became effective in 1993.53 There may be limited additional energy savings possible through 

optimization of automatic defrost. 

Adaptive Defrost 

To reduce the energy used for defrost, adaptive defrost can be used. An adaptive defrost 

system can control both the defrost time and the amount of defrost heat. Adaptive defrost 

systems make use of controls to adjust the time between defrost cycles to the appropriate amount 

for the door opening frequency, ambient conditions, and other consumer usage patterns which 

affect the introduction of moisture into the cabinet. In a typical automatic defrost system, a 

mechanical timer initiates defrost after a specified time period, usually 10 to 12 hours of 

compressor on-time. By allowing adjustment of the time between defrosts, energy use can be 

reduced. The DOE energy test procedure includes modified test procedures for evaluating the 

energy use of products with adaptive defrost. In its 1995 TSD, DOE estimated that energy 

consumption can be reduced by three to four percent with adaptive defrost.53 It is unclear what 

percentage of the refrigerator market currently uses adaptive defrost. 

Condenser Hot Gas 

Another method of reducing the energy required for defrost is to eliminate the need for 

electric heaters by substituting condenser hot gas in their place. In a condenser hot gas defrost 

system, the compressor continues to run and a valve opens allowing hot compressed refrigerant 

to flow to the evaporator. Many frost-free refrigerator-freezers in the 1960s and 1970s used such 

a defrost system. 

3.3.2.11 Control System 

The control systems discussed here pertain to those controlling the temperature and airdistribution within the refrigeration product. 

Temperature Control 

Conventional thermostats are thermomechanical devices that are not very accurate. The 

inaccuracy of these devices may produce large temperature fluctuations within the cabinet and, 

in turn, thermodynamic inefficiencies. Electronic thermostats are available that can provide more 

precise and repeatable temperature control than conventional thermostats. This can result in 

improved efficiency. Electronic thermostat systems can also account for more parameters than 

just the cabinet temperature, such as the room temperature, to better regulate product operation 

and reduce compressor run times. 

Air-Distribution Control 

 For refrigerator-freezers, better air distribution between the freezer and fresh food 

compartments can improve temperature control and reduce energy consumption. Improving the 

distribution of cold air within the refrigerator-freezer allows the temperature difference between 

the air and foodstuffs to be minimized, enabling the evaporation temperature to be raised and, 

thereby, reducing energy consumption. It is uncertain to what degree the air distribution control 

in current refrigerator-freezer models can be improved. However, the fact that several patents 

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have been issued in the U.S. since 1995 regarding air distribution implies that improvements in 

air distribution control are possible.55 

3.3.2.12 Other Technologies 

Alternative refrigerants and changing the location of refrigeration components can also 

improve the efficiency of refrigeration products. These two technology options are discussed 

below. 

Alternative Refrigerants 

Through the 1980s, CFC-12, a chlorofluorocarbon, was used as the refrigerant in almost 

all refrigerators, refrigerator-freezers, and freezers. However, under the Montreal Protocol, all 

CFCs were banned from use by the mid-1990s due to their high ozone depletion potential (ODP). 

In the early 1990s, many alternative refrigerants were evaluated as a replacement for CFC-12. Of 

the alternatives considered, the industry settled on HFC-134a as the replacement for CFC-12. 

Although initial research demonstrated that HFC-134a as a drop-in replacement yielded 

efficiencies which were four to 10 percent less than CFC-12, further work showed that with the 

appropriate superheat and subcooling taken into consideration, HFC-134a could yield essentially 

equivalent system efficiencies as CFC-12.86 

Because HFC-134a exhibits some global warming potential (GWP), research continued 

to find an alternative refrigerant with less or no GWP. For example, R-152a has a lower GWP 

than HFC-134a but, primarily due to flammability concerns and the potential liability issues it 

posed to refrigerator manufacturers, it was dismissed as a potential alternative. 

Naturally occurring substances such as carbon dioxide, ammonia, and hydrocarbons are 

all considered to be environmentally safe refrigerants with very low GWP. Hydrocarbons in 

particular are attractive due to their similar thermodynamic properties to CFC-12. Much research 

has been conducted showing the efficiency benefits of hydrocarbons. For example, the 

performance of propane/isobutane and propane/butane mixtures in domestic refrigerators has 

been shown to be equal to or better than products using CFC-12.87, 88 Hydrocarbon flammability 

has been pointed out as a significant drawback and has prevented their adoption in U.S. products. 

In contrast, European refrigerator manufacturers started manufacturing products with isobutane 

in the 1990s. However, recently the General Electric Company announced the intention to 

introduce this refrigerant in the U.S.89 

Component Location 

In its 1995 TSD, DOE saw energy savings potential in more optimal placement of certain 

components. For example, if the compressor and condenser are located on the top of the 

refrigerator-freezer, DOE determined that they can operate more efficiently because heat is more 

readily convected away from the system and, in addition, the condenser fan can be eliminated. 

As described previously, traditionally, the compressor and condenser are located at the bottom 

rather than the top of the refrigerator-freezer so the user can have easy access to the food 

compartments, to key center of gravity low, and to provide air flow and a heat source near the 

tray which collects defrost water to assure quick re-evaporation of water. Locating the condenser 

and compressor at the top of the unit would require modification of traditional practice and 

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consumer preference. It would also require product redesign, which could potentially increase 

manufacturing costs. 

Another option is to locate the evaporator fan motor outside the cabinet to reduce internal loads 

from the heat loss of the motor. However, it is difficult to prevent air leakage where the motor 

shaft penetrates the cabinet wall. The 1995 TSD concluded that the lack of experimental data 

prevented the evaluation of component relocation.53 

3.3.2.13 Alternative Refrigeration Cycles 

Alternative refrigeration cycles may have the potential to improve system efficiency. 

Several alternative refrigeration cycles for refrigerator-freezers are described below. Dual-loop 

refrigerator-freezers using two independent refrigeration cycles (one for the fresh food 

compartment and the other for the freezer compartment) are available on the market. Also, dualevaporator units likely utilizing a control valve system are also being marketed. The other 

alternatives listed below have been demonstrated in prototypes to reduce energy consumption but 

it is uncertain as to whether they can be mass produced as a practical alternative to today’s 

current conventional refrigeration systems. 

Lorenz-Meutzner Cycle 

In a conventional refrigerator-freezer, the temperature of the freezer and fresh food 

compartments are around 5oF (-15oC) and 38oF (3.3oC), respectively. This suggests that the fresh 

food compartment with a smaller temperature lift (i.e., the temperature difference between the 

evaporator and condenser) can operate with a higher efficiency than that of the freezer. By using 

zeotropicg

 refrigerant mixtures, the Lorenz-Meutzner cycle exploits the inherent thermodynamic 

advantages of the temperature glide exhibited during evaporation or condensation of the 

refrigerant mixture. By choosing a refrigerant mixture with very wide temperature glide, the 

refrigerant mixture can pass sequentially through the freezer and fresh food compartment 

evaporators, providing refrigeration at the two evaporating temperature levels using a single 

compressor. As compared to a conventional refrigerator-freezer, the hardware differences 

include a high-temperature evaporator for the fresh food compartment and a low-temperature 

heat exchanger between the fresh food and freezer evaporators. Lorenz and Meutzner in their 

research determined that their cycle using an R-22/R-11 refrigerant mixture (50 percent of each) 

achieved up to 20 percent energy savings compared to a conventional refrigerator-freezer using 

R-12 only.90 

Subsequent research validated Lorenz and Meutzner’s findings and demonstrated the 

viability of the cycle based on the use of different zeotropic refrigerant mixtures, including 

mixtures composed of hydrocarbons. For example, as compared to a conventional refrigeratorfreezer, experimentation on an 18 ft3 top-mount refrigerator-freezer demonstrated that a modified 

g

 A zeotropic mixture consists of two or more refrigerant components. Zeotropic mixtures have what is referred to as 

a temperature glide when they boil and condense: at a fixed pressure, the temperature is higher for higher quality 

(i.e. vapor fraction). Unlike zeotropes, azeotropic mixtures consist of two or more refrigerant components that 

behave like a single refrigerant, exhibiting no temperature glide. 

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Lorenz-Meutzner cycle yielded 16.6 percent, 14.6 percent, and 16.7 percent energy savings with 

binary mixtures of R-22/R-123, propane/n-pentane, and propane/n-butane, respectively.91 

Because the industry settled on the use of HFC-134a to replace CFC-12, interest in the 

Lorenz-Meutzner cycle as an alternative to conventional refrigeration cycles declined. 

Dual-Loop System 

One of the best methods to reduce the thermodynamic irreversibilities resulting from the 

operation with a single evaporator in a refrigerator-freezer is to employ two separate 

refrigeration cycles. This system, referred to as a dual-loop system, has two completely separate 

refrigeration cycles which provide cooling for the freezer and fresh food compartments 

independently. In practice, the theoretical benefits of such a cycle are not achieved due to the use 

of two compressors that are smaller and less efficient than the original single compressor. Also, 

dual-loop systems are physically larger and would either increase the product’s external 

dimensions or decrease the usable refrigerator volume. 

Research has demonstrated that the energy savings due to a dual-loop system are a 

function of the cabinet load ratio (defined as the ratio of the fresh food to the freezer cabinet 

loads) and the ratio of the freezer and refrigerator cycle efficiencies. Depending on these two 

parameters, a dual-loop system using HFC-134a can reduce energy consumption by up to 30 

percent compared to a conventional refrigerator-freezer.92 

There are numerous products currently on the market that incorporate dual-compressor 

systems, including Bosch’s Integra line of bottom-mount refrigerator-freezers,93 Sun Frost’s 

RF19 model,94 Northland’s 48-inch side-mount refrigerator-freezer,95 Sub-Zero’s built-in line of 

refrigerator-freezers,96 Liebherr refrigerators,97 etc. 

Two-Stage System 

The two-stage system employs one condenser, two evaporators, two compressors, and at 

least one suction-line heat exchanger. The increased efficiency of this system over a 

conventional system is obtained due to a smaller work requirement that results from the lowpressure ratio for each of the two compressors.98 The two-stage system offers the advantage of 

having one fewer component (a condenser) than the dual-loop system, but has many of the same 

disadvantages (e.g., either increased external dimensions or decreased internal volume). 

Control Valve System 

The control valve system has two evaporators, one for the fresh food compartment and 

one for the freezer compartment, but only one compressor and one condenser. Two different 

length capillary tubes and a control valve are installed between the fresh food and freezer 

evaporator inlets and the condenser outlet. The valve directs the flow of the refrigerant through 

one of the evaporators at a time. That is, only one of the two compartments is cooled at any 

given time. With this configuration, the fresh food compartment is cooled at a higher evaporator 

temperature than the freezer compartment. Experimental research conducted on this system 

configuration indicated that the energy efficiency can be improved by 8.5 percent over that of a 

conventional refrigerator-freezer.99 

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GE offers a refrigerator-freezer system called the ClimateKeeper2TM system that uses two 

evaporators.100 Also, KitchenAid and Jenn-Air both offer under-counter compact refrigeratorfreezers that use dual evaporators.101 102 The system details of none of these products is clearly 

described in the product literature. 

Ejector Refrigerator 

One of the intrinsic losses in a conventional refrigeration cycle is the throttling of the 

refrigerant in the capillary tube. Throttling is an isenthalpic process in which work that could be 

extracted in the expansion process is not captured. In the ejector refrigerator, some of this work 

can be captured and used to raise the pressure of refrigerant entering the compressor above that 

of the evaporator. Simulation research has been conducted on an ejector refrigerator that consists 

of one compressor, one condenser, two capillary tubes, two evaporators (one for the fresh food 

compartment and the other for the freezer compartment), and an ejector. In this refrigerator, 

saturated liquid refrigerant exits the condenser and expands in the capillary tube to the fresh food 

evaporator. In the fresh-food compartment, the refrigerant is partially evaporated. At the outlet of 

the evaporator, the liquid refrigerant is separated from the vapor in a separator. The vapor flows 

to the ejector, where it is accelerated to high velocity. The liquid expands in a second capillary 

tube to the freezer evaporator, where it evaporates entirely. The vapor leaving the freezer 

evaporator is entrained in the high-velocity flow of the vapor which left the fresh food 

evaporator. The mixed flow is decelerated to increase its pressure. The mixed flow higher 

pressure flow passes to the compressor suction port to be compressed. This particular ejector 

refrigerator was shown to have an efficiency which is 12.4 percent higher than a conventional 

refrigerator-freezer.103 

Tandem System 

Like the control valve system and the ejector refrigerator, the tandem system uses two 

evaporators (one for the fresh food compartment and another for the freezer compartment), one 

condenser, and one compressor. Refrigerant flows in series first through the fresh food 

evaporator, then the freezer evaporator, and it passes a second time through the fresh food 

evaporator. The warm liquid refrigerant leaves the condenser and flows to fresh food evaporator 

without a first expansion. In the fresh food evaporator the refrigerant liquid undergoes heat 

exchange with the evaporating refrigerant which has passed through the freezer evaporator. The 

temperature of the liquid is reduced by this heat exchange. The liquid then passes through the 

capillary tube where its pressure is reduced. The two-phase refrigerant then passes through the 

freezer evaporator and absorbs heat from the freezer compartment. This vaporization process 

only occurs when the freezer evaporator fan is turned on by the freezer thermostat. The 

refrigerant then passes back through the fresh food evaporator. Here, if the refrigerant has not 

already been vaporized (i.e., the freezer compartment does not require cooling), it vaporizes as a 

result of absorbing heat from the fresh food compartment and the warm liquid. The superheated 

refrigerant then flows to the compressor suction port. At the beginning of the compressor run, the 

fresh-food compartment fan is turned on first. Thus, the fresh food compartment is cooled before 

the system reaches steady state. As a result, the system uses the pull-down period of each cycle, 

which is generally not suitable for cooling the freezer, to cool the fresh food compartment. This 

particular tandem system was shown to reduce energy use by 18 percent compared to a 

conventional refrigerator-freezer.104 

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3.3.2.14 Alternative Refrigeration Systems 

Alternative refrigeration systems do not use vapor compression to provide refrigeration. 

Three alternative refrigeration systems are discussed below: the Stirling cycle, thermoelectric 

cooling, and thermoacoustic cooling. Although research and development has been conducted on 

each of these systems, and thermoelectric compact refrigerators and wine coolers are currently 

being marketed, none are a viable alternative for standard-size refrigerators, refrigerator-freezers, 

and freezers. 

Stirling Cycle 

A Stirling-cycle machine is a device that operates on a closed regenerative 

thermodynamic cycle, with cyclic compression and expansion of the working fluid at different 

temperature levels, and where the flow is controlled by volume changes, so that there is a net 

conversion of heat to work or vice versa. ‘Regenerative’ refers to the use of an internal heat 

exchanger, the regenerator, which is an essential part of the Stirling cycle. A Stirling 

refrigeration cycle compresses and expands an inert gas in a single cylinder. Heat is rejected at 

one end of the cylinder and absorbed at the opposite end. In the absence of all thermodynamic 

losses, the efficiency could be higher than for vapor compression systems, but there are various 

technical difficulties that have so far limited the use of Stirling-cycle cooling to small prototype 

domestic refrigerators. There is no circulating refrigerant fluid and the hot and cold heat areas are 

relatively small, which creates heat exchange challenges for any but the lowest-capacity systems. 

Thermoelectric 

Thermoelectric cooling occurs when a current is passed across the junction of two 

dissimilar metals. One side of the device becomes hot and the other cold. Materials 

(semiconductors) have relatively recently been developed that have allowed for the use of this 

type of cooling in some applications. Thermoelectric cooling devices have no moving parts, do 

not age, and have extremely long lifetimes. There are several compact refrigerators and wine 

coolers using thermoelectric cooling that are being marketed, including several models offered 

by Avanti Products.105 However, they have very low efficiency and are not yet suitable for 

standard-size domestic refrigerator-freezers. 

Thermoacoustic 

Acoustic cooling uses a sound generator inside a closed tube to vibrate a gas and cause 

alternate compression and expansion and therefore heating and cooling. The efficiency of 

prototypes have not been as high as vapor compression systems and the devices have been 

physically large for the amount of cooling produced. 

3.3.3 Energy Efficiency 

DOE gathered data on the energy efficiency of residential refrigerators, refrigeratorfreezers, and freezers currently available in the marketplace. DOE created a database of the 

current models by surveying manufacturers’ websites. The data provide an overview of the 

energy efficiency of each product class covered by this rulemaking. 

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For the models in the DOE database, Figure 3.3.3 through Figure 3.3.22 present by 

product class the relationship between rated annual energy use and adjusted volume. In each 

figure, lines representing the maximum allowable energy consumption (i.e., the current 

minimum efficiency standard) and the current ENERGY STAR level (that took effect in April 

2008 for standard-size refrigerators and refrigerator-freezers), are provided. This allows for a 

quick visual inspection of the number of models that met the ENERGY STAR level. 

The data representing all-refrigerators are highlighted in the figures for product classes 1, 

3, 11, and 13. For product classes 1 and 11, the products which are not all-refrigerators could be 

either basic refrigerators or manual defrost refrigerator-freezers. For product classes 3 and 13, 

the products which are not all-refrigerators are refrigerator-freezers. The percentage of allrefrigerators is high for product class 11 and very high for product class 13. 

The DOE survey found no current models in product class 6, top-mount refrigeratorfreezers with through the door ice and with automatic defrost. DOE still provides a figure for this 

class (Figure 3.3.9) to show the maximum allowable energy consumption for this product class. 

Many of the other product classes also have few products. 

