last step was to convert this information into dollar values. To perform this task, 

DOE collected information on labor rates, tooling costs, raw material prices, and other factors. 

DOE assumed values for these parameters using internal expertise and confidential information 

available to DOE contractors. 

In summary, DOE assigned costs of labor, materials, and overhead to each part, whether 

purchased or produced in-house. DOE then aggregated single-part costs into major assemblies 

(e.g., heat exchanger assembly, packaging, controls, fan/motor assembly, refrigerant circuit, and 

wiring harnesses) and summarized these costs in a worksheet. 

Design options used in units subject to teardown were noted in the summary sheet of 

each cost model and DOE estimated their costs individually. Thus, various implementations of 

design options can be accommodated, ranging from assemblies that are entirely purchased to 

units that are made entirely from raw materials. Hybrid assemblies, consisting of purchased parts 

and parts made on site, are thus also accommodated.

5.4.3 Cost Model and Definitions

Once DOE disassembled selected units, and identified technologies, DOE created an 

appropriate manufacturing cost model that could translate physical information into 

manufacturing production costs. The cost model is based on production activities and divides 

factory costs into the following categories:

• Materials: Purchased parts (i.e., fan motors, compressors, etc.), raw materials, (i.e., cold 

rolled steel, copper tube, etc.), and indirect materials that are used for processing and 

fabrication.

• Labor: Fabrication, assembly, indirect, and supervisor labor. Fabrication and assembly 

labor cost are burdened with benefits and supervisory costs.

• Overhead: Equipment, tooling, and building depreciation, as well as utilities, equipment 

and tooling maintenance, insurance, and property taxes.

Because there are many different accounting systems and methods to monitor costs, DOE 

defined the above terms as follows:

• Direct material: Purchased parts (outsourced) plus manufactured parts (made in-house 

from raw materials).

• Indirect material: Material used during manufacturing (e.g., welding rods, adhesives).
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• Fabrication labor: Labor associated with in-house piece manufacturing.

• Assembly labor: Labor associated with final assembly.

• Indirect labor: Labor costs that scaled with fabrication and assembly labor. This included 

the cost of technicians, manufacturing engineering support, stocking, etc. that were 

assigned on a span basis.

• Equipment and plant depreciation: Money allocated to pay for initial equipment 

installation and replacement as the production equipment is amortized.

• Tooling depreciation: Cost for initial tooling (including non-recurring engineering and 

debugging of the tools) and tooling replacement as it wears out or is rendered obsolete.

• Building depreciation: Money allocated to pay for the building space and the conveyors 

that feed and/or make up the assembly line.

• Utilities: Electricity, gas, telephones, etc.

• Maintenance: Annual money spent on maintaining tooling and equipment.

• Insurance: Appropriated as a function of unit cost.

• Property Tax: Appropriated as a function of unit cost.

5.4.4 Cost Model Assumptions

As discussed in the previous section, assumptions about manufacturer practices and cost 

structure played an important role in estimating the final product cost. In converting physical 

information about the product into cost information, DOE reconstructed manufacturing processes 

for each component using internal expertise and knowledge of the methods used by the industry. 

DOE used assumptions regarding the manufacturing process parameters (e.g., equipment use, 

labor rates, tooling depreciation, and cost of purchased raw materials) to determine the value of 

each component. DOE then summed the values of the components into assembly costs and, 

finally, the total product cost. The product cost included the material, labor, and overhead costs 

associated with the manufacturing facility. The material costs included both direct and indirect 

materials. The labor costs included fabrication, assembly, indirect, direct, and supervisor labor 

rates, including the associated overhead. The labor costs were determined by the type of product 

manufactured at the factory. Overhead costs included equipment depreciation, tooling 

depreciation, building depreciation, utilities, equipment, tooling maintenance, insurance, 

property, and taxes.

5.4.4.1 Fabrication Estimates

DOE characterized parts based on whether manufacturers purchased them from outside 

suppliers or fabricated them in-house. For purchased parts, DOE estimated the purchase price. 

For fabricated parts, DOE estimated the price of raw materials (e.g., tube, sheet metal) and the 

cost of transforming them into finished parts. Whenever possible, DOE obtained price quotes 

directly from the manufacturers’ suppliers. 
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DOE based the manufacturing operations assumptions on internal expertise, interviews 

with manufacturers, and manufacturing facilities site visits. The major manufacturing processes 

identified and developed for the spreadsheet model are listed in Table 5.1. Fabrication process 

cycle times were estimated and entered into the BOM.

Table 5.1 Cost Model In-House Manufacturing Operation Assumptions

Fabrication Finishing Assembly/Joining Quality Control

Fixturing

Stamping/Pressing

Turret Punch

Tube Forming

Machine

Cutting & Shearing

T-Drill

Tube/Wire Bending

Brazing

Vacuum Forming

Blow Molding

Washing

Painting

Powder Coating

De-Burring

Polishing

Refrigerant Charging

Adhesive Bonding

Spot Welding

Seam Welding

Packaging

Inspecting & Testing

5.4.4.2 Factory Parameters Assumptions

DOE used information gathered from publicly available literature, manufacturer 

interviews, and analysis of common industry practices to formulate factory parameters for each 

type of manufacturer. DOE first made assumptions about a set of preliminary factory parameters 

before the manufacturer interviews. DOE then revised the assumptions using comments and 

information gathered during the interviews. Table 5.2 lists DOE’s assumptions for cooled 

cabinet, non-compressor refrigerator, and ice maker manufacturers.

Table 5.2 Factory Parameter Assumptions

Parameter Cooled Cabinet, Non-Compressor 

Refrigerator, and Ice Maker 

Assumption

Plant Capacity (units/yr) 25,000

Actual Annual Production Volume (units/yr) 20,000

Fabrication Labor Wages ($/hr) $16.00

Fringe Benefits Ratio 0.5
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5.4.4.3 Material Cost Assumptions

DOE determined the cost of raw materials using publicly available information such as 

the American Metals Market,5 interviews with manufacturers, and direct discussions with 

material suppliers. Common metals used in the fabrication of refrigeration products include cold 

rolled steel, stainless steel, copper tubing, and aluminum. There have been large fluctuations in 

metal prices over the last few years. To account for these fluctuations, DOE used a 5-year 

average of metal prices from the Bureau of Labor Statistics Producer Price Indices (PPIs) 

spanning from 2008 to 2013 with an adjustment to 2013 dollars (2013$).6 DOE used the PPIs for 

copper rolling, drawing, and extruding and steel mill products, and made the adjustments to 

2013$ using the gross domestic product implicit price deflator.7 For resins used in the fabrication 

of these refrigeration products, DOE used current resin prices gathered from industry research, 

publications such as Plastics News,8 and interviews with manufacturers.

In order to assure that the raw material prices DOE used in manufacturing cost estimates 

are representative of actual costs paid by OEMs, DOE sent a material cost questionnaire to the 

manufacturers that participated in the technical interviews. 

5.4.4.4 Inflation Adjustment

As discussed further in section 5.6, DOE used some cost data from the 2011 refrigeration 

products rulemaking in developing purchased parts cost estimates for this engineering analysis. 

To adjust these costs from 2011$ to 2013$, DOE multiplied the 2011 costs by a ratio of the 

producer price index (PPI) for each year. For fan motors, this ratio was equal to 1.07, and for 

compressors, it was equal to 1.26.

5.4.5 Manufacturing Production Cost

After finalizing the cost estimate for each teardown unit, DOE prepared a detailed 

summary for relevant components, subassemblies, and processes. The BOM thus details all 

aspects of product costs. DOE totaled the cost of materials, labor, and direct overhead used to 

manufacture a product in order to calculate the manufacturing production cost. Figure 5.4.2

shows the general breakdown of costs associated with manufacturing a product.a

 

a When viewed from the companywide perspective, the sum of all material, labor, and overhead costs equals the 

company’s sales cost, also referred to as the cost of goods sold. 
5-14

Figure 5.4.2 Full Production Costs

The full cost of the product is equal to the manufacturer selling price (MSP) minus 

profits. The full cost includes the MPC and the non-production cost.

5.4.6 Incremental Cost Estimates

Incremental costs were determined for design options and were applied to the estimated 

cost of the baseline-efficiency cooled cabinets, non-compressor refrigerators, and ice makers. 

The approach for estimating the incremental costs varied depending on the design option. Details 

in this calculation that are specific to individual design options are discussed in sections 5.7, 5.8 

and 5.9. Aspects of the incremental cost calculation that were generally applied to multiple 

design options are discussed in this section. 

Many of the design options involve replacement of a current component with a higherefficiency component. For these design options, the increased price paid by the OEM for the new 

component represents the manufacturing cost increase, because other elements of product cost 
5-15

such as overhead and capital expenditures would be insignificantly affected by these design 

changes. The price increases are discussed in section 5.8 by design option. 

For some design changes, calculating the cost impact of the design change required direct 

use of the manufacturing cost model to determine changes to a number of parts. DOE subtracted 

the baseline manufacturing cost from the manufacturing cost of the modified design to determine 

the incremental cost of the design option. DOE used this approach in particular for insulation 

thickness increases.

5.4.7 G&A and Profit

DOE estimated the further addition to the MSP associated with general and 

administrative costs (G&A) and profit for the appliance industry as percentages of MPC for each 

product type. 

