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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 EFFICIENCY LEVELS................................................................................................... 5-2

5.3.1 Baseline Units.................................................................................................................. 5-3

5.3.2 Incremental Efficiency Levels......................................................................................... 5-3

5.3.2.1 Standard Product Class.................................................................................. 5-3

5.3.2.2 Compact Product Class.................................................................................. 5-4

5.4 METHODOLOGY OVERVIEW.................................................................................... 5-5

5.4.1 AHAM Data Request....................................................................................................... 5-5

5.4.2 Manufacturer Interviews.................................................................................................. 5-5

5.4.3 Product Teardowns .......................................................................................................... 5-6

5.4.3.1 Selection of Units........................................................................................... 5-6

5.4.3.2 Generation of Bill of Materials...................................................................... 5-6

5.4.3.3 Cost Structure of the Spreadsheet Models..................................................... 5-7

5.4.3.4 Cost Model and Definitions........................................................................... 5-8

5.4.3.5 Cost Model Assumptions............................................................................... 5-9

5.4.4 Review of Previous Technical Support Documents and Models..................................... 5-9

5.4.5 Product Testing .............................................................................................................. 5-10

5.5 ANALYSIS AND RESULTS........................................................................................ 5-10

5.5.1 AHAM Data................................................................................................................... 5-10

5.5.2 Product Teardowns ........................................................................................................ 5-11

5.5.2.1 Baseline Construction: Standard Dishwasher.............................................. 5-12

5.5.2.2 Baseline Construction: Compact Dishwasher.............................................. 5-14

5.5.2.3 Construction at Higher Efficiency Levels.................................................... 5-15

5.5.3 Cost-Efficiency Curves.................................................................................................. 5-21

5.5.3.1 Standard Dishwashers.................................................................................. 5-21

5.5.3.2 Compact Dishwashers.................................................................................. 5-21

5.5.4 Manufacturer Interviews................................................................................................ 5-22

5.5.4.1 Design Features of Current Baseline Products ............................................ 5-23

5.5.4.2 Proposed Incremental Efficiency Levels..................................................... 5-23

5.5.4.3 Design Options Required to Meet Each Efficiency Level........................... 5-23

5.5.4.4 Impact on Consumer Utility......................................................................... 5-23

5.5.4.1 Installation and Repair Costs as a Function of Efficiency........................... 5-24

LIST OF TABLES

Table 5.3.1 Standard Dishwasher Efficiency Levels, Based on Annual Energy Use and

Water Consumption ............................................................................................. 5-4

Table 5.3.2 Efficiency Levels for Compact Residential Dishwashers......................................... 5-5
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Table 5.4.1 Major Manufacturing Processes ............................................................................... 5-8

Table 5.5.1 AHAM Residential Dishwasher Shipments Data Submittal .................................. 5-10

Table 5.5.2 AHAM Residential Dishwasher Shipment-Weighted Average Efficiency 

Data Submittal ................................................................................................... 5-11

Table 5.5.3 AHAM Residential Dishwasher Market Share Efficiency Data Submittal............ 5-11

Table 5.5.4 Standard Residential Dishwasher Features............................................................. 5-12

Table 5.5.5 Baseline Standard Dishwasher Production Cost Distribution ................................ 5-13

Table 5.5.6 Baseline Standard Dishwasher Materials Cost Distribution................................... 5-14

Table 5.5.7 Baseline Compact Dishwasher Production Cost Distribution ................................ 5-15

Table 5.5.8 Baseline Compact Dishwasher Materials Cost Distribution................................... 5-15

Table 5.5.9 Standard Dishwasher Incremental Manufacturing Costs........................................ 5-21

Table 5.5.10 Compact Dishwasher Incremental Manufacturing Costs ..................................... 5-22

LIST OF FIGURES

Figure 5.4.1 Manufacturing Cost Assessment Stages.................................................................. 5-7

Figure 5.5.1 Baseline Standard Dishwasher Production Cost Distribution............................... 5-13

Figure 5.5.2 Baseline Standard Dishwasher Materials Cost Distribution ................................. 5-14

Figure 5.5.3 Baseline Compact Dishwasher Production Cost Distribution............................... 5-15

Figure 5.5.4 Baseline Compact Dishwasher Materials Cost Distribution ................................. 5-15
5-1

CHAPTER 5. ENGINEERING ANALYSIS

5.1 INTRODUCTION

After conducting the screening analysis, the U.S. Department of Energy (DOE) 

performed an engineering analysis based on the remaining design options. The engineering 

analysis consists of estimating the energy and water consumption and costs of residential

dishwashers at various levels of increased efficiency. This section provides an overview of the 

engineering analysis (section 5.1), discusses product classes (section 5.2), establishes baseline 

and incremental efficiency levels (section 5.3), explains the methodology used during data 

gathering (section 5.4) and discusses the analysis and results (section 5.5).