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0 

100 

200 

300 

400 

500 

600 

700 

800 

0 5 10 15 20 25 30 35 40 

Annual Energy Consumption (kWh/yr) 

Federal Minimum Standard 

Energy Star 

Other Refrigerators 

All-Refrigerators 

Adjusted Volume (ft3) 

Figure 3.3.3 Annual Energy Consumption for Refrigerators and Refrigerator-Freezers 

with Manual Defrost (Product Class #1) 

800
 

700
 

Annual Energy Consumption (kWh/yr) 600
 

500
 

400
 

300
 

200
 

100
 

0
 

Federal Minimum Standard 

Energy Star 

0 5 10 15 20 25 30 35
 

Adjusted Volume (ft3) 

Figure 3.3.4 Annual Energy Consumption for Refrigerator-Freezers with Partial 

Automatic Defrost (Product Class #2) 

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Annual Energy Consumption (kWh/yr) 

800 

700 

600 

500 

400 

300 

0 

100 

200 

0 5 10 15 20 25 

Adjusted Volume (ft3) 

30 35 40 

Federal Minimum Standard 

Energy Star 

Refrigerator-Freezers 

All-Refrigerators 

Figure 3.3.5 Annual Energy Consumption for Top-Mount Refrigerator-Freezers with 

Automatic Defrost without TTD Ice Service and All-Refrigerators with Automatic Defrost 

(Product Class #3) 

800 

700 

Annual EnergyConsumption (kWh/yr) 

600 

500 

400 

300 

200 

0 

100 

0 5 10 15 20 25 

Adjusted Volume (ft3) 

30 35 

Federal Minimum Standard 

Energy Star 

40 

Figure 3.3.6 Annual Energy Consumption for Side-Mount Refrigerator-Freezers with 

Automatic Defrost without TTD Ice Service (Product Class #4) 

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0 

100 

200 

300 

400 

500 

600 

700 

800 

Annual Energy Consumption (kWh/yr) 

Federal Minimum Standard 

Energy Star 

0 5 10 15 20 25 30 35 40
 

Adjusted Volume (ft3) 

Figure 3.3.7 Annual Energy Consumption for Bottom-Mount Refrigerator-Freezers with 

Automatic Defrost without TTD Ice Service (Product Class #5) 

800
 

700
 

Annual Energy Consumption (kWh/yr) 600
 

500
 

400
 

300
 

200
 

100
 

0
 

Federal Minimum Standard 

Energy Star 

0 5 10 15 20 25 30 35
 40
 

Adjusted Volume (ft3) 

Figure 3.3.8 Annual Energy Consumption for Bottom-Mount Refrigerator-Freezers with 

Automatic Defrost with TTD Ice Service (Product Class 5A) 

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0 

100 

200 

300 

400 

500 

600 

700 

800 

Annual Energy Consumption (kWh/yr) 

Federal Minimum Standard 

Energy Star 

No current products within this class

could be found.

0 5 10 15 20 25 30 35 

Adjusted Volume (ft3) 

Figure 3.3.9 Annual Energy Consumption for Top-Mount Refrigerator-Freezers with 

Automatic Defrost with TTD Ice Service (Product Class #6) 

800 

700 

Annual Energy Consumption (kWh/yr) 600 

500 

400 

300 

200 

100 

0 

Federal Minimum Standard 

Energy Star 

0 5 10 15 20 25 30 35 

Adjusted Volume ft3) 

Figure 3.3.10 Annual Energy Consumption for Side-Mount Refrigerator-Freezers with 

Automatic Defrost with Through-the-Door Ice Service (Product Class #7) 

3-75 

40 

40 

EERE-2008-BT-STD-0012 COMMENT 20
0 

100 

200 

300 

400 

500 

600 

700 

800 

900 

0 5 10 15 20 25 30 35 40 45 

Annual Energy Consumption (kWh/yr) 

Federal Minimum Standard 

Energy Star 

Adjusted Volume (ft3) 

Figure 3.3.11 Annual Energy Consumption for Upright Freezers with Manual Defrost 

(Product Class #8) 

900
 

800
 

Annual Energy Consumption (kWh/yr) 

700 

600 

500 

400 

300 

200 

100 

0 

Federal Minimum Standard 

Energy Star 

0 5 10 15 20 25 30 35 40 45 

Adjusted Volume (ft3) 

Figure 3.3.12 Annual Energy Consumption for Upright Freezers with Automatic Defrost 

(Product Class #9) 

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0 

100 

200 

300 

400 

500 

600 

700 

800 

900 

Annual Energy Consumption (kWh/yr) 

Federal Minimum Standard 

Energy Star 

0 5 10 15 20 25 30 35 40 45 

Adjusted Volume (ft3) 

Figure 3.3.13 Annual Energy Consumption for Chest Freezers and all other Freezers 

except Compact Freezers (Product Class #10) 

900 

800 

Annual Energy Consumption (kWh/yr) 700 

600 

500 

400 

300 

200 

100 

0 

Federal Minimum Standard 

Energy Star 

0 5 10 15 20 25 30 35 40 45 

Adjusted Volume (ft3) 

Figure 3.3.14 Annual Energy Consumption for Chest Freezers with Automatic Defrost 

(Product Class #10A) 

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0 

100 

200 

300 

400 

500 

600 

Annual Energy Consumption (kWh/yr) 

Federal Minimum Standard 

Energy Star 

All-Refrigerators 

Other Refrigerators 

0 2 4 6 8 10 12 14 

Adjusted Volume (ft3) 

Figure 3.3.15 Annual Energy Consumption for Compact Refrigerators and RefrigeratorFreezers with Manual Defrost (Product Class #11) 

600 

Annual Energy Consumption (kWh/yr) 500 

400 

300 

200 

100 

0 

Federal Minimum Standard 

Energy Star 

0 2 4 6 8 10 12 14 

Adjusted Volume (ft3) 

Figure 3.3.16 Annual Energy Consumption for Compact Refrigerator-Freezers with 

Partial Automatic Defrost (Product Class #12) 

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0 

100 

200 

300 

400 

500 

600 

Annual Energy Consumption (kWh/yr) 

Federal Minimum Standard 

Energy Star 

All-Refrigerators 

Refrigerator-Freezers 

0 2 4 6 8 10 12 14 

Adjusted Volume (ft3) 

Figure 3.3.17 Annual Energy Consumption for Compact Top-Mount Refrigerator-Freezers 

with Automatic Defrost and All-Refrigerators with Automatic Defrost (Product Class #13) 

0 

100 

200 

300 

400 

500 

600 

Annual Energy Consumption (kWh/yr) 

Federal Minimum Standard 

Energy Star 

0 2 4 6 8 10 12 14 

Adjusted Volume (ft3) 

Figure 3.3.18 Annual Energy Consumption for Compact Side-Mount Refrigerator-Freezers 

with Automatic Defrost (Product Class #14) 

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0 

100 

200 

300 

400 

500 

600 

Annual Energy Consumption (kWh/yr) 

Federal Minimum Standard 

Energy Star 

0 2 4 6 8 10 12 14 

Adjusted Volume (ft3) 

Figure 3.3.19 Annual Energy Consumption for Compact Bottom-Mount RefrigeratorFreezers with Automatic Defrost (Product Class #15) 

600 

500 

Annual Energy Consumption (kWh/yr) 400 

300 

200 

100 

0 

Federal Minimum Standard 

Energy Star 

0 2 4 6 8 10 12 14 

Adjusted Volume (ft3) 

Figure 3.3.20 Annual Energy Consumption for Compact Upright Freezers with Manual 

Defrost (Product Class #16) 

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0 

100 

200 

300 

400 

500 

600 

Annual Energy Consumption (kWh/yr) 

Federal Minimum Standard 

Energy Star 

0 2 4 6 8 10 12 14 

Adjusted Volume (ft3) 

Figure 3.3.21 Annual Energy Consumption for Compact Upright Freezers with Automatic 

Defrost (Product Class #17) 

600 

500 

Annual Energy Consumption (kWh/yr) 400 

300 

200 

100 

0 

Federal Minimum Standard 

Energy Star 

0 2 4 6 8 10 12 14 

Adjusted Volume (ft3) 

Figure 3.3.22 Annual Energy Consumption for Compact Chest Freezers (Product Class 

#18) 

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REFERENCES 

1	 Title 10—Energy, Chapter II—Department of Energy, Part 430—Energy Conservation 

Program for Consumer Products, Subpart A—General Provisions, Section 430.2— 

Definitions. 

2	 Energy Conservation Program for Consumer Products: Amendment to the Definition of 

“Electric Refrigerator,” Final Rule, November 19, 2001. 66 FR 57845. 

3	 Title 10—Energy, Chapter II—Department of Energy, Part 430—Energy Conservation 

Program for Consumer Products, Subpart A—General Provisions, Section 430.32—Energy 

and Water Conservation Standards and Effective Dates. 

4	 Haier America Trading, LLC. Convertible Bottom Drawer Refrigerator, Model 

PRCS25EDAS. <http://www.haieramerica.com/en/product/PRCS25EDAS> (Accessed 

September 26, 2007.) 

5	 Energy Star. Find Energy Star Qualified Refrigerator & Freezers. 

<http://www.energystar.gov/index.cfm?fuseaction=refrig.search_refrigerators> (Accessed 

September 26, 2007.) 

6	 Energy Conservation Program for Consumer Products: Decision and Order Granting a 

Waiver to the General Electric Company From the Department of Energy Residential 

Refrigerator and Refrigerator-Freezer Test Procedure, Notice of decision and order, 

February 27, 2008. 73 FR 10425. 

7	 Energy Conservation Program for Consumer Products: Decision and Order Granting a 

Waiver to Whirlpool Corporation From the Department of Energy Residential Refrigerator 

and Refrigerator-Freezer Test Procedure, May 5, 2009. 74 FR 20695. 

8	 Energy Conservation Program for Consumer Products: Decision and Order Granting a 

Waiver to Liebherr Hausgeräte From the Department of Energy Electric Refrigerator and 

Electric Refrigerator-Freezer Test Procedures, Notice of decision and order, April, 24, 2007. 

72 FR 20333. 

9	 Yashar, D.A. Repeatability of Energy Consumption Test Results for Compact Refrigerators, 

September 2000. U.S. Department of Commerce, National Institute of Standards and 

Technology, Gaithersburg, MD. NISTIR 6560. 

<http://www.fire.nist.gov/bfrlpubs/build00/PDF/b00055.pdf> 

10	 Association of Home Appliance Manufacturers. Energy, Performance and Capacity of 

Household Refrigerators, Refrigerator-Freezers and Freezers, ANSI/AHAM HRF-1-2008. 

Washington, DC. 

11	 U.S. Environmental Protection Agency. Energy Star Program Requirements for Residential 

Refrigerators and/or Freezers, August 3, 2007. Washington, DC. 

<http://www.energystar.gov/ia/partners/product_specs/program_reqs/refrig_prog_req.pdf > 

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12	 Kosa et al., Consumer Home Refrigeration Practices: Findings from a Consumer Survey, 

presented at the American Dietetic Association Food and Nutrition Conference and Expo, 

Honolulu, Hawaii, September 16–19, 2006. 

13	 Godwin et al., “A Comprehensive Evaluation of Temperatures within Home Refrigerators,” 

Food Protection Trends (March 2007). 

14	 “The Share-of-Market Picture,” Appliance Magazine, September 1993–2006. Vols. 51–63, 

No. 9. 

15	 Maytag. “Whirlpool Corporation and Maytag Corporation Sign Definitive Merger 

Agreement,” Maytag Press Release, August 22, 2005. 

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2007.) 

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59	 “Electrolux's New Vacuum Insulated Freezer Technology,” Appliance Magazine, August 

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63	 U.S. Environmental Protection Agency. Finite Element Analysis of Heat Transfer Through 

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64	 Title 10—Energy, Chapter II—Department of Energy, Part 430—Energy Conservation 

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68	 Woodall, R.J. and Bullard, C.W. “Simulating Effects of Mutispeed Compressors on 

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69	 Embraco. Embraco VCC® 3rd Generation, The Intelligent Compressor, Version 00, 

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September 26, 2007.) 

70	 James, Stephen J. "Developments in domestic refrigeration and consumer attitudes," Food 

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Bristol, UK. Bulletin of the IIR - No 2003-5. <http://www.iifiir.org/en/doc/1051.pdf> 

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71	 Unger, R. “Development and Testing of a Linear Compressor Sized for the European 

Market,” Proceedings of the International Appliance Technology Conference, May, 1999. 

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72	 LG Electronics. "Green Technology Linear DIOS," 2004. 

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73	 LG Electronics. LG Linear Compressor Models. 

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74	 American Council for an Energy-Efficient Economy. "One kWh/day Refrigerator," Emerging 

Technologies & Practices, 2004. Washington, DC. 

75	 Bansal, P.K., Wich, T., Browne, M.W., and Chen, J. “Design and Modeling of New EggCrate-Type Forced Flow Evaporators in Domestic Refrigerators,” ASHRAE Transactions, 

2001, Vol. 107, Pt. 2. 

76	 Bansal, P.K. and van Neuren, O.S. “An Experimental Study on New Egg-Crate Type 

Evaporators in Domestic Refrigerators,” ASHRAE Transactions, 1998, Vol. 104, Pt. 2. 

77	 Goslovich, K.S. and Bullard, C.W. “Potential for Using Enhanced Aluminum Extrusions for 

Refrigerator Heat Exchangers,” ASHRAE Transactions, 1997, Vol. 103, Pt. 1. 

78	 Vineyard, E.A., Horvay, J.B., and Schulak, E.R. “Experimental and Analytical Evaluation of 

a Ground-Coupled Refrigerator-Freezer,” ASHRAE Transactions, 1998, Vol. 104, Pt. 2. 

79	 Bansal, P.K. and Chin, T.C. “Modeling and optimisation of wire-and-tube condenser,” 

International Journal of Refrigeration, 2003, 26 (2003), 601-613. 

80	 Bansal, P.K. and Chin, T.C. “Design and modeling of hot-wall condensers in domestic 

refrigerators,” Applied Thermal Engineering, 2002, 22 (2002), 1601-1617. 

81	 Rebora, A. and Tagliafico, L.A. “Thermal performance analysis for hot-wall condenser and 

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82	 Belko, John. Novel Fan Design Offers Energy Savings to Refrigeration Market, 2007. A.O. 

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83	 Bansal, P.K. and Rupasinghe, A.S. “An Homogenous Model for Adiabatic Capillary Tubes,” 

Applied Thermal Engineering, 1998, Vol. 18, Nos. 3-4, 207-219. 

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84	 Bansal, P.K. and Rupasinghe, A.S. “An empirical model for sizing capillary tubes,” 

International Journal of Refrigeration, 1996, Vol. 19, No. 8, 497-505. 

85	 Coulter, W.H. and Bullard, C.W. “ An Experimental Analysis of Cycling Losses in Domestic 

Refrigerator-Freezers,” ASHRAE Transactions, 1997. Vol. 103, Pt. 1. 

86	 Behrens, N., Dekleva, T.W., Hartley, J.G., Murphy, F.T., and Powell, R.L. “The R-134a 

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1990, pp. 365-372. 

87	 Jung, D., Kim, C-B., Song, K., and Park, B. “Testing of propane/isobutane mixture in 

domestic refrigerators,” International Journal of Refrigeration, 2000, 23 (2000) 517-527. 

88	 Alsaad, M.A. and Hammad, M.A. “The application of propane/butane mixture for domestic 

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89	 Gatta, A., “GE Opening a Door to a Future of Cleaner Home Refrigeration”, GE Press 

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SearchCategoryID= 

90	 Lorenz, A. and Meutzner, K. “On application of non-azeotropic two component refrigerants 

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91	 Liu, Z., Haider, I., and Radermacher, R. “Simulation and Test Results of Hydrocarbon 

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92	 Gan, A.I., Klein, S.A, and Reindl, D.T. “Analysis of Refrigerator/Freezer Appliances Having 

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93	 Bosch. Refrigeration, Integra Bottom-Freezers. <http://www.boschappliances.com/kitchenappliances-refrigerator-freezer_refrigerators_integra_integra-bottom-freezers.html> 

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94	 Sun Frost. The Sun Frost RF19. <http://www.sunfrost.com/refrigerator_models.html> 

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with Stainless Steel Interior/Exterior with Full Length Glass Door. 

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(Accessed September 26, 2007.) 

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96	 Sub-Zero Freezer Company, Inc. Design Guide, Built-In, Integrated, Wine Storage, 

Undercounter. <http://www.subzero.com/resources/products/downloads/szdesignguide.pdf> 

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97	 Liebherr Dual Refrigeration System, http://www.liebherrappliances.com/quick_links/features/dual_refrigeration.html 

98	 Radermacher, R. and Kim, K. “Domestic Refrigerators: recent developments,” International 

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99	 Lavanis, M., Haider, I., and Radermacher, R. “Experimental Investigation of an Alternating 

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100 General Electric Company. GE Consumer & Industrial, Press Room, Refrigerators, GE 

Profile Refrigerators with ClimateKeeper2TM Technology Offer Fresh Solutions in a Variety 

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101 AJ Madison Inc. KitchenAid 27” Double Drawer Refrigerator with 5.3 cu.ft. Capacity, Dual 

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102 US-Appliance. Jenn-Air 27” Built In Under Counter Drawer Refrigerator Stainless Steel. 

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103 Tomasek, M-L. and Radamacher, R. “Analysis of a Domestic Refrigerator Cycle with an 

Ejector,” ASHRAE Transactions, 1995, Vol. 101, Pt. 1. 

104 Kim, K., Kopko, B. and Radamacher, R. “Application of Tandem System to High-Efficiency 

Refrigerator/Freezer,” ASHRAE Transactions, 1995, Vol. 101, Pt. 2. 