For the preliminary analysis, DOE usually develops this manufacturer markup multiplier 

by examining the annual reports and Securities and Exchange Commission (SEC) 10-K filings of 

several major manufacturers. Because the 10-K reports do not provide gross margin information 

at the subsidiary or business unit level, DOE scaled the gross margin figures from the 10-K 

reports by the percentage of the companies’ overall revenue that is attributable to the particular 

product segment containing consumer refrigeration products.

Following preliminary interviews with manufacturers, DOE adjusted market share 

estimates for the industries covered in this rulemaking. Then, using the financial data of several 

publically-traded manufacturers, DOE calculated separate market share-weighted average 

markups for the following product categories: vapor-compression cooled cabinets, thermoelectric 

cooled cabinets and non-compressor refrigerators, and ice makers. The markup for ice makers 

represents all ice maker product classes and has not been separately evaluated for each class. The 

calculated markups are 1.26, 1.22, and 1.23, respectively for vapor-compression cooled cabinets, 

thermoelectric cooled cabinets and non-compressor refrigerators, and ice makers. Markups are 

explained further in Chapter 6 of this TSD.

5.5 ENERGY MODELING

DOE carried out energy modeling of representative cooled cabinets and on design 

variations of these products that included one or more of the efficiency-improving design options 

considered for the engineering analysis. This energy modeling work provided a basis for 

developing estimates of the energy savings potential associated with cooled cabinet design 

configurations for which test data were not available. Energy model inputs, detailed in appendix 

5A, were determined for these products from the data collected during the reverse engineering 

work, described in section 5.3.5.2. Additional data, used both as input and for calibration of

individual product energy models, were provided by energy testing as described in section 5.3.2. 
5-16

The energy modeling results and manufacturing cost modeling results for these designs allowed 

DOE to develop incremental cost estimates for multiple efficiency levels based on the baseline 

product analyzed.

DOE also used energy modeling as part of its engineering analyses for non-compressor 

refrigerators and for hybrid refrigeration products. The analysis methodology for noncompressor refrigerators is described in section 5.8, and the methodology for hybrid refrigeration 

products is described in section 5.10.

DOE used the ERA simulation program to develop the energy models for this rulemaking 

effort. This program has been updated since its use in the 2011 residential refrigeration products 

rulemaking, to include the ability to model glass doors and warmer compartment temperatures. 

Section 5.5.1 describes this model briefly. A more detailed description of the program and its 

recent development is presented in appendix 5B.

5.5.1 ERA Model Overview

ERA is a steady-state energy model that calculates heat leakage into a cabinet and 

determines the energy needed by the refrigeration system to maintain the interior temperatures as 

specified by the user. Total energy used includes the energy from the compressor, fan motor(s), 

defrost heater, and electronic controls, if applicable. See appendix 5B for a detailed explanation 

of the ERA model. 

ERA combined an analysis of the refrigeration load requirements of the cabinet with a 

simulation of the capacity and efficiency of the refrigeration cycle. The DOS version of ERA 

was developed initially under U.S. Environmental Protection Agency (EPA) sponsorship during 

the late 1980s.9

The program and its User’s Manual were first released to the public in 1993, after 

extensive review and comparison against test data, and for a few years were downloadable from 

the EPA website.10 Subsequent to the 1993 final rule, DOE published updated standards for 

refrigerators, refrigerator-freezers and freezers in 1997, becoming effective in 2001. 62 FR 

23102 (April 28, 1997) Analysis carried out in support of the 1997 final rule involved use of the 

final released EPA version of ERA.

The DOS version of ERA was subsequently modified as described in appendix 5B, but 

these revisions were not made available to the public. During the course of the 2011 rulemaking, 

further development of the model was carried out in order to allow use of the model for 

calculation of energy use of modern consumer refrigeration products and to allow a modern 

version of the program to be made available to stakeholders to validate DOE analysis. Key 

modifications made include enhancement of the user interface to a Windows environment, as 

well as many modeling improvements that are described further in the 2011 rulemaking TSD. 
5-17

Additional modifications were made to ERA during the course of this rulemaking in 

order to make it more appropriate for modeling wine chillers rather than just conventional 

refrigeration products. These modifications include the following:

• Ability to set compartment temperatures as warm as 55 °F, the standardized temperature 

set forth in DOE’s proposed test procedure for wine chillers.

• Ability to model glass doors by inputting an overall U-value.

The development history and capabilities of the program are described in more detail in 

appendix 5B.

5.5.2 Development and Calibration of ERA Models

ERA cooled cabinet modeling during the engineering analysis involved the following two

phases:

• Modeling of existing baseline, medium-efficiency, and max-available reverse-engineered 

products based on the current energy test procedure. These three units were used to 

generate the cost-efficiency curve, as described in section 5.6, and were all approximately 

6 ft3 in volume.

• Iterative modeling with multiple series of adjustments to calculate the energy savings that 

can be achieved with different combinations of design options. 

This section focuses on the first phase of the ERA modeling work: establishing models 

for the teardown products based on the proposed energy test procedure. DOE compared the 

teardown product analysis results with energy test data to assure that the models provided

accurate representation of product energy use. This section discusses the creation and calibration 

of the ERA energy models, the metrics which were compared, and the adjustments which were 

made in some cases in order to improve calibration. 

DOE collected input data for energy modeling during the reverse engineering phase of 

the project, as discussed in section 5.3.5.2 above. The energy tests provided additional 

information for certain model input parameters, such as the number of compressor cycles per 

hour. 

DOE created initial energy models and subsequently adjusted them to provide a best 

match with available data for product energy performance from the energy tests of the reverseengineered units (section 5.3.2). In addition to energy use, DOE also used test data on 

compressor running power input, duty cycle, evaporating temperature, and condensing 

temperature to calibrate the models. Because not all ERA input parameters can be determined 

definitively based on available information, some of the inputs were adjusted within reasonable 

ranges in order to provide good matches between model results and other performance 

indicators. 
5-18

DOE estimated the thermal performance of the glass doors found in most cooled cabinets 

using WINDOW 6 software available from Lawrence Berkeley National Laboratory. WINDOW, 

whose software and user manual are publicly available,11 is a Microsoft Windows-based 

computer program used to determine the thermal and optical properties of glazing and window 

systems for residences and buildings. WINDOW is used as part of the process by which 

manufacturers of windows, doors, and skylights certify their products to the National 

Fenestration Rating Council.12 The program has also been used successfully to model the 

thermal performance of glazed surfaces for refrigerated cabinets. DOE input details about each 

cooled cabinet’s glass door, including thickness, number of panes, and presence of low-e coating 

or inert gas insulation, and received the door’s overall U-value (thermal conductance in W/m2-K) 

as an output to use directly in ERA.

In some cases, DOE concluded that ERA was not modeling particular heat exchangers –

specifically, cold-wall evaporators – properly. In these cases, DOE adjusted the calculated 

effective surface area of the heat exchanger upwards to represent heat transfer performance 

different than modeled to achieve more reasonable match of evaporating or condensing 

temperatures, as well as energy use, as measured during energy test work.

Table 5.3 compares the calibrated ERA analysis results for the analyzed baseline, 

medium-efficiency, and max-available cooled cabinets with the energy test results. DOE 

adjusted the modeled energy use of these units consistent with the proposed cooled cabinet test 

procedure by applying the 0.55 correction factor for cooled cabinets (see section 2.3.6 of this 

TSD for further details on this correction factor). The energy consumption results from ERA are 

within one percent of the energy test results.

Table 5.3 Comparison of ERA Results and Test Results for Vapor-Compression Cooled 

Cabinets

Unit

Energy Use 

(kWh/year) Duty Cycle

Average On-Cycle 

Compressor Power

(W)

Tested Modeled Tested Modeled Tested Modeled

Baseline 310 311 0.701 0.650 87 93

Medium-Efficiency 206 206 0.286 0.271 125 130

Max-Available 104 103 0.193 0.219 95 86
5-19

5.6 COOLED CABINET AND NON-COMPRESSOR REFRIGERATOR DESIGN 

OPTIONS

After conducting the screening analysis described in Chapter 4 of this TSD, DOE 

considered the remaining technologies in the design option analysis for cooled cabinets and noncompressor refrigerators. Table 5.4 lists the design options DOE considered for these two 

product types. Following the table is a description of how DOE applied each of the design 

options in the engineering analysis. See Chapter 3 of this TSD for background descriptions of the 

technologies and Chapter 4 of this TSD for an explanation of why some technologies were 

screened out for one product class but not for the other.

Table 5.4 Design Options

Design Option Considered for Cooled 

Cabinets

Considered for NonCompressor Refrigerators

Brushless DC Condenser Fan 

Motor



Conversion to Vapor 

Compression



Heat Pipe 

Increased Insulation Thickness  

Improved Compressor 

Efficiency



Forced-Convection Evaporator 

Improved Glass Door Resistivity 

Variable-Speed Compressor 

Vacuum-Insulated Panels  

5.6.1 Brushless DC Fan Motors

Brushless DC fan motors are more efficient than the shaded pole motors which are often 

used in medium-efficiency cooled cabinets. Consistent with its methodology in the 2011 

refrigeration TSD, DOE assumed a power reduction of 50 percent for brushless DC (BLDC) 

motors as compared with shaded-pole motors.