The primary inputs to the engineering analysis are baseline information from the market 

and technology assessment (chapter 3 of this direct final rule technical support document (TSD)) 

and technology options from the screening analysis (chapter 4). Additional inputs include cost 

and energy efficiency data, which DOE received from the Association of Home Appliance 

Manufacturers (AHAM) and qualified and supplemented through teardown analysis and 

manufacturer interviews. The primary output of the engineering analysis is a set of costefficiency curves. In the subsequent markups analysis (chapter 6), DOE determined customer 

(i.e. product purchaser) prices by applying distribution markups, sales tax and contractor 

markups. After applying these markups, the cost-efficiency curves serve as the input to the 

building energy-use and end-use load characterization (chapter 7), and the life-cycle cost (LCC) 

and payback period (PBP) analyses (chapter 8). 

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

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

specific design options to a baseline model; (2) the efficiency-level approach, which calculates 

the relative costs of achieving increases in energy efficiency levels, without regard to the 

particular design options used to achieve such increases; and/or (3) the reverse-engineering or 

cost-assessment approach, which involves a “bottom-up” manufacturing cost assessment based 

on a detailed bill of materials (BOM) derived from teardowns of the product or equipment being 

analyzed. Deciding which methodology to use for the engineering analysis depends on the 

covered product, the design options under study, and any historical data that DOE can draw on. 

5.2 PRODUCT CLASSES ANALYZED

DOE separated residential dishwashers into two product classes. In general, the criteria 

for separation into different classes are (1) type of energy used (natural gas or electricity), and 

(2) capacity or other performance-related features such as those that provide utility to the 
5-2

consumer, or others deemed appropriate by the Secretary that would justify the establishment of 

a separate energy conservation standard. (42 U.S.C. 6295 (q))

For dishwashers, the size of the unit significantly impacts the energy consumed. In other 

words, standard-size dishwashers with relatively greater water consumption have significantly 

greater energy use than compact units. Because standard dishwashers offer enhanced consumer 

utility over compact units (i.e., the ability to wash more dishes), DOE has separated residential 

dishwashers into the following two product classes, based on the size of the dishwasher (as 

specified in American National Standards Institute (ANSI)/AHAM Standard DW-1-1992, 

Dishwashers):

 Compact, capacity less than 8 place settings plus 6 serving pieces; and

 Standard, capacity equal to or greater than 8 place settings plus 6 serving pieces.

For this engineering analysis, DOE analyzed products from both the standard and 

compact product classes.

5.3 EFFICIENCY LEVELS

For residential dishwashers, energy conservation standard levels are currently defined by 

two factors –annual energy use and water consumption. The annual energy use calculation 

accounts for machine electrical energy consumption, external water heating energy consumption, 

and standby energy consumption. Water consumption is a direct measurement of the water used 

during the energy test for non-soil-sensing dishwashers, and a weighted average of the water 

used for the three different test cycles (with heavy, medium, and light soil loads) for soil-sensing 

dishwashers.

Section 310 of the Energy Independence and Security Act of 2007 (EISA 2007), Pub. L. 

110-140, amended section 325 of the Energy Policy and Conservation Act (EPCA) of 1975, Pub. 

L. 94-163, (42 U.S.C. 6291–6309) to require that the test procedure for dishwashers be amended 

to include measurement of standby mode and off mode energy use, taking into consideration the 

most current versions of Standards 62301 and 62087 of the International Electrotechnical

Commission (IEC).a

 EPCA, as amended by EISA 2007, also required that any final rule 

establishing or revising a standard for a covered product, adopted after July 1, 2010, shall 

incorporate standby mode and off mode energy use into a single amended or new standard, if

feasible. If not feasible, the Secretary shall prescribe within the final rule a separate standard for 

standby mode and off mode energy consumption. (42 U.S.C. 6295(gg))

 

a The most current version is IEC Standard 62301, “Household electrical appliances–Measurement of standby 

power”, Second Edition, 2011. IEC Standard 62087, “Methods of measurement for the power consumption of audio, 

video, and related equipment,” Second Edition, 2008-2010, is not applicable to this rulemaking. IEC standards may 

be purchased online at www.iec.ch.
5-3

The current DOE dishwasher test procedure in 10 CFR 430, subpart B, appendix C 

already includes a measure of standby mode energy use, although it is not based on the methods 

in IEC Standard 62301. DOE is conducting a rulemaking to amend the test procedure for 

dishwashers to provide for measurement of standby mode and off mode energy use based on IEC 

Standard 62301. DOE does not expect, however, that the amended test procedure will result in 

significantly different measured annual energy uses for residential dishwashers. As a result, 

DOE believes that the analyses described in the direct final rule TSD using efficiency ratings 

based on the existing test procedure will remain valid after the test procedure amendments take 

effect.