105 Avanti Products. <http://www.avantiproducts.com/> (Accessed September 26, 2007.) 

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CHAPTER 4: SCREENING ANALYSIS 

TABLE OF CONTENTS 

4.1 INTRODUCTION ...............................................................................................................4-1 

4.2 SCREENED-OUT TECHNOLGIES............................................................................... 4-2 

4.2.1 Improved Resistivity of Insulation....................................................................... 4-2 

4.2.2 Gas-Filled Panels ................................................................................................. 4-2 

4.2.3 Improved Gaskets, Double Gaskets, Improved Door Face Frame ...................... 4-3 

4.2.4 Reduced Heat Load for TTD Feature .................................................................. 4-3 

4.2.5 Warm Liquid or Hot Gas Refrigerant Anti-Sweat Heating ................................. 4-4 

4.2.6 Electric Anti-Sweat Heater Sizing.......................................................................4-4 

4.2.7 Linear Compressors ............................................................................................. 4-4 

4.2.8 Improved Evaporator Heat Exchange.................................................................. 4-5 

4.2.9 Improved Condenser Heat Exchange................................................................... 4-5 

4.2.10 Fan Blade Improvements ..................................................................................... 4-6 

4.2.11 Improved Expansion Valve.................................................................................. 4-6 

4.2.12 Off-Cycle Valve................................................................................................... 4-7 

4.2.13 Reduced Energy for Automatic Defrost .............................................................. 4-7 

4.2.14 Condenser Hot Gas Defrost ................................................................................. 4-7 

4.2.15 Electronic Temperature Control .......................................................................... 4-8 

4.2.16 Air-Distribution Control ...................................................................................... 4-8 

4.2.17 Alternative Refrigerants....................................................................................... 4-8 

4.2.18 Component Location............................................................................................ 4-9 

4.2.19 Lorenz-Meutzner Cycle ....................................................................................... 4-9 

4.2.20 Dual-Loop System ............................................................................................... 4-9 

4.2.21 Two-Stage System ............................................................................................. 4-10 

4.2.22 Control Valve System and Tandem System ...................................................... 4-10 

4.2.23 Ejector Refrigerator ........................................................................................... 4-10 

4.2.24 Stirling Cycle ..................................................................................................... 4-10 

4.2.25 Thermoelectric ................................................................................................... 4-11 

4.2.26 Thermoacoustic.................................................................................................. 4-11 

4.3 REMAINING TECHNOLOGIES ................................................................................. 4-12 

LIST OF TABLES 

Table 4.2.1 LG Linear Compressor Performance Data ............................................................... 4-4 

LIST OF FIGURES 

Figure 4.2.1 Comparison of Stirling and Vapor Compression Technologies............................ 4-11 

4-i 

EERE-2008-BT-STD-0012 COMMENT 20
CHAPTER 4. SCREENING ANALYSIS 

4.1 INTRODUCTION 

This chapter details the screening analysis that the U.S. Department of Energy (DOE) 

conducted in support of the ongoing energy conservation standards rulemakings for refrigerators, 

refrigerator-freezers, and freezers. 

In chapter 3, the market and technology assessment (MTA), DOE presented an initial list 

of technologies that can improve the energy efficiency of residential refrigeration products. The 

purpose of the screening analysis is to evaluate the technologies that improve equipment 

efficiency to determine which technologies to consider further and which to screen out. DOE 

consulted with a range of parties, including industry, technical experts, and others to develop a 

list of technologies for consideration. DOE evaluated the technologies pursuant to the criteria set 

out in the Energy Policy and Conservation Act (EPCA), as amended. (42 U.S.C. 6311-6317) 

Section 325(o) EPCA establishes criteria for prescribing new or amended standards 

designed to achieve the maximum improvement in energy efficiency. Further, EPCA directs the 

Secretary of Energy to determine whether a standard is technologically feasible and 

economically justified. (42 U.S.C. 6295(o)(2)(A), as directed by 42 U.S.C. 6316(a)(1)-(3)). 

EPCA also establishes guidelines for determining whether a standard is economically justified. 

(42 U.S.C. 6295(o)(2)(B)) Appendix A to subpart C of Title 10, Code of Federal Regulations, 

Part 430 (10 CFR Part 430), “Procedures, Interpretations and Policies for Consideration of New 

or Revised Energy Conservation Standards for Consumer Products” (the Process Rule), sets forth 

procedures to guide DOE in its consideration and promulgation of new or revised equipment 

energy conservation standards. These procedures elaborate on the statutory criteria provided in 

42 U.S.C. 6295(o) and, in part, eliminate problematic technologies early in the process of 

prescribing or amending an energy efficiency standard. In particular sections 4(b)(4) and 5(b) of 

the Process Rule guide DOE in determining whether to eliminate from consideration any 

technology that presents unacceptable problems with respect to the following criteria: 

Technological feasibility. Technologies incorporated in commercial equipment or in 

working prototypes will be considered technologically feasible. 

Practicability to manufacture, install, and service. If mass production of a technology 

in commercial equipment and reliable installation and servicing of the technology could be 

achieved on the scale necessary to serve the relevant market at the time of the effective date of 

the standard, then that technology will be considered practicable to manufacture, install, and 

service. 

Impacts on equipment utility or equipment availability. If a technology is determined 

to have significant adverse impact on the utility of the equipment to significant subgroups of 

customers, or result in the unavailability of any covered equipment type with performance 

characteristics (including reliability), features, sizes, capacities, and volumes that are 

substantially the same as equipment generally available in the United States at the time, it will 

not be considered further. 

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EERE-2008-BT-STD-0012 COMMENT 20
Adverse impacts on health or safety. If it is determined that a technology will have 

significant adverse impacts on health or safety, it will not be considered further. 

In sum, if DOE determines that a technology, or a combination of technologies, has 

unacceptable impacts on the policies stated in section 5(b) of the Process Rule, it will be 

eliminated from consideration. If a particular technology fails to meet one or more of the four 

criteria, it will be screened out. Section 4.2 documents the reasons for eliminating any 

technology. 

4.2 SCREENED-OUT TECHNOLGIES 

This section describes the technologies that DOE eliminated for failure to meet one of the 

following four factors: (1) technological feasibility; (2) practicability to manufacture, install, and 

service; (3) impacts on equipment utility or equipment availability; and (4) adverse impacts on 

health or safety. 

4.2.1 Improved Resistivity of Insulation 

Past research has demonstrated that the resistivity of polyurethane (PU) foam insulation 

can be improved through the use of additives that reduce the thermal conductivity of the foam. 

Research conducted in 1996 demonstrated that adding carbon black provides a means of 

improving the thermal insulation properties of PU foam using both HCFC-141b or cyclopentane 

blowing agents.1

 However, DOE is not aware that this process has been adopted by any supplier 

of PU foam insulation or any refrigerator manufacturer. Manufacturers have reported that it 

darkens the interior of a refrigerator lined with white plastic, and it stains anything it contacts. 

Discussion with PU foam insulation vendors indicates that there is work ongoing which 

may lead to improvement in insulation performance but that any such technology would not 

likely be ready for introduction to the market by 2014. Discussion with manufacturers has 

confirmed that there are no available options for improvement in PU foam insulation 

performance (other than reverting to use of banned blowing agents). Due to the lack of available 

information and predictions that there is no significant benefit to be expected from PU foam 

improvements, DOE has eliminated this option from consideration in the engineering analysis. 

4.2.2 Gas-Filled Panels 

Investigation of the status of gas-filled panels suggests that there has been some 

evaluation of this technology by manufacturers of residential refrigeration equipment, but that no 

manufacturers are using it in their products. The costs are reported to be as high as for vacuum 

insulation panels (VIPs), with less reduction in thermal load. DOE has not been able to identify a 

credible supplier that would provide gas filled panel products to the refrigeration industry. DOE 

has eliminated this technology from further consideration. 

4-2 

EERE-2008-BT-STD-0012 COMMENT 20
4.2.3 Improved Gaskets, Double Gaskets, Improved Door Face Frame 

Past investigation on reduction of heat load in the gasket and door face frame area has 

focused on (1) limiting the conduction of heat through metal casing material passing underneath 

the gasket magnet on the cabinet side or in the region of the gasket clip on the door side into the 

cabinet interior, (2) using a gasket which provides additional cover of frame surfaces towards the 

interior of the magnet to prevent cold air from reaching the high-conductivity metal casing near 

the gasket magnet, and (3) providing a long thin “throat” area between the gasket and the interior 

to limit convection heat transfer. Most current designs are effective in addressing these issues. 

Limited information is publicly available which would allow quantification of additional 

improvement potential for the door frame/gasket area of refrigerators. Some manufacturers use 

extra-strong gasket magnets to limit infiltration and thermal loss, but it is unclear whether 

significant thermal improvement is possible with such systems. Manufacturers indicated during 

pre-NOPR discussions that properly designed and installed gasket systems provide a tight seal 

and that there isn’t any further reduction in air leakage that could be achieved with 

improvements in the gasket system such as increasing the magnetic force. In addition, consumer 

safety laws preclude use of excessive door sealing force. 

Based on information drawn from DOE’s 1995 TSD, double door gaskets were not 

adopted by many manufacturers in the mid-1990s because of performance problems and cost. Ice 

has a tendency to form between the gaskets, greatly reducing their effectiveness. In addition, the 

gaskets tend to be visually unattractive and they make it more difficult to meet the consumer 

safety regulations for minimum door-opening force. 

It is expected that incremental improvement may be possible for some products, however, 

the lack of good quantified information on general improvement potential in this area makes this 

technology option unsuitable for consideration as a design option. 

4.2.4 Reduced Heat Load for TTD Feature 

During Pre-NOPR analysis discussions, manufacturers indicated that there is little or no 

reduction in load which can be achieved through redesign of TTD features. DOE inspected the 

TTD system of a side-by-side refrigerator and concluded that the load impact of this feature is 

modest. The door insulation thickness is maintained behind the recess except within an inch or 

two of the chute opening, and low-conductivity plastic is used on all surfaces. The chute door 

closes reliably. A calculation of the thermal load suggests that it is on the order of 3W (10 

Btu/hr). The reverse engineering of this feature shows that a 2W electric anti-sweat heater is used 

to prevent condensation of the exterior surfaces nearest the ice chute opening. Manufacturers 

indicated that these load levels are typical for TTD features. Even if the chute door was insulated 

with 1⁄2-inch of insulation (which would likely interfere with chute door operation), the load 

impact would be minimal, due to the very low surface area of this door. Based on the very low 

potential for improvement, DOE has eliminated reduced heat load TTD features as an option for 

further analysis. 

4-3 

EERE-2008-BT-STD-0012 COMMENT 20
4.2.5 Warm Liquid or Hot Gas Refrigerant Anti-Sweat Heating 

Although some refrigerators do still use electric anti-sweat heating, the typical anti-sweat 

heater for baseline units, according to the reverse engineering work and discussion with 

manufacturers, is warm liquid refrigerant. A possible exception is French door refrigerators. In 

these products, providing heat to the gasket surfaces which seal between the French doors (or to 

the flip-mullion used in some designs for sealing in this region) is not possible using warm 

refrigerant liquid or hot gas. French door refrigerators may use electric anti-sweat heaters in this 

region, but for these products conversion to refrigerant line anti-sweat is impractical. Due to the 

current use of refrigerant-line anti-sweat in situations where it can be used, DOE has eliminated 

this option from further consideration. 

4.2.6 Electric Anti-Sweat Heater Sizing 

Because the baseline products considered in the engineering analysis predominantly use 

warm liquid anti-sweat, the consideration of adjustment of the sizing of electric anti-sweat 

heaters is not relevant. 

4.2.7 Linear Compressors 

While promising potential has been reported for linear compressors, there is very little 

information available for commercialized linear compressors that allows confident prediction of 

performance and cost impacts of this technology. Information for some LG linear compressors 

has been reported at “LG Reference Conditions,” which are significantly different than the 

standard ASHRAE rating conditions. Under ASHRAE conditions, compressors are rated at -10 

oF (-23.3 oC) evaporating temperature and 130 oF (54.4 oC) condensing temperature. The “LG 

Reference Conditions” are based on -14.8 oF (-26 oC) evaporating and 100.4 oF (38 oC) 

condensing temperatures. It is not clear what the liquid and suction vapor temperatures for the 

LG conditions are—these temperatures also impact capacity and power input. The performance 

of some of LG’s linear compressors at the LG conditions is presented in Table 4.2.1 below. At 

the same evaporating and condensing temperatures and with liquid and suction vapor conditions 

consistent with the ASHRAE test conditions, a high efficiency rotating-shaft reciprocating 

compressor such as the Embraco EGX70HLC would have an operating EER of about 6.9 Btu/hrW. Hence, the LG linear compressor may be about 9% more efficient than the best currenttechnology rotating-shaft reciprocating compressors. 

Table 4.2.1 LG Linear Compressor Performance Data 

Model 

Capacity Range* Efficiency* 

W Btu/hr COP EER 

DLF81LACT 310 1058 2.14 7.3 

FA81LACT 293 1000 2.20 7.5 

FA72LACT 276 941 2.20 7.5 

FA63LACT 241 823 2.20 7.5 

FA54LACT 207 706 2.20 7.5 

Source: LG, 2007. 

* Performance based on ‘LG Reference’ rating conditions. Models utilize refrigerant R134a. 

4-4 

EERE-2008-BT-STD-0012 COMMENT 20
In the trade press, LG has expressed willingness to license the linear compressor 

technology to competitors.2

 However, because the LG design is proprietary, the widespread use 

of linear compressors is highly uncertain. Use of linear compressors in LG refrigerators is less 

explicit in LG product data than it was a few years ago, so it is unclear how many products are 

actually using these compressors. Other compressor manufacturers who have indicated that they 

have investigated linear technology have stated that linear compressor technology does not 

provide a clear path to improved efficiency, and some have indicated that they are no longer 

actively pursuing this technology. Hence, availability of linear compressor technology as an 

option for improved efficiency is uncertain. Further, DOE was not able to obtain cost estimates 

for linear compressors. For these reasons, DOE has eliminated linear compressors from further 

consideration in the analyses. 

4.2.8 Improved Evaporator Heat Exchange 

Improving heat exchanger performance can be achieved through the use of enhanced fins 

and/or tubes. These types of fin and tube enhancements are common in air-conditioning 

applications where slit and louvered designs are used to enhance the fin surface and different 

types of internally-grooved surfaces are used to enhance the tubing. Application of similar 

enhancements in refrigerator evaporators is complicated by frost accumulation on the 

evaporators. Effectiveness of the fine slit and louver features for refrigerator evaporators is 

dubious because they would be blocked quickly with frost. In order to avoid the energy use 

associated with frequent defrost, fin spacing in refrigerator evaporators is comparatively sparse. 

This allows the evaporator to work effectively without blocking airflow with a considerable 

accumulation of frost. During defrost, the typical flat fin design of these evaporators assures that 

the frost slides rapidly off the fins and doesn’t get stuck on fin enhancement features. During 

discussions with manufacturers, little indication was provided that efficiency could significantly 

be enhanced through the use of fin or tube enhancements. DOE has eliminated this option from 

consideration in subsequent analysis. 

4.2.9 Improved Condenser Heat Exchange 

Use of heat exchanger enhancements for the condenser are complicated by the need for 

adequate performance when the heat exchanger has not been cleaned. Most refrigerator 

condensers (other than hot wall condensers integrated into the outer shells of the products) are 

made of steel tubes and steel wire fins. These condensers have a very open construction which 

allows dust to flow through easily and which reduces blockage of air flow if dust does collect on 

the condenser surfaces. Flat fin condensers used in refrigerators are known to require more 

careful attention to cleaning. Use of high fin densities is more accepted in air-conditioning 

applications because periodic maintenance is expected and because size would get enormous if 

aggressive fin spacing wasn’t employed, whereas cleaning of refrigerator condensers occurs 

infrequently or never, and the loads are small enough so that maximizing use of space is not 

critical. DOE has eliminated this option from consideration in subsequent analysis. 

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EERE-2008-BT-STD-0012 COMMENT 20
4.2.10 Fan Blade Improvements 

Refrigerator fan blades use an axial design. They are typically injection molded plastic 

with a three-dimensional shape for improved performance as compared with older stamped sheet 

metal designs. One source of inefficiency for axial fans lies in their tendency to throw air 

outward, necessitating a shroud to collect and redirect airflow along the axis as intended. The 

Pax GroupTM has developed a fan (PAX fan) that employs streamlined blades with patented 

geometrical shapes derived from a naturalistic design approach, providing better airflow 

direction and improved efficiency. Tests performed when replacing existing motor combinations 

with A.O.Smith motors and PAX fan blades show power input reductions in the range of roughly 

10% to 35%.3 It is impossible to tell how much of this benefit is associated with the fan blade 

and how much with the motor. Also, because the PAX fan is proprietary, the widespread use of 

the design is highly uncertain. There is in general little data available to quantify the energy 

benefit possible with improvement in fan blade design in today’s refrigeration products. Fan 

performance is highly dependent on details of integration with the system: orifice geometry, 

tolerance of blade/orifice gap, match of system flow impedence to fan performance, etc. Hence, 

making credible estimates of energy savings potential through fan blade replacement requires 

testing fan blade swaps in baseline products. The cost of fabrication of improved fan blade 

geometries should be low, so most of the cost increase associated with this technology option 

would be associated with paying for the blade development and/or licensing fees. It is very 

difficult to predict what these costs would be unless specific vendors of high efficiency fan 

blades can be identified who provide complete information. During discussions with 

manufacturers, no information was provided which would allow credible calculation of savings 

and costs associated with improved fan blades. Hence, DOE has eliminated this option from 

further consideration. 

4.2.11 Improved Expansion Valve 

Residential refrigeration products exclusively use capillary tubes for refrigerant flow 

metering. These tubes are inexpensive and they lend themselves easily to low-cost fabrication of 

suction line heat exchangers by brazing the capillary to the suction line. Automatic, adjustable 

thermostatic or electronic expansion valves are available, but they generally are oversized for 

residential refrigeration. Furthermore, it is unclear whether there is any potential for energy 

savings using alternative expansion devices. The DOE Energy test is conducted with a single set 

of standardized temperatures for the ambient air (90 °F) and for the compartments. A capillary 

tube can be designed to provide optimized performance for this set of temperatures. Systems are 

generally designed to operate with evaporator exit conditions having little or no superheat during 

energy testing, thus maximizing use of the evaporator. In the lower ambient temperature typical 

in homes, the pressure available to move refrigerant through the capillary tube is lower, thus 

possibly leading to increased superheat and less than optimum performance. An automatic valve 

could provide optimum performance for a wider range of operating conditions, but such 

improvement is not reflected in current energy testing. DOE has eliminated this option from 

further consideration. 