1

During the 2011 residential refrigeration products rulemaking, DOE obtained incremental 

cost estimates for the switch to brushless DC motors. For cooled cabinets, DOE used an 

incremental cost estimate of $4.40 for evaporator and condenser fans, which is the 2011 

incremental cost estimate for refrigerator evaporator fans inflated to 2013 dollars.1 DOE applied 

this incremental cost estimate for both evaporator and condenser fans.
5-20

5.6.2 Insulation Thickness

Manufacturers stated during discussions that the potential for insulation thickness 

increases is very limited for cooled cabinets, some of which are designed as “built-in” products, 

intended exclusively to be fastened to adjacent cabinetry upon installation. (See 10 CFR 430.2 

for the definition of “built-in” refrigeration products.) Increasing insulation thickness would 

decrease interior volume, increase exterior dimensions, or cause some combination of both. The 

maximum insulation thickness observed during teardown of under-counter and built-in cooled 

cabinets was 2 inches. This suggests that acceptable interior volumes can be maintained in an 

under-counter or built-in cabinet using 2-inch insulation. Hence, DOE considered increases in 

insulation thickness up to this level.

DOE modeled this design option by directly increasing both the insulation thickness and 

the overall cabinet external dimension inputs in its energy model, maintaining interior volume. 

DOE directly calculated the cost increase using its manufacturing cost model.

5.6.3 Vacuum-Insulated Panels

Vacuum-insulated panels (VIPs) increase efficiency by significantly increasing the 

thermal resistivity of the cabinet walls, therefore decreasing heat penetration into the cabinet. 

DOE considered the addition of half-inch thick VIPs to the walls and doors of the cabinet for all 

product classes, in which case the remainder of the insulation thickness would be filled with 

polyurethane foam. The data and approach DOE used to analyze the costs and thermal impacts of 

VIPs are identical to those that it had used in the 2011 rulemaking and are described in the TSD 

for that rulemaking. 

In discussions with manufacturers during the 2011 refrigeration product rulemaking’s 

NOPR phase, DOE learned that different manufacturers had widely varying levels of success in 

applying VIPs to refrigeration products. The levels of performance benefit reported by 

manufacturers ranged roughly from 0 to 100 percent of the levels predicted by the ERA analysis. 

DOE used a performance degradation factor of 50 percent in its analysis to account for this 

variation in experience. However, DOE notes that none of this manufacturer feedback 

specifically addressed cooled cabinets, and that manufacturers indicated that VIPs provide less 

performance enhancement for fresh food compartments than they do for freezer compartments. 

Consequently, the information obtained regarding VIPs may not extend to compartments 

operated at 55  ̊F. DOE requests data showing thermal performance for such compartments using 

VIPs—see the executive summary of this TSD.

DOE used the same methodology and assumptions, with costs inflated from 2011$ to 

2013$, that were used in the 2011 residential refrigeration products rulemaking to calculate the 

VIP costs for cooled cabinets.
5-21

5.6.4 Improved Compressor Efficiency

For cooled cabinets – most of which use compressors with capacities between 300 and 

400 Btu/hr – DOE considered the use of a higher efficiency compressor in place of the baseline 

compressor. DOE acquired performance data from compressor vendors for use in the energy 

analysis, including capacity and power input for the applicable range of combinations of suction 

and discharge pressure conditions. 

As an example of the potential for improvement, wine chillers typically use compressors 

with a rated energy efficiency ratio (EER) of 3.0 to 4.0 Btu/h-W. DOE considered an improved 

EER of 4.9 Btu/h-W, the maximum efficiency available in the above capacity range. This higher 

efficiency compressor would reduce a cooled cabinet’s electricity consumption but still provide 

the same refrigeration capacity as the compressors that are typically being used in current 

models.

During the 2011 refrigeration products rulemaking, DOE received vendor cost estimates 

for higher-efficiency low-capacity compressors. DOE obtained additional information during 

discussions with manufacturers of products which use these compressors. DOE used a 

representative cost estimate of $10 per 1.0 Btu/h-W efficiency improvement in the analysis for 

the 2011 rulemaking for compressors with capacities less than 600 Btu/h.1 For the cooled cabinet 

analysis, DOE increased this cost to $12.60 per 1.0 Btu/h-W to account for inflation.

5.6.5 Variable-Speed Compressor

Variable-speed compressors (VSCs) operate at multiple speeds to allow variation of 

compressor capacity. Currently, many products containing variable-speed technology use 

Embraco VSCs. DOE obtained compressor performance data for the range of sizes of Embraco 

VSCs and used this information in the energy analysis. 

In order to maximize the energy benefit of a VSC, a design needs to address the potential 

increase in energy use associated with longer fan run time. The increase in fan energy use can 

negate much of the reduction in compressor energy use. As a result, it is often necessary to use 

brushless DC fan motors. 

In addition, brushless DC fan motors can operate at different speeds, depending on the 

design configuration. DOE is not aware of brushless DC fan motors designed for 120 VAC 

power input at representative capacities for refrigerator duty that allow adjustment of fan speed, 

although such a design should be viable. Most designs incorporating fan speed control use DCinput power for the fans and require a control system which provides the DC power, and varies it 

to adjust fan speed. DOE’s analysis did not involve optimization of fan speed and power with the 

VSC system.

During the 2011 residential refrigeration products rulemaking, DOE obtained from 

Embraco, and from discussions with refrigeration product manufacturers, estimates of the cost 
5-22

increase for switching to VSCs. An average of the estimates provided by the manufacturers,

weighted by manufacturer market share, was near $56.1 This included the compressor and its 

motor controller, but did not include additional changes which might be required to implement a 

VSC. DOE inflated this to current dollar values and used a $59 cost increase in the analyses. 

Additional costs associated with conversion of a refrigeration system to variable-speed operation 

include a switch to brushless DC fan motors, and the use of a control system sophisticated 

enough to provide adequate or optimized control. 

The Embraco VSC design includes a control system that can be used with a conventional 

mechanical thermostat. This system has been implemented in a commercially available freezer.13

The Embraco control adjusts speed based on the response of the mechanical thermostat. For its 

analysis, DOE considered this approach suitable for cooled cabinets. DOE also considered use of 

brushless DC fan motors necessary when switching to VSCs. However, the DOE analysis 

incorporated a switch to brushless DC fan motors as a design option earlier than VSCs in the 

progressive layering of design options, because brushless DC fan motors are more cost-effective 

than a full conversion to variable speed. DOE also considered the additional standby power 

consumption associated with the electronic control board required for conversions to variablespeed operation. DOE attributed 1.5 W of standby power to these electronic controls. The energy 

model also adjusted the number of cycles per hour when applying a VSC, to reduce the off-cycle 

loss calculated for the refrigeration system.

5.6.6 Forced Convection Evaporator

Many low- and medium-efficiency cooled cabinets feature a flat, vertical roll-bond 

evaporator mounted on the rear cabinet wall. A forced convection evaporator can be more 

efficient than such a roll-bond evaporator, because it enables more effective heat transfer from 

the refrigerant to the cabinet. DOE’s analysis of converting to a forced convection evaporator as 

a design option includes the following design changes: the replacement of a roll-bond or 

coldwall evaporator with a fin-tube evaporator, a fan assembly, and wiring to power the fan, as 

well as the elimination of the roll-bond evaporator plate. In calculating the net incremental cost 

for this conversion, DOE assumed the use of a brushless DC fan motor.

5.6.7 Improved Glass Door Resistivity

Heat loss through the door can account for a substantial portion of the thermal load in 

cooled cabinets, which typically use double-pane glass doors. By improving the resistivity of the 

glass pack, which consists of the glass pane(s) and the air or gas enclosed by the panes, the heat 

transfer through the door can be significantly decreased. DOE examined two different design 

options related to increasing glass door resistivity. The first, which DOE termed the “mediumtech” glass door, consists of a double-pane glass door with low-e coating on both panes and 

argon gas filling the gap between them. To DOE’s knowledge, this is the door technology with 

the highest thermal resistivity available in cooled cabinets that are currently commercially 
5-23

available. The second design option, which DOE termed the “max-tech” glass door, consists of a 

triple-pane glass door with low-e coating and krypton gas filling.

DOE obtained performance metrics for these door design options by modeling them in 

WINDOW 6, as described in section 5.5.2. DOE then used the U-values output by WINDOW as 

a direct input for ERA. The U-values used for the different door designs are presented in Table 

5.5. The inputs used to generate these U-values in WINDOW are described in appendix 5A.

Table 5.5 Glass Door Design Options

Door Design Option Description U-value (W/m2-K)

Baseline 2-pane, no coating, air filling 3.044

Medium-Tech 2-pane, low-e coating, argon filling 1.709

Max-Tech 3-pane, low-e coating, krypton filling 1.143

DOE consulted with glass door manufacturers to obtain cost estimates for these different 

door design options. Based on these discussions, DOE used for its analysis a cost of $100 for a 

4.2 ft2 baseline door, an incremental cost of $12 for the medium-tech door, and an additional 

incremental cost of $18 for the max-tech door, yielding an overall incremental cost of $30 over 

the cost of the baseline door for the max-tech door.

One potential concern of proposing the replacement of a double-pane door with a triplepane door is that the hinges currently used by cooled cabinets may be unable to support the extra 

weight of the additional glass pane. Based on the teardown analysis performed by DOE, a typical 

glass door for a compact-sized cooled cabinet weighs approximately 25 pounds, and the addition 

of a third glass pane would increase the total weight of the door to approximately 31 pounds. 

Moreover, based on DOE’s reverse-engineering analyses, the hinges found on most compact 

cooled cabinet doors are similar in size, composition, and structure to the hinges found on the 

compact refrigerator doors analyzed in the 2011 residential refrigeration rulemaking. Because 

compact refrigerator doors are designed to support the weight of both the door and beverages 

stored in the door’s shelves, DOE does not expect the modest weight addition for a triple-pane 

door to be a significant mechanical design issue for the hinges that would have to support the 

additional weight. Hence, DOE did not use concerns about hinge loads as a reason to reject the 

triple-pane door design option.

5.6.8 Conversion to Vapor Compression

As discussed in Chapter 3 of this TSD, vapor compression is a more efficient 

refrigeration technology than thermoelectric or absorption refrigeration. While, for this 

rulemaking effort, DOE analyzed cooled cabinets at volumes of 2 ft

3 and 6 ft3

, the maximum 

capacity of non-compressor cooled cabinets available for sale was found to be roughly 2 ft3. 

Hence, DOE considered baseline designs using thermoelectric or absorption technology and 
5-24

potential conversion to vapor compression as a design option only for the 2 ft3 cooled cabinet

analysis.

DOE based the cost of converting to vapor-compression refrigeration technology on its 

manufacturing cost models for the refrigeration system in reverse-engineered 2 ft3 cooled 

cabinets – one using thermoelectric, and the other vapor-compression refrigeration technology. 

The calculation included the costs of the heat exchangers, refrigerant tubing, and a baseline 

compressor. DOE estimated this incremental conversion cost as $65.

5.6.9 Heat Pipe

DOE is aware that some thermoelectric refrigerators use a heat pipe to facilitate passive 

heat transfer on the “hot side” of their thermoelectric modules. Therefore, DOE considered the 

addition of a heat pipe as a design option for thermoelectric (non-compressor) refrigerators.

DOE used its manufacturing cost model to estimate the costs associated with the addition 

of a heat pipe. Because DOE’s reverse-engineered unit containing a heat pipe also featured two 

hot-side fans, the calculated incremental costs for the use of a heat pipe, also included the cost of 

a secondary hot-side fan.

5.7 COOLED CABINET ANALYSIS AND RESULTS

As mentioned in section 5.2, DOE adopted a combined efficiency-level/designoption/reverse-engineering approach to developing cost-efficiency curves for cooled cabinets. 

DOE established efficiency levels expressed as percent of CEC-equivalent energy consumption 

(as defined in section 5.7.1). DOE’s analysis is based on the efficiency improvements associated 

with groups of design options (as described in section 5.7.3. Also, DOE developed 

manufacturing cost models based heavily on reverse engineering of products to support 

calculation of the incremental costs associated with improvement of efficiency. The following 

sections describe the details and results of this analysis.

5.7.1 CEC-Equivalent Efficiency Level

DOE’s proposed test procedure for cooled cabinets is almost identical to the wine chiller 

test procedure established by CEC as part of its Title 20 Appliance Efficiency Regulations.14

DOE’s proposed test differs from the CEC test procedure only in the application of a usage 

adjustment factor of 0.55 rather than the 0.85 used by the CEC. Consequently, DOE chose to 

express the baseline, and subsequent efficiency levels as a percentage of the equivalent CEC 

regulation (the CEC wine chiller standards multiplied by 0.55 and divided by 0.85). This 

baseline efficiency level, expressed as annual energy consumption as a function of volume, is

presented in Table 5.6. As explained in Chapter 3, DOE’s cooled cabinet analysis is focused 
5-25

solely on units with automatic, rather than manual, defrost. Therefore, DOE used the CEC 

standard for wine chillers with automatic defrost as the basis for its cooled cabinet baseline 

efficiency level.

Table 5.6 Cooled Cabinet CEC-Equivalent Efficiency Level Energy Consumption

Appliance Baseline Efficiency Level Annual Energy 

Consumption (kWh)

Wine chillers with automatic defrost (0.55/0.85)*(17.4V + 344)

= 11.3V + 223

V = volume in cubic feet.

DOE used this efficiency level as a point of comparison for its energy test results, as 

described in section 5.7.2. In this document, cooled cabinet efficiency is presented as a percent 

of CEC-equivalent energy consumption; in other words, a cooled cabinet which exactly meets

the CEC energy standard has an efficiency level equal to 100 percent. This is called CECequivalent because the energy use in kWh is not the same as that specified by the CEC energy 

standard, due to the use of a different usage adjustment factor for the proposed DOE test. 

Likewise, cooled cabinets with lower energy consumption have efficiency levels that are less 

than 100 percent. DOE chose this approach rather than representing efficiency levels as 

percentages of energy consumption at the baseline, because manufacturers have stated that the 

CEC Standard is a de-facto market baseline. 

5.7.2 Energy Test Results

5.7.2.1 Vapor-Compression Cooled Cabinets

DOE tested and tore down eight vapor-compression wine chillers for its cooled cabinet 

analysis. Of these wine chillers, as described further in section 5.3.5.1, one was a compact 

countertop unit (approximately 2 ft3 of storage volume), five were under-counter units 

(approximately 6 ft3), and two were “standard-sized” units (approximately 16 ft3). As shown in 

Table 5.7 below, the energy use measured for most of these wine chillers was lower than their 

CEC ratings, although one used more energy than its rating.

Table 5.7 also shows the average of the rated and test energy consumption for each 

vapor-compression cooled cabinet. Because of the disparity between the CEC ratings and energy 

test results for many of these units, DOE selected energy use equal to the average of the rating 

and the measurement to represent most of the units for subsequent analysis. Although DOE feels 

that the measurements represent an indication of the potential efficiency level of the product, 

DOE acknowledges that there may be variations in manufacturing and in test results, and is being 

conservative in its use of the average values. Note that the percent of CEC standard levels 

presented for the tested units in the table are identical to their CEC-equivalent efficiency level 

representations in percentages.
5-26

Table 5.7 Vapor-Compression Cooled Cabinet Energy Ratings vs. Test Results

Storage 

Volume 

(ft3)

Rated Energy 

Consumption 

(kWh/year)1

Rated % 

of CEC 

Standard

Tested Energy 

Consumption 

(kWh/year)

Tested % 

of CEC 

Standard

Average 

Energy 

Consumption 

(kWh/year)

Average 

% of

CEC 

Standard

1.7 206 87% 131 54% 167 70%

5.9 229 80% 206 71% 218 75%

5.7 285 99% 310 108% 298 103%

5.4 226 80% 147 52% 187 66%

5.9 284 100% 173 60% 229 80%

5.9 170 60% 104 36% 137 48%

15.4 342 86% 233 59% 288 72%

17.3 243 57% 237 57% 240 57% 1 From the CEC database: http://www.appliances.energy.ca.gov/AdvancedSearch.aspx, adjusted to account for the 

usage factor difference between the CEC test procedure and the proposed DOE test procedure.

5.7.2.1 Non-Compressor Cooled Cabinets

As described in section 5.3.5.1, DOE also tested and reverse engineered three noncompressor (thermoelectric) wine chillers. DOE’s proposed test procedure for non-compressor 

cooled cabinets differs from its proposed test procedure for vapor-compression cooled cabinets 

(and the CEC’s wine chiller test procedure) in that it involves testing at an ambient test 

temperature of 72 °F, rather than 90 °F, and a usage adjustment factor of 1.2, to represent the 

impacts of door openings in field operation at 72 °F. The proposed cooled cabinet test 

procedures are designed to allow direct comparison of test results for vapor-compression and 

non-compressor cooled cabinets, thus allowing use of the CEC-equivalent percentages to 

represent efficiency levels for both types of products.

DOE’s testing shows that the energy use of thermoelectric cooled cabinets can be much 

higher than the CEC-equivalent energy use. As shown in Table 5.8, which displays these test 

results, the percent CEC-equivalent energy use of the three thermoelectric cooled cabinets tested 

by DOE increased with increasing volume. 

Table 5.8 Non-Compressor Cooled Cabinet Tested Energy Use 

Storage Volume (ft3) Tested Energy Consumption 

(kWh/year)

% of CECEquivalent Energy 

Consumption

0.64 142 62%

1.08 439 187%

2.26 663 267%

As described in Chapter 3 of this TSD, DOE is proposing to consider vapor-compression 

and non-compressor cooled cabinets in the same product class. 
5-27

DOE developed cost-efficiency curves for 2 ft3 and 6 ft3 cooled cabinets. Because DOE is 

not aware of any non-compressor cooled cabinet products significantly larger than 2 ft3, the 6 

ft3

analysis does not consider efficiency levels associated with non-compressor refrigeration 

technology.

5.7.2.1 Active Defrost Cooled Cabinets

DOE initially considered establishing a separate product class for cooled cabinets with 

active heater defrost (as opposed to passive, or off-cycle, defrost). As mentioned in Chapter 3, 

DOE is not aware of many cooled cabinets that have such active defrost. DOE tested one such

unit in order to determine the contribution of the active defrost feature to the overall energy 

consumption of the unit. The test results showed that the defrost heater accounted for 

approximately 1.5 percent of the product’s overall energy consumption. This relatively small 

contribution, combined with DOE’s conclusion that such units represent a very small portion of 

the overall cooled cabinet market, has led DOE to analyze active defrost cooled cabinets in the 

same product class as passive defrost cooled cabinets, as noted in Chapter 3 of this TSD. 