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EERE-2008-BT-STD-0012 COMMENT 20
4.2.12 Off-Cycle Valve 

Off-cycle refrigerant migration reduces a refrigeration product’s efficiency by allowing 

warm and/or vapor-phase refrigerant to pass into the cabinet. A fluid control or solenoid valve 

installed after the condenser to effectively isolate the evaporator from the condenser during the 

off-cycle can be used to prevent refrigerant migration. Research has demonstrated that solenoid 

valves can yield substantial energy savings.4 Such a solenoid valve represents a possible 

reliability issue, although many wine storage products use similar solenoid valves to allow 

control of multiple compartments with a single compressor. Also, operation with an off-cycle 

valve requires that the compressor motor can start up against a substantial pressure difference. 

The starting windings of compressors that can do this reliably over the life of a refrigerator draw 

more power and hence reduce the compressor’s steady-state efficiency. The different efficiency 

levels of commercial refrigeration compressors designed for instant restart versus restart after 

pressure equalization have EER ratings which differ by 10% or more. Such a difference would 

be expected for residential compressors operating with an off cycle valve, and this difference 

would more than neutralize any benefit accrued from using the off-cycle valve. Hence, DOE has 

eliminated this option from further consideration. 

4.2.13 Reduced Energy for Automatic Defrost 

In some cases, the defrost heat supplied is more than required. Thus, energy savings can 

be achieved by reducing the defrost heat by either using smaller heaters, reducing the heater ontime, reducing the frequency of defrost, or a combination of these. In its 1995 TSD, DOE found 

that most manufacturers had already significantly reduced the electric heat for auto defrost in 

order to comply with the energy efficiency standards that became effective in 1993.5

 The percent 

of energy represented by defrost for the refrigerator-freezers tested as part of this rulemaking 

ranged from 4% to 5% for products without adaptive defrost and from 1% to 5% for products 

with adaptive defrost. It is unlikely that significant energy savings are achievable by further 

reducing the energy for automatic defrost without compromising defrost performance, except 

through use of adaptive defrost. 

4.2.14 Condenser Hot Gas Defrost 

Another method of reducing the energy required for defrost is to eliminate the need for 

electric heaters by substituting condenser hot gas in their place. In a condenser hot gas defrost 

system, the compressor continues to run and a valve opens allowing hot compressed refrigerant 

to flow to the evaporator. Many frost-free refrigerator-freezers in the 1960s and 1970s used a 

condenser hot gas defrost system. In its 1995 TSD, DOE was not able to identify data that 

demonstrated that the condenser hot gas method was more cost-effective than adaptive defrost. 

Therefore, DOE dropped the condenser gas defrost as a technology option in favor of adaptive 

defrost. 6 Hot gas defrost would potentially save energy because a large portion of the heat for 

defrost could be provided by heat generated by the compressor motor during the on-cycle rather 

than from new electricity use. The compressor is at an elevated temperature with respect to 

ambient during the on-cycle and is certainly much warmer than freezing temperature. The heat 

would be transported to the evaporator with circulating refrigerant during the defrost cycle. 

However, in spite of this potential reduction in use of electricity to provide defrost heat, the 

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EERE-2008-BT-STD-0012 COMMENT 20
energy savings potential is not well documented. Also, there are concerns regarding reliability of 

the required valve. 

4.2.15 Electronic Temperature Control 

DOE has not identified any relevant information showing the energy benefit of electronic 

temperature control. Potential benefits of electronic control when operating with single-speed 

compressors are fine-tuning of the run times and fine-tuning of the cut-in and cut-out 

temperatures. While there may be potential for incremental improvement associated with such 

fine-tuning, the lack of data supporting claims for energy savings make it difficult to properly 

analyze this option. 

4.2.16 Air-Distribution Control 

Air temperature distribution in refrigeration products with fan-forced evaporator air flow 

is generally good, in contrast with some products with cold wall or roll bond evaporators. Hence, 

it is not clear that improvements in air distribution will provide significant reduction in energy 

use. Redirection of air flows in a cabinet could potentially provide a false indication of efficient 

operation, for instance if the coldest air from the evaporator discharge is directed at the locations 

used for the energy test thermocouples. It is conceivable that valid reduction in energy use could 

occur if the air flow distribution keeps cold air away from the walls of the cabinet. However, 

there is insufficient information regarding the designs of air flow distribution systems to quantify 

potential energy savings. 

4.2.17 Alternative Refrigerants 

R-600a (isobutane) is the most logical alternative to the HFC-134a refrigerant used 

exclusively in U.S. residential refrigeration products. Isobutane is a hydrocarbon refrigerant 

which has been used for many years in refrigeration products in Europe and other foreign 

countries. The theoretical efficiency of isobutane is higher than that of HFC-134a, however, the 

U.S. refrigeration industry has not adopted hydrocarbon refrigerants (likewise for the U.S. air 

conditioning industry) due to concerns regarding flammability. Recent shifts in this viewpoint 

are the result of pressures regarding the direct global warming impact of the refrigerant rather 

than the energy use impacts. Comments from manufacturers regarding the potential for 

efficiency improvement using isobutane are mixed. In any case, it is not expected that U.S. 

manufacturers will switch to isobutane to reduce energy use and that there will be limited 

conversion unless legislation is enacted which mandates phaseouts for global warming 

substances such as HFC refrigerants. In the case of such legislation, the potential improvement in 

energy use associated with isobutane will be balanced by a potential increase in energy use 

associated with reduced resistivity of PU foam insulation made with cyclopentane blowing 

agent, the most likely replacement for currently-used HFC blowing agents. DOE will consider 

the impacts of switch to hydrocarbon refrigerants and blowing agents if such legislation is 

enacted, but DOE will not consider use of isobutane as a design option to improve efficiency in 

the absence of such legislation. 

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EERE-2008-BT-STD-0012 COMMENT 20
 

4.2.18 Component Location 

Locating the compressor at the top of the refrigerator was noted as a potential technology 

option. However, this change would increase structural requirement for the refrigerator cabinet, 

increase risk of product tip-over, and provide much less practical use of space from the consumer 

perspective. It also makes design for re-evaporation of defrost water more challenging. It is 

unlikely that the savings would justify all of these drawbacks. 

Another option is to locate the evaporator fan motor outside the cabinet to reduce internal 

loads from the heat loss of the motor. Evaporator fan motor input wattages are now in the range 

3W to 7W, with fan blade efficiency in the range 20% to 30% and motor efficiency in the range 

20% to 50%. Hence, load reduction, associated with moving the motor loss outside the cabinet, 

is only in the range 1W to 5W for the typically less than 50% of the time that the evaporator fan 

is in operation. The loss associated with the added infiltration and conduction is likely to be 

comparable to this level. Additional issues with this approach include reliability, reduced design 

flexibility, and the fact that reduction of motor losses (by using more efficient fan motors) may 

be a more effective approach to reducing the impact of the fan motor power input. 

No options for relocation of components have been identified which merit further 

consideration in the engineering analysis. 

4.2.19 Lorenz-Meutzner Cycle 

Research on Lorenz-Meutzner cycles reported in the literature involve binary mixtures 

HCFC-22/CFC-11, HCFC-22/HCFC-123, propane/n-pentane, and propane/n-butane. These 

systems achieved efficiency levels from 15 to 20 percent better than the baseline systems with 

which they were compared.7,8 Because the industry settled on the use of HFC-134a to replace 

CFC-12, interest in the Lorenz-Meutzner cycle as an alternative to conventional refrigeration 

cycles declined. All of the refrigerant combinations discussed above have specific problems, the 

first two with phaseout of constituent refrigerants CFC-11 and HCFC-22, and the last two with 

flammability of the hydrocarbon blends involved. While it is possible that HFC mixtures could 

be developed to create a viable Lorenz-Meutzner cycle refrigerator, DOE is not aware that such a 

prototype has been built and tested successfully. Hence, DOE has not considered this technology 

in the engineering analysis. 

4.2.20 Dual-Loop System 

Dual-loop systems have difficulty achieving their theoretical improvement potential due 

to the significantly reduced efficiency for smaller-capacity compressors. If the two compressors 

of a dual-loop system serving a refrigerator-freezer were sized appropriately for their respective 

loads, the freezer compressor capacity would nominally be roughly half that of a single-system 

compressor. A fresh food compressor typically operates at a capacity significantly higher than its 

nominal capacity because of the higher evaporating temperature when cooling just the fresh food 

compartment. Hence, the nominal capacity of a fresh food compartment compressor serving a 

dual-loop system is generally 30 to 40 percent that of the single-system compressor. Even with 

the efficiency improvement associated with higher evaporating temperature operation of the 

fresh food compartment compressor, this compressor still would not operate at an efficiency 

4-9 

EERE-2008-BT-STD-0012 COMMENT 20
level better than that of the single-system compressor for freezer conditions. Hence, with the 

efficiency characteristics of available compressors, it is not clear that the dual-loop architecture 

will provide any energy savings. Hence, DOE has not considered this technology in the 

engineering analysis. 

4.2.21 Two-Stage System 

In practice, a two-stage system would suffer the same disadvantages associated with a 

dual-loop system. Furthermore, it is not clear that a suitable compressor is available for the lower 

stage of such a system. DOE is not aware of any prototypes of such a system using compressors 

which their manufacturers would warrantee for such a product. Hence, DOE has not considered 

this technology in the engineering analysis. 

4.2.22 Control Valve System and Tandem System 

There are many patents covering dual-evaporator refrigerator designs. It is not clear how 

many of these were developed to improve system efficiency, since one of the benefits of using 

dual evaporators is avoiding excessively low humidity levels in the fresh food compartment. 

While there is research involving laboratory testing which shows that these technology options 

can save energy, DOE is not aware of any commercialized refrigerators using either of these 

approaches. In discussions with manufacturers none identified these options as being interesting 

approaches for energy use reduction. Further, due to the extensive patent literature discussing 

dual-evaporator systems, it is likely that products requiring dual evaporator designs would be 

restricted to the patentholders. Hence, DOE has not considered this technology in the 

engineering analysis. 

4.2.23 Ejector Refrigerator 

Energy savings have been reported for use of an ejector system in laboratory testing. In 

discussions with manufacturers there was limited familiarity with this concept and no 

acknowledgement that it has been proven through prototype testing and/or that it is an interesting 

concept for improving efficiency. Hence, DOE has not considered this technology in the 

engineering analysis. 

4.2.24 Stirling Cycle 

In principle, the efficiency of Stirling cycles could be higher than for vapor 

compression systems, but there are various technical difficulties that have so far limited the use 

of Stirling-cycle cooling to small prototype domestic refrigerators. There is no circulating 

refrigerant fluid and the hot and cold end areas are very small, which creates heat exchange 

difficulties. Heat pipes may be required to transfer heat to and from the system. A comparison of 

the performance of Stirling cycle with vapor compression compressors is shown in Figure 4.2.1 

below. The Stirling cycle data was obtained from the Global Cooling website9

 and from data 

presented at the Purdue Refrigeration Conference in 2002.10 The figure shows that Stirling 

technology is not currently ready to improve upon the efficiency of conventional technology. 

Hence, DOE has not considered this technology in the engineering analysis. 

4-10
 

EERE-2008-BT-STD-0012 COMMENT 20
0 

2 

4 

6 

8 

10 

12 

EER (Btu/hr-W) 

Conventional: Danfoss TTE4.6FK, Nominal 4.62 EER 

Conventional: Tecumseh TPG1370YXA, Nominal 5.82 EER 

Stirling: Purdue 2002 Paper 

Stirling: Global Cooling M100 

40 60 80 100 120 140 160 

Temperature Lift (F) 

Figure 4.2.1 Comparison of Stirling and Vapor Compression Technologies 

4.2.25 Thermoelectric 

 Thermoelectric cooling technologies currently do not achieve efficiency levels which 

make them attractive as a design option for improving residential refrigeration energy efficiency. 

As an example, DOE tested a thermoelectric refrigerator as part of the reverse engineering effort 

of this rulemaking. This refrigerator was a Haier model HRT02WNC, a 1.7 cuft all-refrigerator. 

In an 80 °F ambient with the system operating at full power, this unit was able to cool the 

interior to 47 °F while drawing 50W total. The fans serving the inside and outside heat sinks of 

the thermoelectric unit are rated at a voltage of 12 Volts and currents of 0.13 Amps and 0.16 

Amps respectively, and a control board power input of 1W is assumed. The thermal load for the 

cabinet was estimated as 12 W. Hence the thermoelectric module EER was 0.9 at a temperature 

lift of at most 33 °F, an order of magnitude less than is achieved by conventional technology. 

Hence, DOE has not considered this technology in the engineering analysis. 

4.2.26 Thermoacoustic 

While research suggests that thermoacoustic cooling systems could achieve respectable 

efficiencies, the technology has not reached a level of maturity sufficient for serious 

consideration as the basis for efficiency improvement in residential refrigeration products. 

Hence, DOE has not considered this technology in the engineering analysis. 

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EERE-2008-BT-STD-0012 COMMENT 20
4.3 REMAINING TECHNOLOGIES 

After eliminating those technologies that have no effect or do not increase EER and 

screening out those technologies that that do not meet the requirements of sections 4(a)(4) and 

5(b) of the Process Rule, DOE is considering the technologies in the following list. 

• Increased Insulation Thickness 

• Vacuum Insulation Panels (VIPs) 

• Variable Anti-sweat Heating 

• Improved Compressor Efficiency 

• Variable Speed Compressors 

• Increased heat exchanger area (extension of surface area or addition of coil rows). 

• Use of forced convection condenser (for upright freezers) 

• Improved efficiency fan motors (brushless DC) 

• Adaptive Defrost 

4-12
 

EERE-2008-BT-STD-0012 COMMENT 20
 

 

 

 

 

 

 

 

 

 

 

 

REFERENCES 

1	 Pisipati, J.S. and Godbey, J.A. “Performance of Carbon Black-Containing Polyurethane 

Foam in Domestic Refrigerators,” Journal of Cellular Plastics, 1996. Vol. 32, No. 2, 108­

138. <http://cel.sagepub.com/cgi/content/abstract/32/2/108> 

2	 American Council for an Energy-Efficient Economy. "One kWh/day Refrigerator," Emerging 

Technologies & Practices, 2004. Washington, DC. 

3	 Belko, John. Novel Fan Design Offers Energy Savings to Refrigeration Market, 2007. A.O. 

Smith Electrical Products Company. 

<http://www.aosmithmotors.com/pdf/documents/pax%20fan%20evap%20%20technical%20 

paper%20_j%20belko_-2007.pdf> (Accessed September 26, 2007.) 

4	 Coulter, W.H. and Bullard, C.W. “ An Experimental Analysis of Cycling Losses in Domestic 

Refrigerator-Freezers,” ASHRAE Transactions, 1997. Vol. 103, Pt. 1. 

5	 U.S. Department of Energy-Office of Codes and Standards. Technical Support Document: 

Energy Efficiency Standards for Consumer Products: Refrigerators, Refrigerator-Freezers, 

and Freezers, July 1995. Washington, DC. DOE/EE-0064. p. 3-8. 

6	 U.S. Department of Energy-Office of Codes and Standards. Technical Support Document: 

Energy Efficiency Standards for Consumer Products: Refrigerators, Refrigerator-Freezers, 

and Freezers, July 1995. Washington, DC. DOE/EE-0064. p. 3-8. 

7	 Lorenz, A. and Meutzner, K. “On application of non-azeotropic two component refrigerants 

in domestic refrigerator and home freezers,” Proceedings of the XIV International Congress 

of Refrigeration, 1975. Moscow. 

8	 Liu, Z., Haider, I., and Radermacher, R. “Simulation and Test Results of Hydrocarbon 

Mixtures in a Modified-Lorenz-Meutzner Cycle Domestic Refrigerator,” HVAC&R 

Research, Vol. 1, No. 2, April,, 1995. 

9	 http://www.globalcooling.nl/technologyoverview.html#perform 

10	 Janssen, M. and P.Beks, “Measurement and Application of Performance Characteristics of a 

Free Piston Stirling Cooler”, presented at the Ninth International Refrigeration and Air 

Conditioning Conference at Purdue, 2002. 