5.7.3 Efficiency Levels

When proposing efficiency levels for products, DOE first selects a baseline efficiency 

level as a reference point, against which DOE measures changes resulting from the 

implementation of energy-saving design options. The baseline efficiency level for each product 

type represents the efficiency associated with the basic characteristics of products in that 

category. Typically, a baseline efficiency level is equal to the current required energy 

conservation standard. However, because there are currently no federal energy conservation 

standards for cooled cabinets, DOE selected a baseline efficiency level that reflects the leastefficient product evaluated.

DOE analyzed efficiency levels (ELs) that spanned the range of energy consumption 

observed from all available data, as described further in Chapter 7 of this TSD. The lowest 

efficiency that it observed, which DOE called EL 0, was 267 percent of the CEC-equivalent 

energy consumption as defined in section 5.7.1. The highest efficiency level that it considered, 

which DOE called EL 11, was 32 percent of the CEC-equivalent energy consumption. The range 

of ELs that DOE considered in its analysis is presented in Table 5.9. In this table, all other 

efficiency levels are compared to EL4 – the efficiency level which represents the energy 

consumption equivalent to the current CEC Standard. More information on the selection of EL4 

to compare other levels against can be found in Chapter 2 of this TSD.
5-28

Table 5.9 Cooled Cabinet Efficiency Levels

Efficiency Level Percent of CEC-Equivalent Energy Consumption

EL 0 267%

EL 1 200%

EL 2 160%

EL 3 130%

EL 4 (CEC-Equivalent) 100%

EL 5 90%

EL 6 80%

EL 7 70%

EL 8 60%

EL 9 50%

EL 10 40%

EL 11 (Max-Tech) 32%

EL 11 represents the maximum technology (max-tech) efficiency level for cooled 

cabinets. DOE defines a max-tech level to represent the theoretical maximum possible efficiency 

if all available design options are incorporated. The max-tech level may not be the same as the 

maximum available level, which is the highest efficiency unit currently available on the market. 

Moreover, it is possible that products at the max-tech level are not commercially available,

because it may not be economically feasible to produce them at the present time. 

DOE determined the max-tech level for cooled cabinets using energy modeling. The 

energy model for the maximum technology level was based on use of all design options 

applicable for cooled cabinets. While this product configuration has not likely been tested as a 

prototype, all of the individual design options have been incorporated in available products. The 

design options associated with the max-tech efficiency level for cooled cabinets are summarized

in Table 5.10 below, as are the design options associated with the CEC-equivalent, mediumefficiency, and maximum-available units. This max-tech efficiency level is more efficient (has 

lower energy use) than that of the maximum available products. The costs of the max-tech 

efficiency level design options are also quite high, as they are based on extensive use of highcost design options such as vacuum insulating panels as well as all applicable lower-cost design 

options. Details describing how DOE modeled the cost and efficiency impacts of these design 

options can be found in section 5.6. Further details about each of the units used to develop the 

cost-efficiency curve can be found in appendix 5A.
5-29

Table 5.10 Cooled Cabinet Efficiency Levels and Design Options

Efficiency 

Level 

Designation

CECEquivalentMediumEfficiency Max-Available Max-Tech 

Percent of 

CECEquivalent 

Energy Use

100% 75% 48% 32%

Condenser 

Fan Motor

SPM SPM SPM BLDC 

Insulation 

Thickness

1.75” on top 

and rear, 1.5” 

on sides and 

bottom

1.5” on top, sides, 

and rear, 2” on 

bottom

2” on all surfaces 2” thick on all 

surfaces

VacuumInsulated 

Panels

None None None

VIPs on half the 

cabinet’s surface 

area

Compressor 3.0 EER 3.2 EER 4.9 EER Variable-speed

Evaporator Coldwall Roll-bond Roll-bond with 

fan

Round-Tube, Flat 

Fin, Forcedconvection

Glass Door

Baseline 

(dual-pane, no 

low-e coating 

or inert gas 

filling)

Baseline (dualpane, no low-e 

coating or inert 

gas filling)

Medium-tech 

(dual-pane, low-e 

coating, argonfilled)

Max-tech (triplepane, low-e coated, 

krypton-filled)

5.7.4 Cooled Cabinet Results

DOE developed cost-efficiency curves for both 6 ft3 and 2 ft3 cooled cabinets. These costefficiency curves are presented in the following sections.

5.7.4.1 Six Cubic Foot Cooled Cabinets

To develop a cost-efficiency curve for cooled cabinets, DOE selected three of its reverseengineered vapor-compression units of capacity equal to 6 ft3 and determined the costs of the 

groups of design options associated with the efficiency improvements of each unit. The 

efficiency levels analyzed for the 6 ft3 cooled cabinet analysis represent the CEC-equivalent

efficiency level, medium efficiency, and max-available efficiency levels, as shown in Table 5.11

The first three levels represent tested and reverse-engineered cooled cabinets. The fourth level 

represents the max-tech efficiency level described in section 5.7.3. The incremental MSPs are 
5-30

equal to the markup factor, 1.26 for vapor-compression cooled cabinets (see section 5.4.7), 

multiplied by the MPC.

Table 5.11 6 ft3 Cooled Cabinet Efficiency Levels

Efficiency Level 

Description

Energy 

Consumption 

(kWh/year)

% of CEC 

Equivalent Energy 

Consumption

Incremental 

MPC

Incremental 

MSP

CEC-Equivalent 298 100% $0 $0

MediumEfficiency 229 75% $25 $31

Max-Available 137 48% $65 $82

Max-Tech* 93 32% $204 $258

* Note: This does not represent an actual unit.

DOE calculated its cost-efficiency curve for 6 ft3 cooled cabinets using these four points. 

For intermediate efficiency levels between those represented by these four points, DOE 

interpolated the associated incremental costs. For example, the incremental MSP for EL 7 at 70% 

is equal to the incremental cost for the medium efficiency level (i.e., $31) plus 5/27 times the 

MPC increase between the medium and max-available levels, i.e., $31 + (5/27)*($82-$31) = 

$41. DOE believes that the selected intermediate efficiency levels should be achievable designs

based on partial application of the design options (e.g., increased insulation thickness). DOE did 

not include ELs 0 through 3 in this cost-efficiency curve because it is not aware of any 6 ft3

cooled cabinets at those efficiency levels. Hence, the incremental costs associated with these ELs 

less than EL4 are all zero. The cost-efficiency curve for 6 ft3 cooled-cabinets is summarized in 

Table 5.12 below. 

Table 5.12 Incremental Manufacturer Selling Price (MSP) for 6 ft3 Cooled Cabinets

Efficiency Level

(Percent of CEC-Equivalent Energy Consumption)

Incremental

MSP

EL 0 (267%) $0

EL 1 (200%) $0

EL 2 (160%) $0

EL 3 (130%) $0

EL 4 (100% -- CEC-Equivalent) $0

EL 5 (90%) $15

EL 6 (80%) $26

EL 7 (70%) $41

EL 8 (60%) $59

EL 9 (50%) $78

EL 10 (40%) $170

EL 11 (32% -- Max-Tech) $258
5-31

5.7.4.2 Two Cubic Foot Cooled Cabinets

DOE developed analysis for 2 ft3 cooled cabinets to represent lower-capacity cooled 

cabinets. Products of this size are available using vapor-compression, thermoelectric, and 

absorption refrigeration technologies. Hence, DOE’s analysis for this capacity considered 

efficiency levels representing greater energy use than the CEC-equivalent efficiency level. The 

least-cost/highest energy use considered for this analysis, called “baseline thermoelectric”, 

represents 267 percent of the CEC-equivalent efficiency level

The first point on the 2 ft3 cost-efficiency curve represents the tested energy use of a 

reverse-engineered 2 ft3 thermoelectric unit. The second point on this curve represents a reverseengineered 2 ft3 vapor-compression unit. The incremental cost associated with this second unit 

include the costs of increasing insulation thickness and converting the thermoelectric 

refrigeration system to a vapor-compression refrigeration system, as described in section 5.6.8. 

Finally, the efficiency levels of the medium-efficiency, max-available, and max-tech points 

correspond to the equivalent levels in the 6 ft3 curve, although the incremental costs associated 

with these efficiency levels are lower due to the unit’s smaller size. For design options affected 

by the cabinet size, DOE calculated the costs required to implement such design options for a 

smaller unit. 

DOE used its manufacturing cost model to calculate the cost of increased insulation 

thickness and a supplemental spreadsheet model to calculate the cost of vacuum-insulated panels 

for smaller units. DOE also adjusted its glass door costs to account for the smaller door area of a 

2 ft3 unit. The remaining design options are related to the refrigeration system, which is sized 

depending on the capacity of the compressor. As discussed in Chapter 3 of this TSD, compressor 

efficiency drops off significantly as capacity decreases. Because 6 ft3 cooled cabinets already use 

the smallest-capacity compressors available on the market today at high EERs, 2 ft3 units would 

use the same compressors and thus heat exchanger and fan size would not be reduced. 

Consequently, the incremental costs for improved compressors, evaporators, and condenser fan 

motors for the 2 ft3 analysis are equal to the equivalent incremental costs of the 6 ft3 analysis.

The efficiency levels of 2 ft3 cooled cabinet analysis are presented in Table 5.13. The incremental 

MSPs are equal to the markup factor, 1.22 for thermoelectric cooled cabinets (see section 5.4.7), 

multiplied by the MPC.
5-32

Table 5.13 2 ft3 Cooled Cabinets Efficiency Levels

Efficiency Level

Description

Energy 

Consumption 

(kWh/year)

% of CECEquivalent 

Energy 

Consumption

Incremental 

MPC

Incremental 

MSP

Baseline 

Thermoelectric

663 267% $0 $0

Low-Efficiency 

Vapor 

Compression

167 87% $58 $71

MediumEfficiency145 75% $82 $100

Max-Available 92 48% $115 $140

Max-Tech 61 32% $225 $275

DOE calculated its cost-efficiency curve for 2 ft3 cooled cabinets using the five efficiency 

levels presented in Table 5.13, using an interpolation approach, as discussed above for the 6 ft3

cooled cabinets. The incremental MSP costs for 2 ft3 cooled-cabinets are presented in Table 5.14

below. 

Table 5.14 Incremental Manufacturer Selling Price (MSP) for 2 ft3 Cooled Cabinets

Efficiency Level

(Percent of CEC-Equivalent

Energy Consumption)

Incremental MSP

EL 0 (267%) $0

EL 1 (200%) $26

EL 2 (160% $42

EL 3 (130%) $54

EL 4 (100% -- CEC Equivalent) $66

EL 5 (90%) $70

EL 6 (80%) $88

EL 7 (70%) $107

EL 8 (60%) $122

EL 9 (50%) $137

EL 10 (40%) $207

EL 11 (32% -- Max-Tech) $275
5-33

5.8 NON-COMPRESSOR REFRIGERATOR ANALYSIS AND RESULTS

DOE used a combined efficiency level/design option/reverse engineering approach to 

develop cost-efficiency curves for non-compressor refrigerators. DOE established efficiency 

levels defined as percent of baseline energy consumption. DOE’s analysis is based on the 

efficiency improvements associated with groups of design options. Also, DOE used 

manufacturing cost models based on reverse engineering of products to calculate the incremental 

costs associated with efficiency improvements. The following sections describe the details and 

results of this analysis.

5.8.1 Energy Test Results

DOE tested seven thermoelectric refrigerators representing five models, testing two units 

each of two of these models. DOE reverse-engineered two of the models. These thermoelectric 

refrigerators ranged in capacity from 0.25 ft3 to 1.7 ft3. DOE also tested and reverse-engineered 

one 1.2 ft3 absorption refrigerator. Not one of the tested units achieved the 39 °F standardized 

temperature for fresh food compartments when tested in the 90 °F ambient temperature required 

by DOE’s proposed test procedure for non-compressor refrigerators (see the 2014 MREF TP 

NOPR). DOE calculated the annual energy consumption of the products using the proposed test 

procedure, which would require rating based on their coldest temperature setting. The results of 

these energy tests are presented in Table 5.15.

Table 5.15 Non-Compressor Refrigerator Energy Test Results

Unit Volume (ft3) Compartment Temperature 

Measured for Cold Setting (°F)

Measured Energy Use1 

(kWh/year)

TE2 1, Unit 1 1.7 55.4 578

TE 1, Unit 2 1.7 58.2 559

TE 2, Unit 1 1.7 42.8 622

TE 2, Unit 2 1.7 48.2 596

TE 3 1.6 48.6 832

TE 4 0.87 57.5 565

TE 5 0.25 61.1 451

ABS2 1 1.2 52.6 569

1

Measured for operation in the cold temperature setting, consistent with the proposed test 

procedure (see 2014 MREF TP NOPR). 2

“TE” refers to thermoelectric refrigerators, while “ABS” refers to absorption refrigerators.
5-34

5.8.2 Efficiency Levels

5.8.2.1 Efficiency Levels Corresponding to Reverse-Engineered Units

Because there are no current federal, state, or voluntary industry energy conservation 

standards for non-compressor refrigerators, and because they have no established test procedure, 

there is no established baseline efficiency level for these products. Therefore, DOE developed its 

analysis based on the energy test results in Table 5.15, selecting both a baseline and a maxavailable unit to feature in its cost-efficiency curve. 

DOE reverse-engineered two products of 1.7 ft3 storage volume, which DOE found to be 

most representative of the size of non-compressor refrigerators on the market. Because DOE 

tested two models of each of these units, DOE selected for its analysis the energy test results 

associated with the coldest storage temperature achieved by each unit. DOE divided the energy 

use of the reverse-engineered unit with the highest energy consumption by its standard 

adjustment factor (discussed in Chapter 2 of this TSD) to determine the baseline efficiency level 

for its non-compressor refrigerator analysis. In order to determine efficiency level of any given 

unit, DOE multiplied the baseline efficiency level by the standard adjustment factor for the unit 

to determine the adjusted baseline energy use. The energy consumption, coldest storage 

temperature, and efficiency of these two units are shown in Table 5.16.

Table 5.16 Baseline and Max-Available Non-Compressor Refrigerator Efficiency Levels

Unit Volume 

(ft3

)

Compartment

Temperature 

Measured for 

Cold Setting 

(°F)

Standard 

Adjustment 

Factor

(90 –

TTest_Cold)/ 

(90-39)

Measured 

Energy Use 

(kWh/year)

Adjusted 

Baseline 

Energy 

Use

Percent of 

Baseline 

Energy Use

Baseline 1.7 55.4 0.68 578 578 100%

MaxAvailable 1.7 42.8 0.93 622 791 79%

The baseline efficiency level corresponding to 39  ̊F compartment temperature is calculated as 

the energy use of the baseline unit divided by the standard adjustment factor calculated for this 

unit, i.e., 578 ÷ 0.68 = 850. The adjusted baseline energy use for a cold-setting compartment 

temperature is equal to the baseline efficiency level multiplied by the standard adjustment factor.

5.8.2.2 Efficiency Levels Corresponding to Hypothetical Units

The design of the max-available unit differs from that of the baseline unit in two ways—

it has thicker insulation and uses heat pipe to facilitate heat transfer from the hot side of the 

thermoelectric module to the ambient air. DOE developed a cost-efficiency curve that also 

considered levels of insulation thickness different than those of the tested units. DOE used ERA 
5-35

to calculate the thermal load associated with each configuration considered in the analysis. DOE 

also used energy modeling to determine a maximum-technology efficiency level for noncompressor refrigerators using vacuum-insulated panels on half of the unit’s surface area. Table 

5.17 summarizes the efficiency levels that DOE analyzed, indicating which design options 

correspond to the different efficiency levels.

DOE analyzed incremental ELs that spanned the range of energy consumption observed 

from all available data, as presented in Table 5.17. The lowest efficiency that it observed, which 

DOE called EL 0, was 100 percent of the baseline unit’s energy consumption. DOE calculated 

costs for efficiency levels in 5 percent increments by interpolating between the efficiency levels 

of the analyzed designs. DOE believes that the intermediate ELs are possible through partial 

adoption of the design options.

Table 5.17 Non-Compressor Refrigerator Efficiency Levels and Design Options

Baseline 

Unit

Baseline with 

Max-Available 

Insulation*

Max-Available 

Unit

MaxAvailable 

with Added 

Insulation*

Max-Tech

Efficiency 

Level*

Efficiency 

Level 100% 82% 79% 67% 64%

Insulation 

Thickness

1.25” on all 

sides, 1” on 

door

1.5” on all 

sides, 2.5” on 

door

1.5” on all 

sides, 2.5” on 

door

2” on all 

sides, 2.5” 

on door

2” on all sides, 

2.5” on door

Heat Pipe None None Present Present Present

VacuumInsulated 

Panels

None None None None

VIPs on half the 

cabinet’s 

surface area

* Note: These do not represent actual models.

5.8.3 Non-Compressor Refrigerator Results

The incremental MSPs for non-compressor refrigerators are presented in Table 5.18

below.
5-36

Table 5.18 Incremental MSP for Non-Compressor Refrigerators

Efficiency Level (percent of baseline energy use) Total Added MSP

EL 0 (100% – Baseline) $0

EL 1 (95%) $0.27

EL 2 (90%) $0.53

EL 3 (85%) $0.80

EL 4 (80%) $10.45

EL 5 (75%) $16.93

EL 6 (70%) $17.33

EL 7 (65%) $27.38

EL 8 (64% – Max-Tech) $35.59

5.9 ICE MAKER ANALYSIS AND RESULTS

DOE conducted engineering analysis for ice makers using an efficiency-level approach, 

which calculates the relative costs of achieving increases in energy efficiency levels without 

regard to the particular design options used to achieve such increases. The following sections 

describe this analysis.

5.9.1 Energy Test Results

DOE tested and reverse engineered two ice makers in each of its three proposed product 

classes: portable ice makers (IM-P), cooled-storage ice makers (IM-C), and uncooled-storage ice 

makers (IM-U). These six units were tested using the ice maker test procedure proposed in the 

2014 MREF TP NOPR. This test measures the energy use associated with icemaking to serve a 

daily ice usage of 4 pounds per day and also with maintaining a full bin of ice, both in a 72  ̊F 

ambient temperature condition. For cooled-storage ice makers, the “ice storage energy” is the 

energy required to maintain the ice bin temperature below freezing. For uncooled-storage ice 

makers, ice storage energy is the energy required to replace ice that melts. The results of these 

tests are presented in Table 5.19.