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CHAPTER 5: ENGINEERING ANALYSIS 

TABLE OF CONTENTS 

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

5.2 PRODUCT CLASSES ANALYZED.............................................................................. 5-1 

5.3 METHODOLOGY OVERVIEW .................................................................................... 5-2 

5.4 EFFICIENCY LEVELS................................................................................................... 5-3 

5.4.1 Baseline Units based on the Current Test Procedure........................................... 5-3 

5.4.2 Baseline Efficiency Definitions Based on the Expected Test Procedure ............ 5-6 

5.4.2.1 Data Illustrating the Impact of Test Procedure Changes ......................... 5-7 

5.4.2.2 Establishment of Baseline Energy—Adjusted Volume
 

Relationships Based on the New Test Procedure .................................. 5-11 

5.4.2.3 Investigation of the Slope of the Energy Use Curve.............................. 5-14 

5.4.3 Incremental Efficiency Levels ........................................................................... 5-15 

5.4.4 Maximum Technology Level............................................................................. 5-16 

5.5 DATA COLLECTION .................................................................................................. 5-18 

5.5.1 Manufacturer-Submitted Shipment and Cost Data from AHAM...................... 5-18 

5.5.2 Component Vendor Data ................................................................................... 5-19 

5.5.3 Reverse Engineering .......................................................................................... 5-20 

5.5.3.1 Selection of Products for Reverse Engineering ..................................... 5-20 

5.5.3.2 Collection of Energy Modeling Data..................................................... 5-22 

5.5.4 Manufacturer Interviews.................................................................................... 5-23 

5.5.5 Energy testing .................................................................................................... 5-23 

5.6 MANUFACTURING COST MODELING................................................................... 5-24 

5.6.1 Generation of Bills of Materials ........................................................................ 5-24 

5.6.2 Cost Structure of the Spreadsheet Models......................................................... 5-25 

5.6.3 Cost Model and Definitions............................................................................... 5-25 

5.6.3.1 Cost Definitions ..................................................................................... 5-26 

5.6.4 Cost Model Assumptions Overview .................................................................. 5-26 

5.6.4.1 Fabrication Estimates............................................................................. 5-27 

5.6.4.2 Production Volumes Assumptions......................................................... 5-28 

5.6.4.3 Factory Parameters Assumptions........................................................... 5-28 

5.6.4.4 Material Cost Assumptions.................................................................... 5-28 

5.6.5 Manufacturing Production Cost......................................................................... 5-30 

5.6.6 Incremental Cost Estimates................................................................................ 5-31 

5.6.6.1 Overhead and Depreciation Costs.......................................................... 5-31 

5.6.6.2 Depreciation Costs for Insulation Thickness Increases ......................... 5-32 

5.6.6.3 G&A and Profit...................................................................................... 5-33 

5.7 ENERGY MODELING................................................................................................. 5-34 

5.7.1 Energy Model development............................................................................... 5-34 

5.7.2 Supplemental Spreadsheet Models .................................................................... 5-35 

5.7.3 Development and Calibration of ERA Current Energy Test Models ................ 5-36 

5.7.4 Adjustments to Energy Models to Represent Baseline Products Tested 

Under the Proposed Test Procedure................................................................... 5-40 

5-i 

EERE-2008-BT-STD-0012 COMMENT 20
5.8 DESIGN OPTIONS....................................................................................................... 5-42 

5.8.1 Increased Insulation Thickness.......................................................................... 5-43 

5.8.2 Vacuum-Insulated Panels................................................................................... 5-44 

5.8.3 Improved Compressor Efficiency...................................................................... 5-45 

5.8.4 Variable-Speed Compressor .............................................................................. 5-48 

5.8.5 Increased Evaporator Surface Area ................................................................... 5-50 

5.8.6 Increased Condenser Surface Area .................................................................... 5-50 

5.8.7 Brushless DC Fan Motors.................................................................................. 5-50 

5.8.8 Adaptive Defrost................................................................................................ 5-51 

5.8.9 Variable Anti-Sweat Heater Control.................................................................. 5-52 

5.8.10 Forced Convection Condenser........................................................................... 5-53 

5.9 ENGINEERING ANALYSIS RESULTS ..................................................................... 5-53 

5.9.1 DOE Cost-Efficiency Curves............................................................................. 5-53 

5.9.2 AHAM Incremental Cost Data .......................................................................... 5-57 

5.9.2.1 Product Class 3 ...................................................................................... 5-59 

5.9.2.2 Product Class 5 ...................................................................................... 5-62 

5.9.2.3 Product Class 7 ...................................................................................... 5-64 

5.9.2.4 Product Class 9 ...................................................................................... 5-66 

5.9.2.5 Product Class 11 .................................................................................... 5-68 

LIST OF TABLES 

Table 5.2.1 Product Classes Analyzed in Engineering Analysis ............................................... 5-2 

Table 5.4.1 Refrigerator, Refrigerator-Freezer, and Freezer Energy Conservation 

Standards and Proposed Baseline Model Efficiencies............................................ 5-5 

Table 5.4.2 Expected Cabinet Temperature Changes for the DOE Test Procedure .................. 5-6 

Table 5.4.3 Volume Adjustment Factors ................................................................................... 5-6 

Table 5.4.4 Compartment Volume Calculation Changes .......................................................... 5-7 

Table 5.4.5 Compartment Temperature and Adjusted Volume Change Data provided by 

AHAM—Current Test ............................................................................................ 5-8 

Table 5.4.6 Compartment Temperature and Adjusted Volume Change Data provided by 

AHAM--Proposed Test........................................................................................... 5-9 

Table 5.4.7 Compartment Temperature and Adjusted Volume Change Data provided by 

AHAM—Impact ................................................................................................... 5-10 

Table 5.4.8 Energy Use Impact of Compartment Temperature Changes: Data Developed 

by DOE ................................................................................................................. 5-11 

Table 5.4.9 Approach for Establishing Baseline Energy--Adjusted Volume
 

Relationships......................................................................................................... 5-12 

Table 5.4.10 New Baseline Energy Consumption based on Proposed Test Procedure............. 5-14 

Table 5.4.11 DOE Assessment of the Slope of the Energy Use Curve ..................................... 5-15 

Table 5.4.12 Incremental Efficiency Levels (% Energy Use Less than Baseline) .................... 5-16 

Table 5.4.13 Maximum Available Levels (%Energy Use Less than Baseline)......................... 5-16 

Table 5.4.14 Maximum Technology Levels.............................................................................. 5-18 

Table 5.5.1 Component Vendors Contacted by DOE during Engineering Analysis............... 5-20 

Table 5.5.2 Selected Units for Reverse-Engineering and Energy Testing............................... 5-21 

5-ii 

EERE-2008-BT-STD-0012 COMMENT 20
Table 5.5.3 Additional Thermocouple Locations for Energy Test .......................................... 5-24 

Table 5.6.1 Cost Model In-House Manufacturing Operation Assumptions ............................ 5-27 

Table 5.6.2 Refrigerator & Freezer Factory Parameter Assumptions...................................... 5-28 

Table 5.6.3 Five-Year Metal Prices (2003-2008) .................................................................... 5-29 

Table 5.6.4 Most Prevalent Resin Prices as of December 2007 .............................................. 5-30 

Table 5.6.5 Overhead and Depreciation Cost Ratios............................................................... 5-32 

Table 5.6.6 Greenfield Depreciation Costs per Product .......................................................... 5-33 

Table 5.8.1 Design Options by Product Class ......................................................................... 5-43 

Table 5.8.2 Teardown Product Fan Power Input ..................................................................... 5-51 

Table 5.9.1 DOE Incremental Costs ........................................................................................ 5-54 

Table 5.9.2 AHAM Incremental Cost Data for Product Class 3.............................................. 5-59 

Table 5.9.3 AHAM Incremental Cost Data for Product Class 5.............................................. 5-62 

Table 5.9.4 AHAM Incremental Cost Data for Product Class 7.............................................. 5-64 

Table 5.9.5 AHAM Incremental Cost Data for Product Class 9.............................................. 5-66 

Table 5.9.6 AHAM Incremental Cost Data for Product Class 11............................................ 5-68 

LIST OF FIGURES 

Figure 5.3.1 Flow Diagram of Engineering Analysis Methodology........................................... 5-3 

Figure 5.4.1 Maximum Efficiency Levels Available by Product Class.................................... 5-17 

Figure 5.6.1 Full Production Costs............................................................................................ 5-30 

Figure 5.7.1 ERA Analysis for Refrigerator-Freezers Compared with EnergyGuide 

Labels and Energy Test Measurements ................................................................ 5-38 

Figure 5.7.2 ERA Analysis for Freezers Compared with EnergyGuide Labels and Energy 

Test Measurements ............................................................................................... 5-39 

Figure 5.7.3 ERA Analysis for Compact Refrigerators and Freezers Compared with 

EnergyGuide Labels and Energy Test Measurements.......................................... 5-39 

Figure 5.8.1 Compressor Efficiency Data................................................................................. 5-46 

Figure 5.8.2 Incremental Cost for Single-Speed Compressors for Standard-Size Products ..... 5-47 

Figure 5.8.3 Efficiency Curve for Low Capacity Compressors................................................ 5-48 

Figure 5.9.1 Incremental Manufacturer Selling Price for Standard-Size RefrigeratorFreezers................................................................................................................. 5-55 

Figure 5.9.2 Incremental Manufacturer Selling Price for Standard-Size Freezers ................... 5-56 

Figure 5.9.3 Incremental Manufacturer Selling Price for Compact Refrigerators and 

Freezers................................................................................................................. 5-57 

Figure 5.9.4 Incremental Cost Curves for Product Class 3....................................................... 5-60 

Figure 5.9.5 Incremental Cost Curves for Product Class 5....................................................... 5-63 

Figure 5.9.6 Incremental Cost Curves for Product Class 7....................................................... 5-65 

Figure 5.9.7 Incremental Cost Curves for Product Class 9....................................................... 5-67 

Figure 5.9.8 Incremental Cost Curves for Product Class 11..................................................... 5-69 

Figure 5.9.9 Product Class 11 Refrigerators listed in the ENERGY STAR Database.............. 5-69 

5-iii 

EERE-2008-BT-STD-0012 COMMENT 20
CHAPTER 5. ENGINEERING ANALYSIS 

5.1 INTRODUCTION 

The engineering analysis establishes the relationship between manufacturer 

production cost and energy consumption for the refrigerators, refrigerator-freezers, and 

freezers covered in this rulemaking. The “cost-efficiency” relationship serves as the basis 

for cost-benefit calculations in terms of individual customers, manufacturers, and the 

Nation, from which the most economically-justified, technically feasible standard level is 

ultimately determined. 

The inputs into the engineering analysis include baseline characteristics for each 

product class addressed in the market and technology assessment (chapter 3), the design 

options from the screening analysis (chapter 4), 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 independent of cabinet volume, which will be used in the life-cycle and 

payback period analyses (chapter 8). 

This chapter covers the product classes DOE analyzed, and the methodology used 

by DOE to develop manufacturing costs, energy consumption, and extend the analysis to 

low-volume product classes, as well as the results of these analyses. 

5.2 PRODUCT CLASSES ANALYZED 

In the engineering analysis for the preliminary notice of proposed rulemaking 

(Pre-NOPR), DOE analyzed the seven product classes listed in Table 5.2.1. DOE 

considers these classes to be representative of products currently shipped by the 

residential refrigerator, freezer, and refrigerator-freezer industry based on total shipments. 

These product classes represent close to 90% of the shipments of refrigerators, 

refrigerator-freezers, and freezers. DOE did not directly analyze all covered product 

classes in order to carry out the analysis as efficiently as possible. DOE proposes 

extrapolation of energy standards to the remaining product classes as described in section 

2.15 of chapter 2. 

5-1 

EERE-2008-BT-STD-0012 COMMENT 20
Table 5.2.1 Product Classes Analyzed in Engineering Analysis 

Product 

Class Equipment Description 

3 Refrigerator-freezers—automatic defrost with top-mounted freezer without 

TTD ice service 

5 Refrigerator-freezers—automatic defrost with bottom-mounted freezer without 

TTD ice service 

7 Refrigerator-freezers—automatic defrost with side-mounted freezer with TTD 

ice service 

9 Upright freezers with automatic defrost 

10 Chest freezers and all other freezers except compact freezers 

11 Compact refrigerators and refrigerator-freezers with manual defrost 

18 Compact chest freezers 

5.3 METHODOLOGY OVERVIEW 

This section describes the analytical methodology DOE used in the engineering 

analysis. In this rulemaking, DOE has adopted a combined efficiency level, design option 

approach to developing cost-efficiency curves. DOE established efficiency levels defined 

on percent energy use lower than that of baseline efficiency products in order to allow 

comparison of information developed from different sources. However, DOE’s analysis 

is based on the efficiency improvements associated with groups of design options. 

Figure 5.3.1 presents the steps in the analysis and illustrates how they contribute 

to developing the cost-efficiency curves. The process begins with data collection and 

ends with the incremental cost curve results. 

As input to the analysis, DOE requested incremental cost-efficiency data from the 

industry. The Association of Home Appliance Manufacturers (AHAM) provided 

aggregated incremental cost data for a number of the product classes under analysis. This 

information was supplemented by analytically-derived cost-efficiency curves for the 

seven product classes listed in Table 5.2.1. 

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 

reverse-engineering of current products, and interviewed component vendors of 

compressors, fan motors, insulation, and heat exchangers. DOE also conducted 

interviews with manufacturers, using an engineering questionnaire which is reproduced 

in appendix 5-A. 

5-2 

EERE-2008-BT-STD-0012 COMMENT 20
Figure 5.3.1 Flow Diagram of Engineering Analysis Methodology 

 Cost information from the vendor interviews and engineering questionnaires 

provided input to the manufacturing cost model. Incremental costs associated with 

specific design options were calculated using the cost model. Energy use reduction was 

modeled with a modified version of the established EPA Refrigerator Analysis (ERA) 

program which was used in the previous refrigerator rulemaking. The 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 energy efficiency curves presented in this chapter. 

5.4 EFFICIENCY LEVELS 

5.4.1 Baseline Units based on the Current Test Procedure 

DOE selected baseline units as reference points for all of the product classes, 

against which DOE determined changes resulting from use of energy saving design 

options. The baseline unit in each product class represents the basic characteristics of 

equipment in that class. A baseline unit is a unit that just meets current required energy 

conservation standards and provides basic consumer utility. 

As discussed in chapter 3, DOE has initiated a rulemaking to revise the energy 

test procedure for refrigerators, refrigerator-freezers, and freezers. Some of the 

anticipated changes to the test procedure such as changes in compartment temperatures 

will result in changes in the measured energy consumption. The test procedure change 

will also affect the measured size of the refrigerators, expressed as adjusted volume. 

5-3 

EERE-2008-BT-STD-0012 COMMENT 20
Since the maximum energy use for residential refrigeration products is expressed as a 

function of adjusted volume, the change in adjusted volume also affects the definition of 

baseline products. This section discusses definitions of baseline units for the engineering 

analysis based on the current test procedure, while the next section discusses modified 

definitions for baseline refrigeration products based on the expected revised test 

procedure. 

For this rulemaking, DOE established baseline efficiency levels as the current 

federal energy conservation standards, expressed as maximum annual energy 

consumption as a function of the product’s adjusted volume, as shown in Table 5.4.1. 

These definitions are based on testing according to the current energy test procedure. 

5-4 

EERE-2008-BT-STD-0012 COMMENT 20
 

 

 

 

Table 5.4.1 Refrigerator, Refrigerator-Freezer, and Freezer Energy Conservation 

Standards and Proposed Baseline Model Efficiencies 

Product Class Equations for Maximum 

Energy Use (kWh/yr) 

1. Refrigerators and refrigerator-freezers with manual defrost. 8.82AV + 248.4 

0.31av + 248.4 

2. Refrigerator-freezer—partial automatic defrost. 8.82AV + 248.4 

0.31av + 248.4 

3. Refrigerator-freezer—automatic defrost with top-mounted freezer without 

TTD ice service and all-refrigerator—automatic defrost. 

9.80AV + 276.0 

0.35av + 276.0 

4. Refrigerator-freezers—automatic defrost with side-mounted freezer without 

TTD ice service. 

4.91AV + 507.5 

0.17av + 507.5 

5. Refrigerator-freezers—automatic defrost with bottom-mounted freezer 

without TTD ice service. 

4.60AV + 459.0 

0.16av + 459.0 

6. Refrigerator-freezers—automatic defrost with top-mounted freezer with 

TTD ice service. 

10.20AV + 356.0 

0.36av + 356.0 

7. Refrigerator-freezers—automatic defrost with side-mounted freezer with 

TTD ice service. 

10.10AV + 406.0 

0.36av + 406.0 

8. Upright freezers with manual defrost. 7.55AV + 258.3 

0.27av + 258.3 

9. Upright freezers with automatic defrost. 12.43AV + 326.1 

0.44av + 326.1 

10. Chest freezers and all other freezers except compact freezers. 9.88AV + 143.7 

0.35av + 143.7 

11.Compact refrigerators and refrigerator-freezers with manual defrost. 10.70AV + 299.0 

0.38av + 299.0 

12. Compact refrigerator-freezer—partial automatic defrost. 7.00AV + 398.0 

0.25av + 398.0 

13. Compact refrigerator-freezers—automatic defrost with top-mounted 

freezer and compact all-refrigerator—automatic defrost. 

12.70AV + 355.0 

0.45av + 355.0 

14. Compact refrigerator-freezers—automatic defrost with side-mounted 

freezer. 

7.60AV + 501.0 

0.27av + 501.0 

15. Compact refrigerator-freezers—automatic defrost with bottom-mounted 

freezer. 

13.10AV + 367.0 

0.46av + 367.0 

16. Compact upright freezers with manual defrost. 9.78AV + 250.8 

0.35av + 250.8 

17. Compact upright freezers with automatic defrost. 11.40AV + 391.0 

0.40av + 391.0 

18. Compact chest freezers. 10.45AV + 152.0 

0.37av + 152.0 

5A. Refrigerator-freezer—automatic defrost with bottom-mounted freezer with 

TTD ice service. 

5.0AV + 539.0 

0.18av + 539.0 

10A. Chest freezers with automatic defrost. 14.76AV + 211.5 

0.52av + 211.5 

AV= adjusted volume in cubic feet; av = adjusted volume in liters; 

Refrigerator-Freezers: AV = fresh food internal volume + 1.63 * freezer internal volume 

Freezers: AV = 1.73 * freezer internal volume 

Refrigerators (single-door): AV = fresh food internal volume + 1.44 * freezer internal volume 

All-Refrigerators: AV = internal volume 

5-5 

EERE-2008-BT-STD-0012 COMMENT 20
5.4.2 Baseline Efficiency Definitions Based on the Expected Test Procedure 

As discussed in chapter 3, DOE expects to propose revisions in the energy test 

procedure to harmonize with expected test temperatures under consideration for IEC test 

procedure 62552 and to simplify calculation of refrigerated volumes. The expected test 

temperature changes are summarized in Table 5.4.2 below. 

Table 5.4.2 Expected Cabinet Temperature Changes for the DOE Test Procedure 

Fresh Food Compartment 

Temperature °F 

Freezer Compartment 

Equipment Type Temperature °F

Current Expected Current Expected 

Refrigerator-Freezer 45 39 5 0 

All-Refrigerator 38 39 Not Applicable 

Refrigerator w/ Freezer 

Compartment 45 39 15 15 (No Change) 

Freezer Not Applicable 0 0 (No 

Change) 

The temperature changes also impact the volume adjustment factor used to 

determine the adjusted volume. This factor is multiplied by the freezer compartment 

volume in the adjusted volume calculation. Current and expected volume adjustment 

factors are summarized in Table 5.4.3 below. 

Table 5.4.3 Volume Adjustment Factors 

Product 

Refrigerator-Freezer 

Current Test Procedure 

1.63 

Expected Test Procedure 

Revisions 

1.76 

Basic Refrigerator* 1.44 1.47 

Freezer 1.73 1.76 

All-Refrigerator** 1.00 1.00 

*A basic refrigerator is a single-door refrigerator with a freezer compartment with 

volume greater than 0.5 ft3

. 

**An all-refrigerator can have a freezer compartment with volume less than 0.5 ft3. 

The key changes in the volume measurement calculation between the current test 

procedure and the expected revised test procedure are summarized in Table 5.4.4 below. 

Adjusted volume will be impacted both by the change in the volume adjustment factor 

and the change in the volume measurement. 

5-6 

EERE-2008-BT-STD-0012 COMMENT 20
Table 5.4.4 Compartment Volume Calculation Changes 

Item AHAM HRF-1-1979 AHAM HRF-1-2008 

Expected 

Effect on 

Volume 

Automatic Ice Maker 

Storage Bin Included (4.2.1.1a) 

Would be included 

under “removable 

containers” but 

dispenser MAY NOT 

be included 

None* 

Ice Makers Included (4.2.1.1a) No Mention None* 

Water Coolers Included (4.2.1.1a) No Mention None* 

Door Shelf Fronts and 

Bottoms Included (4.2.1.1b) 

Shelves molded into 

the inner door panel 

NOT included (4.2.2) 

Decrease 

Volume between the 

Deductible Door Dikes 

and Cabinet Breaker 

Strips or Adjacent 

Liner Wall 

Not Included 

(4.2.1.2d) 

No mention of 

exclusion, so probably 

included. 

Increase 

Shelf Hangers & Shelf 

and Pan Rails 

Not included for 

fixed projections if 

collective volume is 

>0.05 ft3

 (4.2.1.2e) 

Could be interpreted as 

part of shelving and 

would thus be 

included. 

Increase 

*Although AHAM HRF-1-2008 either doesn’t mention this item or is not fully 

clear regarding its treatment for the volume calculation, it is expected that manufacturers 

would use the AHAM HRF-1-1979 approach. 

5.4.2.1 Data Illustrating the Impact of Test Procedure Changes 

The different compartment temperatures of the expected revised energy test procedure 

will change test energy use for refrigerators and refrigerator-freezers. In addition, both 

the impact of the modified temperatures on the adjusted volume and the modified volume 

calculation method will change adjusted volumes. For these reasons, it is necessary to 

establish modified relationships between energy use and adjusted volume to define 

baseline products. AHAM provided data for a number of the product classes, presented in 

Table 5.4.5 through Table 5.4.7 below (this is referred to as the AHAM TP Change data). 

The AHAM TP Change data for product classes 11 and 13 both show energy use 

reductions, indicating that the products represented by these data are primarily allrefrigerators. AHAM was not able to separately provide data for the all-refrigerators of 

these product classes, because insufficient data was provided by manufacturers for 

aggregation. 

5-7 

EERE-2008-BT-STD-0012 COMMENT 20
Additional data sources which provide indication of the impacts of the test 

temperature changes for standard-size refrigerator-freezers include (1) energy test 

measurements for the refrigerator-freezers tested as part of this rulemaking, and (2) 

calculation of the energy impacts using ERA, the energy modeling tool used for this 

rulemaking. The energy use impacts indicated by these sources are shown in Table 5.4.8. 

DOE conducted these energy tests and calculations for three products of each of the 

seven analyzed product classes (see Section 5.5.3.1 for discussion on selection of 

products for reverse engineering and energy testing). 

Table 5.4.5 Compartment Temperature and Adjusted Volume Change Data 

provided by AHAM—Current Test 

Product 

Class 

Fresh Food 

Volume 

Freezer 

Volume 

Adjusted 

Volume 

Energy 

Use 

Average 12.82 5.02 20.92 420 

3 (R-F) Standard Deviation 3.54 1.82 6.53 55 

Number of Samples 19 19 19 19 

Average 19.26 19.26 374 

3A (AR) Standard Deviation 3.4 3.4 54 

Number of Samples 11 11 11 

Average 14.21 5.15 22.62 493 

5 Standard Deviation 1.85 1.02 3 55 

Number of Samples 18 18 18 18 

Average 15.77 9.32 30.95 617 

7 Standard Deviation 1.61 0.87 2.53 68 

Number of Samples 24 24 24 24 

Average 16.85 29.14 603 

9 Standard Deviation 4.88 8.45 136 

Number of Samples 18 18 18 

Average 4.38 4.65 334 

11 Standard Deviation 1.38 1.38 44 

Number of Samples 13 13 13 

Average 4.75 4.77 296 

13 Standard Deviation 

Number of Samples 

1.18 1.15 77 

12 12 12 

Note: R-F refers to refrigerator-freezers; AR refers to all-refrigerators. 

5-8 

EERE-2008-BT-STD-0012 COMMENT 20
Table 5.4.6 Compartment Temperature and Adjusted Volume Change Data 

provided by AHAM--Proposed Test 

Product 

Class 

Fresh Food 

Volume 

Freezer 

Volume 

Adjusted 

Volume 

Energy 

Use 

Average 12.79 4.96 21.44 472 

3 (R-F) Standard Deviation 3.51 1.78 6.59 53 

Number of Samples 19 19 19 18 

Average 19.51 19.51 364 

3A (AR) Standard Deviation 3.51 3.51 53 

Number of Samples 11 11 11 

Average 14.42 5.25 23.12 582 

5 Standard Deviation 1.88 1 3.01 68 

Number of Samples 18 18 18 18 

Average 15.95 9.01 31.45 702 

7 Standard Deviation 1.79 0.75 2.49 82 

Number of Samples 24 24 24 24 

Average 16.84 29.47 603 

9 Standard Deviation 5.04 8.73 136 

Number of Samples 18 18 18 

Average 4.34 4.61 324 

11 Standard Deviation 1.36 1.36 48 

Number of Samples 13 13 13 

Average 4.8 4.83 285 

13 Standard Deviation 

Number of Samples 

1.23 1.2 73 

12 12 12 

Note: R-F refers to refrigerator-freezers; AR refers to all-refrigerators. 

5-9 

EERE-2008-BT-STD-0012 COMMENT 20
Table 5.4.7 Compartment Temperature and Adjusted Volume Change Data 

provided by AHAM—Impact 

Product 

Class 

Fresh Food 

Volume 

Freezer 

Volume 

Adjusted 

Volume 

Energy 

Use 

Average -0.1% -1.1% 2.8% 12.4% 

3 (R-F) Standard Deviation 0.6% 0.9% 2.3% 6.9% 

Number of Samples 19 19 19 18 

Average 1.2% 1.2% -2.6% 

3A (AR) Standard Deviation 1.0% 1.0% 1.1% 

Number of Samples 11 11 11 

Average 1.5% 2.2% 2.2% 18.2% 

5 Standard Deviation 1.2% 2.2% 1.2% 3.7% 

Number of Samples 18 18 18 18 

Average 1.0% -3.1% 1.6% 14.0% 

7 Standard Deviation 2.0% 4.6% 2.0% 6.7% 

Number of Samples 24 24 24 24 

Average -0.4% 0.9% 0.0% 

9 Standard Deviation 2.5% 2.2% 0.0% 

Number of Samples 18 18 18 

Average -0.7% -0.6% -3.1% 

11 Standard Deviation 1.9% 1.6% 1.4% 

Number of Samples 13 13 13 

Average 0.9% 1.0% -3.6% 

13 Standard Deviation 

Number of Samples 

1.6% 1.4% 0.8% 

12 12 12 

Note: R-F refers to refrigerator-freezers; AR refers to all-refrigerators. 

5-10
 

EERE-2008-BT-STD-0012 COMMENT 20
Table 5.4.8 Energy Use Impact of Compartment Temperature Changes: Data 

Developed by DOE 

Product 

Class 

3 

Product Description 

16 ft3 Top-Mount R-F 

Impact based on 

energy 

measurements 

19.1% 

Impact based on 

ERA modeling 

14.2% 

21 ft3

 Top-Mount R-F 27.7% 16.0% 

21 ft3 E* Top-Mount R-F 26.6% 14.1% 

5 18.5 ft3

 E* Bottom-Mount R-F 12.5% 22.1% 

25 ft3 E* Bottom-Mount R-F 1 27.6% 13.8% 

25 ft3 E* Bottom-Mount R-F 2 17.3% 14.4% 

4 22 ft3

 Side-Mount R-F† 17.7% 12.5% 

7 26 ft3

 Side-Mount R-F 24.5% 12.4% 

26 ft3 E* Side-Mount R-F 25.0% 12.2% 

11 1.7 ft3

 Compact Refrigerator -4.5% -2.4% 

4.0 ft3 Compact Refrigerator Not Tested 13.4% 

†This product was thought to be product class 7 when purchased. 

The AHAM TP Change data shows reasonable agreement with the DOE modeled 

energy use impacts. However, the DOE energy measurements indicate a higher 

sensitivity to the temperature change of the new test procedure. The AHAM data shows 

that there can be significant variation in the sensitivity of different refrigerator-freezer 

products to the test temperature changes, particularly for product classes 3 and 7. The two 

compact refrigerators of Table 5.4.8 exhibit different responses to the compartment 

temperature change because the 1.7 ft3

 refrigerator has a freezer compartment smaller 

than 0.5 ft3

 and is tested as an all-refrigerator, while the 4.0 ft3 refrigerator has a freezer 

compartment just larger than 0.5 ft3, requiring that it be tested as a basic refrigerator. 

5.4.2.2 Establishment of Baseline Energy—Adjusted Volume Relationships 

Based on the New Test Procedure 

The available data to inform the establishment of baseline energy versus adjusted 

volume relationships based on the expected revised test procedure is discussed in Section 

5.4.2.1. While this data does not address every product class, DOE proposes to use it as 

the basis for establishing the baseline relationships. The approach DOE used to develop 

these relationships for all the product classes is summarized in Table 5.4.9 below. Note 

that product classes 1, 3, 11, and 13 are split because, while the all-refrigerators have 

reduced energy use with the new test procedure, the products which include freezers have 

significantly higher energy use. This applies to product class 11, since many of these 

units have freezer compartments smaller than 0.5 ft3

, which allows them to be classified 

and tested as all-refrigerators rather than basic refrigerators. The test procedure impact of 

this classification is that the refrigerator compartment temperature will be raised for allrefrigerators, while it will be reduced for basic refrigerators under the proposed test 

procedure. 

5-11
 

EERE-2008-BT-STD-0012 COMMENT 20
Table 5.4.9 Approach for Establishing Baseline Energy--Adjusted Volume 

Relationships 

Product Class 

1 

Approach 

Use modeling with ERA for temperature, assume negligible 

adjusted volume impact based on AHAM data for PC11. 

1A 

(All-Refrigerators) 

Use AHAM TP Change aggregated data of product class 3 allrefrigerators. 

2 Trend consistent with PC1. 

3 (RefrigeratorFreezers) Use AHAM TP Change aggregated data. 

3A 

(All-Refrigerators) 

Use AHAM TP Change aggregated data. 

4 Use AHAM TP Change aggregated data of product class 7. 

5 Use AHAM TP Change aggregated data. 

5A Use AHAM TP Change aggregated data of product class 5. 

6 Use AHAM TP Change aggregated data of product class 3 

refrigerator-freezers. 

7 Use AHAM TP Change aggregated data. 

8 (volume only) Assume negligible volume impact due to simplicity of manual 

defrost freezer interior. 

9 (volume only) Use AHAM TP Change aggregated data. 

10 (volume only) Assume negligible impact due to simplicity of manual defrost 

freezer interior. 

10A (volume only) Use AHAM TP Change aggregated data for PC9. 

11 Use modeling with ERA for temperature, assume negligible 

adjusted volume impact based on AHAM data.* 

11A 

(All-Refrigerators) 

Use modeling with ERA for temperature, assume negligible 

adjusted volume impact based on AHAM data.* 

12 Trend consistent with PC11. 

13 (RefrigeratorFreezers) Use AHAM TP Change aggregated data of product class 3 

refrigerator-freezers.* 

13A 

(All-Refrigerators) 

Use AHAM TP Change aggregated data of product class 3 allrefrigerators.* 

14 Use AHAM TP Change aggregated data of product class 7. 

15 Use AHAM TP Change aggregated data of product class 5. 

16 (volume only) Assume negligible volume impact due to simplicity of manual 

defrost freezer interior. 

17 (volume only) Use AHAM TP Change aggregated data for PC9. 

18 (volume only) Assume negligible volume impact due to simplicity of manual 

defrost freezer interior. 

*The AHAM energy use increase data cannot be used for this product class, 

because it is not known how many of these products are all-refrigerators. 

5-12 

EERE-2008-BT-STD-0012 COMMENT 20
 

 

Note: For product classes 8, 10, 16, and 18, while the volume impact is assumed 

to be negligible, the adjusted volume increases according to the increase in the volume 

adjustment factor. 

The methodology for determining new baseline energy—adjusted volume curves 

given the data indicating the impacts on the energy use and adjusted volume for a given 

product class is as follows. The proposed energy use and the current energy use for a 

product are represented as being proportional using an Energy Standard Adjustment 

Factor (ESAF). 

BEC = ESAF × BEC Equation 5.4.1 NEWTP CURTP 

Where: 

BECNEWTP = Baseline energy consumption using the new test procedure; 

BECCURTP = Baseline energy consumption using the current test procedure. 

The ESAF is considered to be a function only of product class. Dependence on 

adjusted volume or efficiency level cannot be determined based on the available data. 

Similarly, the adjusted volume for a product under the proposed test procedure is 

related to the adjusted volume under the current test procedure using a Volume 

Calculation Adjustment Factor (VCAF). 

AV = VCAF × AV Equation 5.4.2 NEWTP CURTP 

Where: 

AVNEWTP = Adjusted Volume using the new test procedure; 

AVCURTP = Adjusted Volume using the current test procedure. 

The VCAF, like the ESAF, is considered to be a function only of product class. 

Baseline energy use for the current test procedure is expressed as follows, where the 

constants A and B are a function of product class. 

BEC = A × AV + B Equation 5.4.3 CURTP CURTP 

Combining Equations 5.4.1 through 5.4.3 gives the following relationship for the 

baseline energy consumption based on the new test procedure. 

⎛ AVNEWTP ⎞ ⎛ ESAF ⎞ BEC = ESAF ×⎜ A × + B⎟ = ⎜ × A⎟× AV + (ESAF × B) NEWTP NEWTP ⎝ VCAF ⎠ ⎝VCAF ⎠

Hence, the baseline energy consumption for the product class for the new test 

procedure can be represented as a straight-line relationship based on new constants ANEW 

and BNEW, where the new constants are related to the current constants as follows. 

⎛ ESAF ⎞ ANEW = ⎜ ⎟ × A; BNEW = ESAF × B ⎝VCAF ⎠

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The baseline energy use based on the expected revised test procedure is presented 

in Table 5.4.10 below for each of the product classes. 

Table 5.4.10 New Baseline Energy Consumption based on Proposed Test Procedure 

Product 

Class 

1 

ESAF 

1.132 

VCAF 

1 

Current Baseline 

Energy Use 

(kWh/year) 

8.82 AV + 248.4 

Expected Test Procedure 

Baseline Energy Use 

(kWh/year) 

9.98 AV + 281.2 

1A 0.974 1.012 8.82 AV + 248.4 8.49 AV + 241.9 

2 1.132 1 8.82 AV + 248.4 9.98 AV + 281.2 

3 1.124 1.028 9.8 AV + 276 10.72 AV + 310.2 

3A 0.974 1.012 9.8 AV + 276 9.43 AV + 268.8 

4 1.14 1.016 4.91 AV + 507.5 5.51 AV + 578.6 

5 1.182 1.022 4.6 AV + 459 5.32 AV + 542.5 

5A 1.182 1.022 5 AV + 539 5.78 AV + 637.1 

6 1.124 1.028 10.2 AV + 356 11.15 AV + 400.1 

7 1.14 1.016 10.1 AV + 406 11.33 AV + 462.8 

8 1 1.017 7.55 AV + 258.3 7.42 AV + 258.3 

9 1 1.009 12.43 AV + 326.1 12.32 AV + 326.1 

10 1 1.017 9.88 AV + 143.7 9.71 AV + 143.7 

10A 1 1.009 14.76 AV + 211.5 14.63 AV + 211.5 

11 1.125 1 10.7 AV + 299 12.04 AV + 336.4 

11A 0.977 1 10.7 AV + 299 10.45 AV + 292.1 

12 1.125 1 7 AV + 398 7.88 AV + 447.8 

13 1.124 1.028 12.7 AV + 355 13.89 AV + 399.0 

13A 0.974 1.012 12.7 AV + 355 12.22 AV + 345.8 

14 1.14 1.016 7.6 AV + 501 8.53 AV + 571.1 

15 1.182 1.022 13.1 AV + 367 15.15 AV + 433.8 

16 1 1.017 9.78 AV + 250.8 9.61 AV + 250.8 

17 1 1.009 11.4 AV + 391 11.3 AV + 391 

18 1 1.017 10.45 AV + 152 10.27 AV + 152 

Note: In the “Current Baseline” equations, AV is calculated using the current volume calculation method 

and adjustment factor, while in the “Proposed” equations, AV is calculated using the proposed volume 

calculation method and adjustment factor (see Table 5.4.3) 

5.4.2.3 Investigation of the Slope of the Energy Use Curve 

DOE carried out analysis to confirm whether the slopes of the baseline energy 

use—adjusted volume curves for the product classes analyzed in depth as part of the 

engineering analysis are representative of the energy use of typical products. DOE 

conducted these analyses based on the expected revised test procedure. The analysis 

started with an energy model of a minimally-compliant product and examined the trend 

in calculated energy use as the product size changes with constant insulation thickness. 