Table 5.19 Ice Maker Test Results

Product 

Class

Harvest Rate 

(lb/day)

Icemaking 

Energy 

(kWh/yr)

Ice Storage 

Energy 

(kWh/yr)

Annual Energy 

Consumption 

(kWh/yr)

IM-P 27 125 131 256

IM-P 33 54 35 89

IM-C 10 417 135 552

IM-C 14 312 99 411

IM-U 42 201 875 1,075

IM-U 25 224 448 672
5-37

5.9.2 Efficiency Levels

Because there are no current Federal, State, or industry energy conservation standards for 

ice makers, and because the proposed DOE test procedure is not consistent with any established 

test procedure, there is no established baseline efficiency level for these products. Therefore, 

DOE developed its analysis based on the above energy test results, selecting both baseline and 

maximum-efficiency units for each class based on the data.

DOE analyzed incremental ELs that spanned the range of energy consumption observed 

from all available data, as presented above in Table 5.19. The lowest efficiency that it observed 

in each product class, which DOE called EL 0, was 100 percent of the baseline unit’s energy 

consumption. DOE considered intermediate ELs in 5 percent increments (10-percent increments 

for portable ice makers, which spanned a greater range of efficiency) down to the energy 

consumption of the maximum-efficiency unit in each product class. Although these incremental 

ELs do not represent energy use observed in the tests described above, DOE believes that these 

ELs are possible through partial adoption of the design differences between the baseline and 

maximum-efficiency units in each product class.

DOE did not estimate costs for a maximum-technology level that exceeded the 

maximum-efficiency unit tested for any of its proposed ice maker product classes. DOE observed 

that there would not be sufficient space to increase the size of the heat exchangers of the 

maximum-efficiency tested units. Also, the components (e.g., fans and compressors) used in the 

maximum-efficiency units were generally the highest efficiency available to the manufacturers 

for use in ice makers (e.g., the maximum-efficiency IM-U unit uses a brushless DC condenser 

fan). Finally, DOE concluded that accurate prediction through the use of theoretical energy 

modeling of improved efficiency using other design options would be difficult.

The range of ELs that DOE considered in its ice maker analysis is presented in Table 

5.20, Table 5.21, and Table 5.22.

Table 5.20 Portable Ice Maker Efficiency Levels

Efficiency Level Energy Consumption 

(kWh/year)

Percent of Baseline Energy 

Consumption

EL 0 (Baseline) 256 100%

EL 1 230 90%

EL 2 205 80%

EL 3 179 70%

EL 4 154 60%

EL 5 128 50%

EL 6 102 40%

EL 7 (Max-Available) 89 35%
5-38

Table 5.21 Cooled-Storage Ice Maker Efficiency Levels

Efficiency Level Energy Consumption 

(kWh/year)

Percent of Baseline Energy 

Consumption

EL 0 (Baseline) 552 100%

EL 1 524 95%

EL 2 497 90%

EL 3 469 85%

EL 4 442 80%

EL 5 414 75%

EL 6 (Max-Available) 411 74%

Table 5.22 Uncooled-Storage Ice Maker Efficiency Levels

Efficiency Level Energy Consumption 

(kWh/year)

Percent of Baseline Energy 

Consumption

EL 0 (Baseline) 1,075 100%

EL 1 1,021 95%

EL 2 968 90%

EL 3 914 85%

EL 4 860 80%

EL 5 806 75%

EL 6 753 70%

EL 7 699 65%

EL 8 (Max-Available) 672 63%
5-39

5.9.3 Ice Maker Results

DOE developed cost-efficiency relationships for all three proposed product classes of ice 

makers based on the measured test results and the calculated cost differences between the leastefficient (baseline) and most-efficient (max-available) models that it tested in each class. The 

calculated cost differences focused on design details that DOE considered to influence energy 

use, for example, refrigeration system cost and cabinet construction. In general, DOE developed 

the costs for most of these design options using the same methodology outlined in section 5.2. 

Using the incremental cost for the maximum efficiency design, DOE calculated costs for the 

selected intermediate efficiency levels using interpolation. The incremental MSPs for the three 

ice maker product classes are presented in Table 5.23 through Table 5.25.

Table 5.23 Incremental Manufacturer Selling Price Results for Portable Ice Makers

Efficiency Level (percent of baseline energy use) Total Added MSP

EL 0 (100% -- Baseline) $0

EL 1 (90%) $1.30

EL 2 (80%) $2.59

EL 3 (70%) $3.89

EL 4 (60%) $5.18

EL 5 (50%) $6.48

EL 6 (40%) $7.78

EL 7 (35% -- Max-Available) $8.43

Table 5.24 Incremental Manufacturer Selling Price Results for Cooled-Storage Ice Makers

Efficiency Level (percent of baseline energy use) Total Added MSP

EL 0 (100% -- Baseline) $0

EL 1 (95%) $3

EL 2 (90%) $6

EL 3 (85%) $9

EL 4 (80%) $12

EL 5 (75%) $14

EL 6 (74% -- Max-Available) $16
5-40

Table 5.25 Incremental MSP Results for Uncooled-Storage Ice Makers

Efficiency Level (percent of baseline energy use) Total Added MSP

EL 0 (100% -- Baseline) $0

EL 1 (95%) $3

EL 2 (90%) $7

EL 3 (85%) $10

EL 4 (80%) $14

EL 5 (75%) $17

EL 6 (70%) $21

EL 7 (65%) $23

EL 8 (63%) $26

5.10 HYBRID REFRIGERATION PRODUCTS ANALYSIS AND RESULTS

Hybrid refrigeration products are similar in design, construction, and operation to 

consumer refrigeration products that are already covered and are subject to Federal energy 

conservation standards (i.e., refrigerators, refrigerator-freezers, and freezers) and use identical 

components - the key difference being the inclusion of one or more compartments operated at 

warmer temperatures that comprise at least half of a hybrid product’s refrigerated volume. 

Because hybrid refrigeration products and conventional refrigerators, refrigerator-freezers, and 

freezers are functionally and physically similar, DOE considered whether it would be appropriate 

to apply the 2014 energy conservation standards for conventional refrigeration products to hybrid 

products, using adjustments to account for the different average compartment temperatures of 

hybrid products.

To this end, DOE conducted analysis to evaluate hybrid product energy use and whether 

this energy use would be compliant with an appropriate application of the 2014 energy 

conservation standards. The results of this analysis, presented in this section, indicate that this 

standard can be applied to hybrid products if they use design options that are available and 

commonly used in refrigeration products. 

5.10.1 Comparison of Hybrid and Conventional Refrigeration Products

Hybrid refrigeration products are constructed using the same types of technologies as 

conventional refrigerator-freezers (e.g., polyurethane foamed insulation cabinet construction, 

vapor-compression refrigeration systems, and the same compressor, heat exchanger, and fan

options). The key differences are that (1) at least one of the compartments in a hybrid 

refrigeration product, representing at least half the refrigerated volume, is a cellar compartment, 

not designed to achieve storage temperatures lower than 39  ̊F; (2) the hybrid refrigeration 

product doors that provide access to the cellar compartment(s) are often transparent, constructed 

using glass layers; and (3) the usage profile of a hybrid refrigeration product is expected to more 

closely resemble the usage profile of a cooled cabinet (wine chiller) rather than that of a 
5-41

refrigerator or refrigerator-freezer. These differences are reflected in the proposed test procedure 

for hybrid refrigeration products, which would specify a cellar compartment standardized 

temperature of 55 °F and would apply a usage adjustment factor of 0.85 to calculate energy 

consumption. These differences would affect the measured energy consumption of hybrid 

refrigeration products, as compared to conventional refrigerator-freezers, in the following ways:

1) Thermal load associated with the 50 percent or greater portion of the refrigerated volume that 

is not capable of maintaining compartment temperatures lower than 39  ̊F would be lower 

than the thermal load of a fresh food or freezer compartment. Specifically, the temperature 

difference with respect to ambient for this portion of the volume would be 35  ̊F (90  ̊F minus 

55  ̊F) rather than 51  ̊F (90  ̊F minus 39  ̊F) for a fresh food compartment or 90  ̊F (90  ̊F 

minus 0  ̊F) for a freezer compartment.

2) Thermal load associated with the transparent doors would be greater than the thermal load 

associated with a solid door. For doors that enclose cellar compartments, the additional load 

of the transparent doors would be balanced by the reduced load of the warmer compartment 

temperatures. For transparent doors covering the entire product, including fresh food 

compartments, an approach used in some hybrid refrigerator products, clearly the thermal 

load for a transparent fresh food door would be greater than the load of an identical 

compartment with a solid door.

3) The 0.85 usage adjustment factor would reduce the measured energy use.

The proposed test procedure for hybrid refrigeration products also proposes applying a 

volume adjustment factor of 0.69 to the measured storage volume of cellar compartments. 

Consequently, a hybrid refrigeration product would have a lower maximum allowable energy 

consumption compared to that of a refrigerator, refrigerator-freezer, or freezer of the same 

refrigerated volume. Ultimately this volume adjustment factor and the combined effects of the 

factors listed above would lead to a level of stringency when considering compliance with a 

given standard that may be greater or less than for a conventional refrigeration product.