For the analysis of compact refrigerators, DOE considered the change in efficiency of 

typically available compressors sized appropriately for the product. For standard-size 

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products the DOE used a constant compressor efficiency in the analysis, based on 

observation that compressor efficiency does not vary significantly in the capacity range 

suitable for most standard-size products (this is discussed in greater detail in section 

5.8.3). The energy—adjusted volume slopes calculated in this analysis are presented in 

Table 5.4.11 below. The table also shows the slopes of the proposed baseline energy 

use—adjusted volume relationships of Table 5.4.10 above. The comparison provides an 

indication of whether adjustment might be required to the proposed baseline energy use 

relationships, which are based on the current energy conservation standards and the 

expected impacts of the expected revised test procedure. The comparison shows that 

consideration may need to be given to whether the slope for the baseline energy use 

relationships should be adjusted for product classes 5, 11, 11A, and 18. By extension, 

similar consideration should be given to the slopes for product classes 4 and 5A, which 

were not directly examined, but the trends for which should be predicted by the analyses 

for product classes 7 and 5, respectively. The question of whether adjustments should be 

made to the baseline energy use relationships of Table 5.4.10 is a topic on which DOE 

requests comment from stakeholders. 

Table 5.4.11 DOE Assessment of the Slope of the Energy Use Curve 

Product Class 

Calculated 

Energy Curve Slope from 

ERA Models* 

Slope from Proposed 

Baseline Energy Use 

Equation (Table 5.4.10) 

3 13.3 10.7 

5 12.3 5.3 

7 11.9 11.3 

9 9.4 12.3 

10 7.7 9.7 

11 16.4 12.0 

11A 20 to 35** 10.5 

18 4.5 10.3 

* Analysis was conducted for both the small and large units analyzed for product classes 3, 5, 7, 

9, 10, 18. Values shown are averages of slopes for the two ERA models. 

** The energy use—adjusted volume relationship is nonlinear, with higher slope at lower 

volumes. The slopes indicated are applicable for a range of adjusted volumes from 1.7 to 3.6 ft3 

. 

5.4.3 Incremental Efficiency Levels 

DOE established a series of incremental efficiency levels, for which it has 

developed incremental cost data and quantified the cost-efficiency relationship for each 

of the seven analyzed product classes. The incremental efficiency levels are shown in 

Table 5.4.12 below. Maximum available efficiency levels for the analyzed product 

classes, which are based on a survey of product databases and manufacturer websites, are 

tabulated in Table 5.4.13 below. Maximum technology levels, which are based on DOE 

energy modeling using all applicable design options, are discussed in Section 5.4.4. 

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Table 5.4.12 Incremental Efficiency Levels (% Energy Use Less than Baseline) 

Level 

Standard-Size 

Refrigerator-Freezers 

(PC 3, 5, 7) 

Standard-Size 

Freezers 

(PC 9, 10) 

Compact Refrigerators 

and Freezers 

(PC 11, 18) 

1 10% 10% (Current 

ENERGY STAR) 10% 

2 15% (Former 

ENERGY STAR) 15% 15% 

3 20% (Current 

ENERGY STAR *) 20% 20% (Current ENERGY STAR *) 

4 25% (CEE Tier 2) 25% 25% (CEE Tier 2) 

5 30% (CEE Tier 3) 30% 30% (CEE Tier 3) 

6 35% 35% 35% 

7 40% 40% 40% 

8 45%** 45% 45% 

*Current ENERGY STAR is equivalent to CEE Tier 1 for standard-size refrigerators and refrigeratorfreezers and for all compact products. 

**The 45% efficiency level was not analyzed for product class 7 because it is beyond maximum 

technology according to DOE analysis. 

Table 5.4.13 Maximum Available Levels (%Energy Use Less than Baseline) 

Maximum Available Level** 

PC 

% Volume (ft3) Brand & Model # 

3 22% 18 Frigidaire FRT18HS7J 

5 26% 19 Sub-Zero BI30US8 

7 30% 26 Whirlpool GS5VHA 

9 43% 8 Gaggenau RF411700 

10 16% 9 W.C.Wood C09 

11 26% 6 MicroFridge 5.6MFR 

18 21% 5 Haier ESCM050 

** Source: ENERGY STAR Database (4/7/2009), CEE Database (3/16/2009), CEC Database (4/1/2009), 

Manufacturer websites 

5.4.4 Maximum Technology Level 

DOE defines a maximum technology level to represent the theoretical maximum 

possible efficiency if all available design options are incorporated. The maximum 

technology level is not to be confused with the maximum available level, which is the 

highest efficiency unit currently available on the market. In many cases the maximum 

technology level is not commercially available because it is not yet economically 

feasible. Figure 5.4.1 below shows the maximum available efficiency levels, based on the 

ENERGY STAR database of 4/9/09, with adjustments including deleting products which 

are no longer for sale based on the CEC database and manufacturers’ and retailers’ 

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websites. For this chart, the all-refrigerator products of product classes 1, 3, 11, and 13 

were not included—some of these have higher efficiency levels than those shown in the 

chart. The maximum available efficiency product varies significantly among the product 

classes, from 1% for product class 13 to 51% for product class 2. 

As mentioned, the maximum technology level may not represent available 

products because they may not be economically feasible. DOE determined maximum 

technology levels using energy modeling. The energy models for the maximum 

technology levels were based on use of all design options applicable for the specific 

product classes. While these product configurations have not likely been tested as 

prototypes, all of the individual design options have been incorporated in available 

products. The maximum technology efficiency levels for the analyzed product classes are 

presented in Table 5.4.14 below. These efficiency levels are significantly higher than the 

maximum available products. The costs of the maximum technology efficiency level 

designs are also quite high, being based on extensive use of high-cost design options such 

as vacuum insulating panels as well as all applicable lower-cost design options. Table 

5.4.14 indicates which design options were used for each of the product classes. 

Figure 5.4.1 Maximum Efficiency Levels Available by Product Class 

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Table 5.4.14 Maximum Technology Levels 

Design Options Used

Product Class% Lower Energy

Brushless DCEvaporator FanBrushless DCCon

denser Fan

Forced ConvectionCondenserLarger EvaporatorLarger CondenserThicker InsulationVIPsVariable SpeedCompressorAdaptive DefrostVariable AntiSweat 

3 56% 9 9 9 9 9 9 9

5 53% 9 9 9 9 9 9 9 9

7 45% 9 9 9 9 9 9 9

9 55% 9 9 9 9 9 9 9 9

10 51% 9 9 9 9 9

11 75% 9 9 9 9 9

18 52% 9 9 9

Note: Levels indicated are the average determined for the two products of each product 

class analyzed in detail. 

5.5 DATA COLLECTION 

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

The key sources include the following. 

• AHAM 

• Component Vendors 

• Reverse-Engineering of Products 

• Manufacturer Interviews 

• Energy Tests 

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

5.5.1 Manufacturer-Submitted Shipment and Cost Data from AHAM 

DOE included draft data requests sheets to support the engineering and other 

DOE analyses in the framework document as Tables A1 through A10 of that document. 

Some of these tables were revised based on comments received during the framework 

comment period. For example, incremental cost data was provided for up to 35% 

efficiency level, and included a 10% efficiency level, which replaced the 15% efficiency 

level of the draft tables. Other requests DOE made to AHAM in addition to the requests 

made in the framework document include the following. 

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•	 Historical shipment data for Wine Coolers, broken out by key types: manual 

defrost/auto defrost. 

•	 Historical shipment data for Built-in Refrigerators, disaggregated by product class. 

•	 Recent shipment data for products incorporating a wine cooler compartment with 

either (1) a fresh food compartment, (2) a freezer compartment, or (3) both a fresh 

food and a freezer compartment. 

•	 Recent shipment data for French Door refrigerators broken out between products with 

and without TTD ice service. 

•	 Recent shipment data for convertible-bottom-drawer refrigerators (products with 

three doors configured as a side-by-side arrangement on top with a single drawer 

below, and for which the upper compartments are freezer and fresh food 

compartments and the drawer is convertible). 

•	 Percent of refrigerator-freezers shipped with ice makers for applicable product classes 

(3, 4, 5, 13, 14, 15), historical data if possible. 

•	 Total shipments of ice makers (any breakdown by (a) installed at factory, (b) installed 

by dealer, (c) installed by homeowner?), historical data if possible. 

•	 For as many refrigerator, refrigerator-freezer, and freezer models as practical, data on 

the impact of the proposed changes in compartment temperature and volume 

calculation method: 

o	 Compartment Volumes: volumes calculated according to the current 

procedure and according to the new procedure, with indication of product 

class. 

o	 Energy use (for refrigerators and refrigerator-freezers only): Annual energy 

use measurements for units tested for both temperatures (i.e. not Energy Label 

data—this should be energy test values calculated based on test data for the 

old temperatures and the new temperatures for sequential tests of the same 

unit. This will typically require three tests to make sure that both sets of 

temperatures are bracketed. 

o	 It is anticipated that data for product classes 3 and 13 would be separated 

according to whether the product is a refrigerator-freezer or all-refrigerator. 

AHAM supported the rulemaking by supplying much of this data. AHAM 

supplied DOE with aggregated shipment-weighted average data for many of the 

submittals in order to avoid divulging data submitted by individual manufacturers. The 

AHAM incremental cost data included incremental material, labor, and overhead costs as 

well as conversion capital expenditures and one-time product conversion expenses for 

each efficiency level. These data are presented in Section 5.9.2, where they can more 

readily be compared with the results of DOE analysis. Data associated with other AHAM 

submittals are presented in the relevant chapters and sections most directly related to the 

data in question. 

5.5.2 Component Vendor Data 

DOE directly contacted major suppliers of key refrigerator and freezer 

components to obtain performance and cost data to support its design option analysis. 

The data received from vendors was compared with information received from 

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manufacturers during the manufacturer interviews in order to develop input values for 

performance and cost parameters for the energy modeling and manufacturing cost 

modeling. This vendor solicitation effort consisted of phone interviews, email 

correspondence, and in-person interviews. Table 5.5.1 lists the vendors contacted. 

DOE also obtained from the compressor vendors or their websites complete 

performance data for compressors used in many of the energy analyses, including 

analyses for baseline and improved-efficiency configurations. 

Table 5.5.1 Component Vendors Contacted by DOE during Engineering Analysis 

Component Type Vendors 

Compressors Embraco 

Tecumseh 

Matsushita 

Danfoss 

LG 

Huayi 

ACC (ZEL) 

Jiangsu Baixue Electric Appliances Co.,Ltd 

Fan Motors Matsushita 

VIPs va-Q-tec 

Matsushita 

Foam Insulation BASF 

Foam Supplies 

Heat Exchangers Brazeway 

5.5.3 Reverse Engineering 

DOE purchased a number of representative refrigerators and freezers as part of 

the engineering analysis in order to examine design and fabrication details. This reverseengineering included detailed measurement of dimensions, system and component-level 

power measurements, measurement of air flows for products with forced convection heat 

exchangers, and physical teardowns. The results of the reverse engineering process were 

used as input to the manufacturing cost modeling and the energy use modeling. This 

section describes the selection of products for reverse-engineering as well as some of the 

measurements made to support subsequent modeling. Section 5.6 provides a more 

thorough description of the physical teardown process used to support manufacturing cost 

modeling. 

5.5.3.1 Selection of Products for Reverse Engineering 

DOE performed reverse engineering on units rated at baseline and improved (i.e., 

ENERGY STAR) energy consumption levels for the seven analyzed product classes. 

DOE chose at least one representative small-size and one large-size unit to cover the 

range of volumes within each product class. In order to best examine the design choices 

associated with efficiency improvements, DOE selected baseline efficiency/ENERGY 

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STAR product pairs if possible, for which the two products were identical other than the 

differences necessary for the ENERGY STAR-rated product to achieve higher efficiency. 

Such product pairs included the 21 ft3

 Top-Mount refrigerator-freezers, the 26 ft3 SideMount refrigerator-freezers, the 20 ft3 upright freezers, and the 4 ft3 compact refrigerators. 

Table 5.5.2 lists descriptions of the selected units and indicates whether energy testing 

was performed (see Section 5.5.5 for more on energy testing). 

Table 5.5.2 Selected Units for Reverse-Engineering and Energy Testing 

PC Product Description 

Energy % 

Less than 

Baseline 

Energy 

Test 

Physical 

Teardown 

Energy Use 

Model 

16 ft3 Top-Mount R-F 0% 9 9 9

21 ft3 3 Top-Mount R-F 0% 9 9 9

21 ft3

 E* Top-Mount R-F 20% 9 9 9

4 22 ft3 Side-Mount R-F† 0% 9 9 9

18.5 ft3 E* Bottom-Mount R-F 15%* 9 9 9

25 ft3 5 E* Bottom-Mount R-F 1 20% 9 9

25 ft3 E* Bottom-Mount R-F 2 20% 9 9

25 ft3 French Door E* BottomMount R-F 20% 

9

5A 26 ft3

 French Door E* BottomMount R-F 20% 

26 ft3 Side-Mount R-F 0% 9 9 9

7 26 ft3

 E* Side-Mount R-F 20% 9 9 9

14 ft3 Upright Freezer 0% 9 9

20 ft3 Upright Freezer 2% 9 9 9

20 ft3 E* Upright Freezer 1 12% 9 9 9 

20 ft3 E* Upright Freezer 2 10% 

15 ft3 Chest Freezer 1% 9 9 9

15 ft3 10 E* Chest Freezer 11% 9 9

20 ft3

 Chest Freezer 0% 9 9

1.7 ft3 Compact Refrigerator 7% 9 9 9

4 ft3 11 Compact Refrigerator 2% 9 9

4 ft3 E* Compact Refrigerator 22% 9 9

3.4 ft3 Compact Chest Freezer 0% 9 9

7 ft3 18 Compact Chest Freezer 1 1% 9 9

7 ft3

 Compact Chest Freezer 2 1% 9 9

*Exact efficiency level is not known because product literature did not include indication 

of separate compartment volumes. 

†This product was thought to be product class 7 when purchased. 

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5.5.3.2 Collection of Energy Modeling Data 

DOE examined each unit prior to teardown to record details to be used as input 

for the energy modeling. The key measurements are described in this section. 

The rated refrigerated volumes for each product’s compartments and its rated 

energy use were based on product literature or the ENERGY GUIDE. In the case of the 

3.4 ft3

 chest freezer, the product literature did not provide an indication of energy use, 

and the product did not arrive with an ENERGY GUIDE. For this product, DOE assumed 

that energy use was exactly equal to maximum allowable energy use for the product 

class. 

Power input for the product was measured for a period of 24 or more hours. This 

measurement was not intended to be an energy test, but provided useful information 

regarding the product controls, including off-cycle wattage, defrost heater on-time, and 

defrost interval (or indication of variable defrost). The power measurements for the 

products were made in the reverse engineering test laboratory, whose ambient 

temperature may have covered a broad range from 65  ̊F to 85  ̊F during the time that 

these measurements were carried out. Also, careful attention was not paid to the 

temperature setpoints for this measurement—the setpoints generally were left in the asshipped positions. 

Component-level power measurements were carried out for fans, defrost heaters, 

and manual defrost controls for the products which had these components. Power was 

also measured for some products’ anti-sweat heaters. 

Air flow measurements were made for all forced-convection heat exchangers. 

These measurements were made with 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 reliable, so this 

measurement was used as an indication of air flow trends more than exact indication of 

air flow for the various products. 

Details of the cabinet size and insulation thickness were based on direct physical 

measurements. Most of these measurements were made prior to the teardown, but 

measurements of some parameters, such as outer shell thickness, inner liner thickness, 

and insulation thickness, were made during the teardown process. Use of insulation other 

than polyurethane foam was noted as part of the teardown process. Frame area details 

including gasket details were observed, and recorded with pictures as part of the 

teardown process. 

Heat exchanger details were recorded, including type, configuration, numbers of 

tubes and fins, dimensions, etc. For cold wall and hot wall heat exchangers this data was 

recorded during the product teardown process. The details of anti-sweat heaters were also 

determined during the teardown process, including the layout for refrigerant anti-sweat 

loops. The details of suction line heat exchangers were similarly determined during 

teardown. 

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Component manufacturer and model data were recorded for key components such 

as compressors, fans, and controls. 

The energy modeling data for the teardown products are presented in detail in 

appendix 5-A. 

5.5.4 Manufacturer Interviews 

DOE’s contractor discussed engineering issues with manufacturers during the preNOPR interviews. The engineering questions were consolidated into an engineering 

questionnaire, which guided the interview process for all of these discussions. The 

engineering questionnaire is shown in appendix 5-A. Key technical topics addressed 

during these discussions include the following: 

•	 Typical characteristics of components and typical design details (i.e. such as 

insulation thicknesses) used for key product classes. 

•	 Typical design differences between baseline and ENERGY STAR products. 

•	 Differences in design pathways and incremental costs across different product classes 

•	 Viability of technology options, and their typical costs. 

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

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. 

5.5.5 Energy testing 

DOE conducted energy testing to verify energy use of many of the products 

obtained for reverse engineering, to provide refrigeration system data to support energy 

use modeling, and to evaluate the difference in energy use between current energy test 

compartment temperatures and the new temperatures associated with the expected revised 

test procedure. 

Twelve of the 24 units were tested, as indicated in Table 5.5.2, including all of the 

refrigerator-freezer models and one each of the upright freezers, chest freezers, and 

compact refrigerators. No compact chest freezers were tested. 