DOE expects that the refrigeration system efficiency of a hybrid product would be 

equivalent to that of a corresponding conventional refrigeration product. The evaporating 

temperatures and condensing temperatures would be similar. In order to transfer the refrigeration 

capacity to the cabinet, the evaporating temperature would be somewhat lower than the coolest 

compartment temperature, which would be identical for comparable hybrid and conventional 

refrigeration products. For example, for a hybrid refrigeration product having only fresh food 

and cellar compartments, the coolest compartment temperature during the test would be near 39 

 ̊F (generally just above or below this temperature, depending on the control setting). Similarly, 

the coolest compartment temperature for an all-refrigerator without a freezer compartment would 

be near 39  ̊F. The condensing temperatures would be somewhat higher than the test-prescribed

90  ̊F ambient temperature for both types of products. Because the evaporating and condensing 

temperatures of comparable hybrid and conventional refrigeration products’ refrigeration 

systems would be similar, and because the same compressors are available for and can be used in 
5-42

all of these products, the refrigeration system coefficient of performance (COP) would be 

equivalent for these products. This is in contrast to cooled cabinets, for which the coolest 

compartment temperature during testing would be near 55  ̊F, and for which the refrigeration 

system COP could therefore be very different than for conventional refrigerators, whose

standardized compartment temperature is 39  ̊F (e.g., for the fresh food compartments of 

refrigerators).

5.10.2 Analysis Approach

In order to evaluate the suitability of the 2014 energy conservation standard levels for 

hybrid refrigeration products, DOE conducted an analysis to quantify the impacts of the three 

key potential differences in measured energy use for hybrid refrigeration products discussed 

above, as well as the impact of the volume adjustment factor. DOE compared the thermal load of 

various configurations of hybrid refrigeration products to the thermal load of a comparable allrefrigerator and evaluated whether the stringency of the 2014 energy standards would be 

increased or decreased for hybrid refrigeration products as compared with an all-refrigerator.

DOE conducted this analysis using the energy modeling tools described in section 5.5, 

including the ERA energy model and the WINDOW model for calculating the thermal resistance 

of the glass doors. DOE evaluated three hybrid designs with characteristics as follows:

1) One single glass door covering both the cellar compartment and the fresh food 

compartment 

2) Dual glass doors, one for each compartment

3) Dual doors: glass for the cellar compartment and solid for the fresh food compartment

For compact hybrid products, DOE considered all three scenarios, although the first and 

second scenarios are most common in compact hybrid products. For standard-sized hybrid 

products, DOE only considered the second and third scenarios, although the third scenario is 

most common in standard-sized hybrid products. DOE did not consider the first scenario (single 

glass door) for standard-sized products because no such products currently exist on the market. 

To examine the sensitivity of the load to different design details, DOE modeled the products with 

two different insulation thicknesses (1.5 and 2 inches) and three different glass door designs. The 

glass door designs are consistent with those used for the cooled cabinet engineering analysis 

described in section 5.6: a baseline glass door having two uncoated panes with air insulation, a 

medium-tech door having two glass layers, each with low-e coating, and argon insulation, and a

max-tech door design having three glass layers, each with low-e coating, and krypton insulation. 

DOE also modeled hybrid products with both 50-percent and 75-percent cellar volume to 

examine the effects of the volume adjustment factor. DOE performed this analysis for a 6 cubic 

foot product which, as an all-refrigerator, would be of class 13A (compact all-refrigerators with 

automatic defrost) and a 12 cubic foot product corresponding to class 3A (all-refrigerators with 

automatic defrost). Table 5.26 summarizes the product configurations analyzed, and Table 5.27 
5-43

summarizes the design options and combinations of design options considered to improve 

efficiency.

Table 5.26 Hybrid Product Configuration

Size Cellar Volume 

(%)

Doors

Fresh Food Cellar

Compact: 6 ft3

50%

Solid Glass

Glass Glass

Single Glass Door Covering Both Compartments

75%

Solid Glass

Glass Glass

Single Glass Door Covering Both Compartments

Standard: 12 ft3

50% Solid Glass

Glass Glass

75% Solid Glass

Glass Glass

Table 5.27 Design Options Analyzed for Hybrid Products

Descriptions of Individual Design Options

Insulation • Baseline: 1.5-inch Thickness

• 2-inch Thickness

Transparent Doors • Baseline: Two uncoated glass layers, air fill

• Two low-emissivity glass layers, argon fill

• Three low-emissivity glass layers, krypton fill

Compressor Efficiency (compact products)

System COP/EER*

• Baseline: 0.82 / 2.8 Btu/h-W

• 0.94 / 3.2 Btu/h-W

Compressor Efficiency (standard-size 

products)

System COP/EER*

• Baseline: 1.58 / 4.8 Btu/h-W

• 1.91 / 5.8 Btu/h-W

Descriptions of Design Option Combinations

Tech 1 Baseline + 2-inch Insulation

Tech 2 Baseline + 2-inch Insulation + Mid Tech Glass

Tech 3 Baseline + 2-inch Insulation + Mid Tech Glass + Higher Efficiency Compressor

Tech 4 Baseline + 2-inch Insulation + Max Tech Glass

Tech 5 Baseline + 2" Insulation + Max Tech Glass + Higher Efficiency Compressor

*System performance is the net capacity (evaporator capacity minus evaporator fan heat) divided 

by system power input during the compressor on-cycle, including power input of the compressor, 

fans, and control components.
5-44

The candidate system efficiencies can be reasonably achieved by available compressors 

and fan motors. For example, for standard-size systems, an Embraco EMY60HER compressor 

has a nominal capacity of 610 Btu/hr and EER of 5.04 at traditional compressor rating conditions 

of -10  ̊F evaporating temperature and 130  ̊F condensing temperature—this level of performance 

is far from the peak levels achieved by modern compressors. When operating with an 

evaporating temperature of 14  ̊F and a condensing temperature of 113  ̊F in a system cooling a 

refrigerator, using fans that draw 6 W each and a control system that draws 6 W, the system EER 

is 7.0 Btu/h-W.

For the selected product configurations, DOE first calculated the range of expected 

thermal loads for the hybrid product and for the conventional refrigerator. DOE then proceeded 

to compare the energy use of otherwise comparable refrigerators and hybrid refrigeration 

products. The energy use of a conventional refrigerator with one fresh food compartment would 

be as shown in Equation 1, where Lff is the thermal load of the single large fresh food 

compartment, and COP is the unit’s coefficient of performance: 

Equation 1

ERRR = L

CCC

DOE assumed that this refrigerator is minimally compliant with the 2014 standards—

hence ERef is identically equal to the standard for a product of the specified volume of the given 

product class. The value of COP need for compliance with the standards can be determined 

based on the calculated values for ERef and Lff. DOE only considered values of Lff for which the 

calculated COP can be achieved by available refrigeration systems.

The energy use of a hybrid refrigeration product would be as shown in Equation 2, where 

Lh is the thermal load of the hybrid cabinet. As mentioned above, DOE considered several hybrid 

configurations, so Lh has a range of values. The value of COP determined for the all-refrigerator 

is used to convert the term to an expression containing calculated loads and the refrigerator 

energy use.

Equation 2

EHHHHHH = 0.85 ×

Lh

CCC = 0.85 × ERRR ×

Lh

L

DOE conducted this analysis for hybrid product configurations as described in Table 

5.26above, using design option combinations as described in Table 5.27. For each product/design 

option combination, DOE determined the energy use and by what percentage the energy use is 

above or below the standard level, calculated based on product adjusted volume using the 0.69 

volume adjustment factor for the cellar compartment.
5-45

5.10.3 Results

The results of the hybrid product analyses are presented in Table 5.28 as percentages 

representing by what amount the energy use of the analyzed configurations are above or below 

the calculated standard levels. For example, a -19 percent indicates that the product’s energy use 

is 19 percent below the calculated standard level. The analysis shows that all of the analyzed 

product configurations can be designed to be compliant with one of the considered groups of 

design options. Furthermore, the analysis shows that none of the product configurations require 

use of maximum-technology glass doors to achieve compliance, other than the standard-size 

product with 50-percent cellar volume and separate glass doors on both the cellar and fresh food 

compartments. However, as discussed above, this is not considered to be a common product 

configuration, and the use of a solid door on the fresh food compartment would avoid required 

use of maximum-technology glass doors. This analysis shows that the suggested approach for 

application of the 2014 refrigeration product standards to hybrids is achievable for hybrid 

refrigerators using design options that are in currently common use.
5-46

Table 5.28 Hybrid Refrigeration Product Design Changes

Size

Cellar 

Percentage 

Volume

Doors

BaselineTech 1Tech 2Tech 3Tech 4Tech 5

Cellar Fresh 

Food

Compact

50%

Solid Solid -8% -19% - - - -

Glass Solid 16% 4% -7% -20% -12% -24%

Glass Glass 54% 44% 12% -3% -1% -15%

Single Solid Door -17% -29% - - - -

Single Glass Door 45% 25% 3% -11% -10% -23%

75%

Solid Solid -11% -22% - - - -

Glass Solid 26% 15% -3% -17% -11% -24%

Glass Glass 45% 35% 7% -8% -5% -19%

Single Solid Door 21% -32% - - - -

Single Glass Door 36% 26% -3% -16% -15% -27%

Standard

50%

Solid Solid -5% -19% - - - -

Glass Solid 27% 14% -2% -19% -9% -25%

Glass Glass 76% 37% 23% 2% 6% -12%

75%

Solid Solid -10% -22% - - - -

Glass Solid 41% 7% 4% -14% -7% -23%

Glass Glass 66% 55% 17% -3% 0% -17%
5-47

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