Energy testing was carried out by an independent test lab according to the DOE 

Energy Test Procedure as described in 10 CFR Part 430 Subpart B, Appendix A1 or B1, 

with reference to AHAM Standard HRF-1-1979 as applicable. In addition to the standard 

energy test results, DOE requested specific temperature measurements to be taken 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, insulated externally from local ambient air. 

Table 5.5.3 lists the additional measurements. 

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Table 5.5.3 Additional Thermocouple Locations for Energy Test 

Thermocouple Location RefrigeratorFreezers 

Upright 

Freezer 

Chest 

Freezer 

Compact 

Refrigerator 

Discharge 4” from shell 9 9 9 9

Condenser Inlet 9

Condenser Mid 9

Condenser Outlet 9 9 9 9

Evaporator Inlet 9 9 9

Evaporator Outlet 9 9 9 9

Suction 4” from shell 9 9 9 9

Condenser Air Inlet 9

Pan Heater In 9

Pan Heater Out 9

Hot Wall Condenser 

Surface 

9 9 9

Compressor 

Compartment Air 

9 9 9

Cold Wall Evaporator 

Surface 

9 9

Two units of the 1.7 ft3

 compact refrigerator were tested because the first of these 

was not able to hold proper internal temperatures. 

5.6 MANUFACTURING COST MODELING 

5.6.1 Generation of Bills of Materials 

The end result of each teardown is a structured bill of materials (BOM). DOE 

developed structured BOMs for each of the physical teardowns. Structured BOMs 

describe each product part and its relationship to the other parts in the estimated order in 

which manufacturers assembled them. The BOMs describe each fabrication and assembly 

operation in detail, including the type of equipment needed (e.g., presses, drills), the 

process cycle times, and the labor associated with each manufacturing step. The result is 

a thorough and explicit model of the production process, which includes space, conveyor, 

and equipment requirements by planned production level. 

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

either raw materials or purchased parts and assemblies. The classifications into raw 

materials or purchased parts were based on DOE’s previous industry experience, recent 

information in trade publications, and discussions with high- and low-volume original 

equipment manufacturers (OEMs). DOE also visited manufacturing plants to reinforce its 

understanding of the industry’s current manufacturing practices for each of the three 

product categories. 

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

price quotations and detailed discussions with manufacturers and component suppliers. 

For fabricated parts, the prices of “raw” materials (e.g., tube, sheet metal) are estimated 

on the basis of 5-year averages (see Section 5.6.4.4). The cost of transforming the 

intermediate materials into finished parts is estimated based on current industry pricing. 

DOE shared major estimates with manufacturers during the engineering manufacturer 

interviews to gain feedback on the analysis, its methodology, and preliminary results. 

5.6.2 Cost Structure of the Spreadsheet Models 

The manufacturing cost assessment methodology used is a detailed, componentfocused technique for calculating the manufacturing cost of a product (direct materials, 

direct labor, and the overhead costs associated with production). 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, dimensions, 

material, and quantity. The BOM incorporates all materials, components, and fasters 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. Interview and plant visits were 

conducted with manufacturers to add industry experience on the 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. Although most of the assumptions 

are manufacturer specific and cannot be revealed, Section 5.6.4.3 provides a discussion of 

the values used for each assumption. 

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., door assembly, heat exchanger assembly, shelving, packaging, 

controls, bottom components assembly, wiring harnesses, inner/outer wrapper assembly, 

etc.) and summarized these costs in a worksheet. During engineering interviews with 

manufacturers, DOE showed key estimates from the cost model and asked for feedback. 

DOE considered any information manufacturers gave that was relevant to the cost model 

and incorporated it into the analysis, if appropriate. 

5.6.3 Cost Model and Definitions 

Once DOE disassembled selected units, gathered information from manufacturer 

catalogs on additional products, and identified technologies, DOE created an appropriate 

manufacturing cost model that could translate physical information into manufacturer 

production costs (MPCs). The cost model is based on production activities and divides 

factory costs into the following categories: 

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•	 Materials: Purchased parts (i.e. compressor, fan motors, control boards, door handles, 

shelf frames, 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. 

5.6.3.1 Cost Definitions 

Because there are many different accounting systems and methods to monitor 

costs, DOE defined the above terms as follows: 

•	 Direct material: Purchased parts (out-sourced) plus manufactured parts (made inhouse from raw materials). 

•	 Indirect material: Material used during manufacturing (e.g., welding rods, adhesives). 

•	 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 wears out. 

•	 Tooling depreciation: Cost for initial tooling (including nonrecurring engineering and 

debugging of the tools) and tooling replacement as it wears out. 

•	 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 as unit cost. 

5.6.4 Cost Model Assumptions Overview 

As discussed in the previous section, assumptions about manufacturer practices 

and cost structure played an important role in estimating the final product cost. Some 

assumptions were different for specific manufacturers, depending on their market 

position, manufacturing practices, and size. 

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 

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EERE-2008-BT-STD-0012 COMMENT 20
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 included assembly, fabrication, supervisor, and indirect labor. 

Overhead costs included equipment depreciation, tooling depreciation, building 

depreciation, utilities, equipment, tooling maintenance, insurance, property, and taxes. 

DOE used the information gathered from manufacturer interviews to make 

updates to the cost model. These changes involved updating component and material 

pricing. 

The next sections discuss specific assumptions about outsourcing, factory 

parameters, production volumes, and material prices. When the assumptions are 

manufacturer-specific, they are presented as industry averages to prevent disclosure of 

confidential information. 

5.6.4.1 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. 

DOE based the manufacturing operations assumptions on internal expertise, 

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

manufacturer processes identified and developed for the spreadsheet model are listed in 

Table 5.6.1. Fabrication process cycle times were estimated and entered into the BOM. 

Table 5.6.1 Cost Model In-House Manufacturing Operation Assumptions 

Fabrication Finishing Assembly/Joining Quality Control 

Fixturing 

Stamping/Pressing 

Turret Punch 

Tube Forming 

Brake Forming 

Cutting & Shearing 

Insulating & 

Insulation Injection 

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 

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5.6.4.2 Production Volumes Assumptions 

A manufacturer’s production volumes vary depending on several factors, 

including market share, the type of product produced (i.e., standard- size refrigeratorfreezer, compact refrigerator-freezer, etc.), and if the manufacturer produces other similar 

products. DOE based production volume assumptions for these residential refrigeration 

products on shipment data, industry knowledge, and engineering manufacturer 

interviews. The manufacturing plant annual production capacities used for the analyses 

differ by product class as follows. 

• Product Classes 3 and 6: 1.5 million 

• Product Classes 5 and 5A: 0.5 million 

• Product Classes 4 and 7: 1 million 

• Product Class 9: 150,000 

• Product Class 10: 100,000 

• Product Class 11: 0.5 million 

• Product Class 18: 100,000 

5.6.4.3 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 5.6.2 

lists DOE’s assumptions for refrigerator manufacturers. 

Table 5.6.2 Refrigerator & Freezer Factory Parameter Assumptions 

Parameter Assumption 

Plant Capacity (units/yr) see section 5.6.4.2 

Actual Annual Production Volume (units/yr) 5/6 of plant capacity 

Fabrication Labor Wages ($/hr) 16.00 

Fringe Benefits Ratio 50% 

5.6.4.4 Material Cost Assumptions 

DOE determined the cost of raw materials using publicly available information 

such as the American Metals Marketa

, interviews with manufacturers, and direct 

discussions with material suppliers. Common metals used in the fabrication of residential 

refrigerator products include plain cold rolled steel (CRS), 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 

a

 American Metals Market. Last accessed November 2008. <http://www.amm.com>. 

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Statistics Producer Price Indices (PPIs) spanning 2003 to 2008 with an adjustment to 

2008$.b

 DOE used the PPIs for copper rolling, drawing, and extruding and steel mill 

products, and made the adjustments to 2008$ using the gross domestic product implicit 

price deflator.c

 Table 5.6.3 shows the 5-year average metal prices DOE used for the 

analysis. 

Table 5.6.3 Five-Year Metal Prices (2003-2008) 

Metals Cost ($/lb) ($2008) 

Plain Cold Rolled Steel (CRS) $0.36 

Painted CRS $0.57 

Galvanized CRS $0.48 

Aluminized CRS $0.54 

Textured CRS $0.61 

CRS Tube $0.74 

Stainless Steel $2.06 

Fin Aluminum $1.64 

Plain Copper $2.13 

Copper Tube – Plain $2.76 

Brass $1.45 

Galvanized Wire $0.60 

Standard Aluminum $1.26 

Copper Tube – Rifled $2.96 

Aluminum Tube $1.89 

Hot Rolled Steel $0.37 

Hot Rolled Steel Pipe $0.47 

Between 2003 and 2006, the price of steel rose over 60 percent and the price of 

copper rose over 140 percent. DOE used a 5-year average in material prices from 2003 to 

2008 to normalize these drastic increases to better represent long-term material price 

averages. 

For resins used in the fabrication of these refrigeration products, DOE used 

current resin prices gathered from industry research, publications such as Plastics News,d 

and interviews with manufacturers. Resin prices are determined by quantity and supplier 

(i.e., contract specific) and therefore have no true fixed market price. For this analysis, 

DOE used market resin prices current as of November 2008. The prices of resins have 

been constantly increasing and closely follow petroleum prices. Table 5.6.4 shows the 

current resin prices used in the analysis. 

b

 U.S. Department of Labor, Bureau of Labor Statistics, Producer Price Indices. Last accessed November 

2008. <http://www.bls.gov/ppi>. 

c

 U.S. Department of Commerce, Bureau Economic Analysis, Gross Domestic Product Implicit Price 

Deflator. Last accessed November 2008. <https://bea.gov/bea/dn/nipaweb/TableView.asp#Mid>. d Plastic News, Resin Pricing. Last accessed March 21, 2008. 

<http://www.plasticsnews.com/subscriber/headlines.phtml>. 

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‐  

   

   

   

   

   

   

   

     

   

   

   

 

Table 5.6.4 Most Prevalent Resin Prices as of December 2007 

Resins Cost ($/lb) ($2008) 

Polystyrene (PS) $0.66 

Polypropylene (PP) $0.67 

Low Density Polyethylene $0.73 

Polyurethane Foam (non-HCFC blowing agent) $1.29 

PVC (Hard) $0.47 

5.6.5 Manufacturing Production Cost 

Once the cost estimate for each teardown unit was finalized, a detailed summary 

was prepared 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.e

 Figure 5.6.1 shows the general breakdown of costs associated with 

manufacturing a product. 

Manufacturer

Selling Price

Full Cost of

Product Profit

Manufacturer

Production Cost

Direct

Labor

Direct

Material Overhead

Indirect Labor

Indirect Material

Maintenance

Depreciation

Taxes

Insurance related

to assets

Figure 5.6.1 Full Production Costs 

e 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 (COGS). 

Non Production

Cost

Selling

Market

Research

Advertising

POS Promotion

Salesperson

Comp & Travel

Logistics

(Warehousing,

Delivery, Record‐

Keeping, Order

Processing)

General &

Admin.

Costs of

Service &

Staff Units

General

Corporate

Costs

(Comp, etc)

R & D

Costs associated

with finding new

and improved

products or

processes

Code

Compliance

Modernization

Interest

Cost of

borrowing

funds

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EERE-2008-BT-STD-0012 COMMENT 20
The full cost of product is broken down into two main costs, the full production 

cost or MPC, and the non-production cost. The non-production cost is equal to the 

manufacturer markup minus profits. 

Technologies used in the units subject to teardown are noted in the summary sheet 

of each cost model and are cost-estimated individually. Thus, various implementations of 

technologies can be accommodated, ranging from assemblies that are entirely purchased 

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

parts and parts made on site are thus also accommodated. 

5.6.6 Incremental Cost Estimates 

Incremental costs were determined for design options applied to the baselineefficiency refrigerator models. The approach for estimating the incremental costs varied 

depending on the design option. Details in this calculation which are specific to 

individual design options are discussed in Section 5.8, which discusses design options. 

Aspects of the incremental cost calculation which 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 

higher-efficiency component. For these design options, the increased price paid by the 

OEM for the new component represents the manufacturing cost increase—other elements 

of product cost such as overhead and capital expenditures would be insignificantly 

affected by these design changes. The appropriate 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. The baseline manufacturing cost was subtracted from the manufacturing cost of the 

modified design to determine the incremental cost of the design option. This approach 

was used in particular for insulation thickness increases and heat exchanger size increases 

for cold wall and hot wall heat exchangers. 

5.6.6.1 Overhead and Depreciation Costs 

Some design options involve costs in addition to the price increase associated 

with a new component. For such options, there may be overhead and capital expenses 

which must be added to the direct costs associated with the design option. Estimates of 

typical additional costs associated with overhead and depreciation for manufacture of 

refrigeration products were made for the reverse-engineering models, using estimates of 

these costs provided by the manufacturing cost model. These calculations were carried 

out based on proposed typical production plant capacities, with actual production 

volumes estimated to be 5/6 of plant capacities. The annual plant capacities for the 

product classes used in these calculations are as indicated in section 5.6.4.2. 

The additional costs are presented as percentage of direct material and labor costs 

in Table 5.6.5 below. The averages for the listed product class categories were used to 

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increase direct material and labor costs for some design options for which this adjustment 

was necessary. 

Table 5.6.5 Overhead and Depreciation Cost Ratios 

Product Class Product Product Percent Average Percent 

Group Class Cost Cost Ratio for 

Ratio Product Class 

Group 

Standard- 16 ft3

 Top-Mount R-F 31.2% 

23.4% 

Size 3 21 ft3

 Top-Mount R-F 23.2% 

Refrigerator- 21 ft3

 E* Top-Mount R-F 23.2% 

Freezers 4 22 ft3

 Side-Mount R-F† 22.0% 

19 ft3

 E* Bottom-Mount R-F 23.5% 

5 25 ft3

 E* Bottom-Mount R-F 1 20.9% 

25 ft3

 E* Bottom-Mount R-F 2 23.3% 

7 26 ft3

 Side-Mount R-F 20.7% 

26 ft3 E* Side-Mount R-F 22.5% 

Standard- 14 ft3 Upright Freezer 28.6% 

28.5% 

Size Freezers 9 20 ft3

 Upright Freezer 26.2% 

20 ft3 E* Upright Freezer 1 25.0% 

15 ft3 Chest Freezer 35.5% 

10 15 ft3

 E* Chest Freezer 33.2% 

20 ft3 Chest Freezer 22.5% 

Compact 1.7 ft3 Compact Refrigerator 40.2% 

39.2% 

Refrigerators, 11 4 ft3

 Compact Refrigerator 35.6% 

RefrigeratorFreezers, and 

Freezers 

4 ft3 E* Compact Refrigerator 36.5% 

18 

3.4 ft3 Compact Chest Freezer 42.3% 

7 ft3

 Compact Chest Freezer 1 36.6% 

7 ft3

 Compact Chest Freezer 2 44.2% 

The manufacturing cost model estimates are consistent with overall industry 

trends. Census data shows that the average value of this cost adder for NAICS code 

335222 (Household Refrigerator and Home Freezer Manufacturing) is 27.7%. 

5.6.6.2 Depreciation Costs for Insulation Thickness Increases 

DOE considered that increases in cabinet wall and door thicknesses would require 

redesign of the entire refrigerator or freezer platform and lead to building of a new 

production plant. This conservative approach to the analysis was based on input from 

manufacturers. For such design changes, the difference in greenfield costsf

 of two designs 

would not capture the depreciation costs which would be incurred by the manufacturer 

and which would add to the product cost after such a platform conversion. DOE 

conservatively used the greenfield depreciation costs per product determined by the 

f

 Greenfield costs are defined as the costs associated with building a new manufacturing facility, to be 

distinguished from the costs required to upgrade or modify a facility. 

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manufacturing cost model as an additional cost for wall thickness increases. The 

calculation of manufacturing costs for all of the teardown products based on typical plant 

capacities described above was used as the basis for the determination of greenfield 

depreciation costs per product. The results of the calculations are summarized in Table 

5.6.6 below. Average depreciation costs were applied in the engineering analyses for 

product class groups with similar levels of depreciation costs, as indicated in the table. 

Table 5.6.6 Greenfield Depreciation Costs per Product 

Product Product Product Depreciation Average 

Class Group Class Cost Depreciation 

Cost for 

Product Class 

Group 

StandardSize 

RefrigeratorFreezers 

3 

16 ft3

 Top-Mount R-F $29.60 $27.05 

21 ft3 Top-Mount R-F $23.55 

21 ft3

 E* Top-Mount R-F $23.97 

4 22 ft3

 Side-Mount R-F† $28.95 

19 ft3

 E* Bottom-Mount R-F $27.49 

5 25 ft3

 E* Bottom-Mount R-F 1 $27.95 

25 ft3

 E* Bottom-Mount R-F 2 $39.57 

7 26 ft3

 Side-Mount R-F $26.74 

26 ft3 E* Side-Mount R-F $28.14 

Freezers 

9 

14 ft3 Upright Freezer $19.08 $18.26 

20 ft3 Upright Freezer $18.21 

20 ft3

 E* Upright Freezer 1 $18.41 

15 ft3

 Chest Freezer $18.54 

10 15 ft3

 E* Chest Freezer $19.59 

20 ft3 Chest Freezer $17.31 

18 

3.4 ft3 Compact Chest Freezer $21.00 

7 ft3

 Compact Chest Freezer 1 $16.91 

7 ft3 Compact Chest Freezer 2 $15.32 

Compact 

Refrigerators 11 

1.7 ft3

 Compact Refrigerator $8.35 $8.98 

4 ft3

 Compact Refrigerator $9.29 

4 ft3

 E* Compact Refrigerator $9.29 

5.6.6.3 G&A and Profit 

DOE estimated the further addition to the manufacturer selling price associated 

with G&A and profit for the appliance industry as 26% of manufacturer production cost. 

This adder was applied to all of the MPC estimates in order to determine manufacturer 

selling price (MSP) numbers. This markup is described in more detail in chapter 6. 

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