5.3.1 Baseline Units

DOE selected a baseline unit to represent the basic characteristics of equipment for 

dishwashers. Typically, a baseline unit is a unit that just meets current energy conservation 

standards and provides basic consumer utility. DOE used the baseline unit in the engineering 

analysis and the LCC and PBP analyses. To determine energy savings and changes in price, 

DOE compared each higher energy efficiency design option with the baseline unit. 

EPCA, as amended by EISA 2007, established the following energy and water 

conservation standards for dishwashers manufactured on or after January 1, 2010 (42 U.S.C. 

6295(g)(10)), which DOE has incorporated into its analysis as the baseline efficiency levels: 

• Standard dishwashers – 355 kilowatt-hours per year (kWh/year) and 6.5 gallons 

per cycle; and

• Compact dishwashers – 260 kWh/year and 4.5 gallons per cycle. 

5.3.2 Incremental Efficiency Levels

5.3.2.1 Standard Product Class

DOE analyzed several efficiency levels for standard dishwashers, and obtained 

incremental cost data at each of these levels. Table 5.3.1 includes the analyzed efficiency levels 

and the reference source of each level for the standard product class.
5-4

Table 5.3.1 Standard Dishwasher Efficiency Levels, Based on Annual Energy Use and 

Water Consumption

Level Efficiency Level Reference Source

Efficiency Level

Annual 

Energy Use

(kWh/year)

Water 

Consumption

(gallons/cycle)

Baseline DOE Standard 355 6.5

EL 1 ENERGY STAR (current) 324 5.8

EL 2 CEE Tier 1/Consensus Agreement 307 5.0

EL 3 CEE Tier 2/future ENERGY STAR (effective January 20, 2012) 295 4.25

EL 4 Gap Filla 234 3.8

EL 5 Maximum Availablea 180 1.6

a) Source: ENERGY STAR-qualified dishwashers as of July 13, 2011.

DOE analyzed five efficiency levels beyond the baseline. These levels were based on the 

current and future ENERGY STAR levels, the Consortium for Energy Efficiency (CEE) 

Residential Dishwasher Initiative efficiency tiers, and the maximum level that is currently 

commercially available (which DOE used as a proxy for max-tech) as determined from data 

contained within the California Energy Commission (CEC) and ENERGY STAR product 

databases. DOE added a gap-fill level to span the large difference in efficiency between the CEE 

Tier 2 and maximum available level. Efficiency Level 2 also corresponds to the standard 

dishwasher efficiency level agreed upon in a consensus agreement jointly submitted to DOE by 

AHAM and the American Council for an Energy-Efficient Economy (ACEEE), also on behalf of 

multiple manufacturers, efficiency advocates, and consumer groups. (See chapter 3 of the direct 

final rule TSD for further description of this “Consensus Agreement.”)

EPCA mandates that DOE analyze the maximum technologically feasible (max-tech) 

model, based on a minimum annual energy use and a minimum water consumption for 

residential dishwashers. The two variables are related to a certain extent (via external and 

internal water heating energy consumption) and DOE evaluates the relative importance of each 

metric in setting the energy conservation standards. It is not certain that a residential dishwasher 

with the lowest possible annual energy use will also achieve the lowest possible water 

consumption. Similarly, a dishwasher with the lowest water consumption may not achieve the 

lowest annual energy use. However, for residential dishwashers currently available on the 

market, the units achieving the lowest annual energy use also achieve the lowest water 

consumption, and therefore represent the max-tech level.

5.3.2.2 Compact Product Class

The Consensus Agreement includes a proposed energy conservation standard for the 

compact product class. EPCA, as amended, allows DOE to issue a final rule establishing an 

energy conservation standard on receipt of a statement submitted jointly by interested persons 

that are fairly representative of relevant points of view (including representatives of 

manufacturers of covered products, States, and efficiency advocates) that contains 

recommendations with respect to an energy conservation standard that are in accordance with the 
5-5

provisions of 42 U.S.C. 6295(o). The standards proposed in the Consensus Agreement are based 

on annual energy use and water consumption. 

Table 5.3.2 below shows the current DOE standard for the compact product class, the 

efficiency level proposed in the Consensus Agreement, and the max-tech level. DOE only 

analyzed two efficiency levels beyond the baseline because the number of compact dishwasher 

models commercially available is too small to warrant any gap-fill levels. 

Table 5.3.2 Efficiency Levels for Compact Residential Dishwashers

Level Efficiency Level Description

Annual Energy 

Use

(kWh/year)

Water 

Consumption

(gal/cycle)

Baseline DOE Standard 260 4.5

EL 1 Consensus Agreement/future ENERGY STAR (effective 

January 20, 2012) 222 3.5

EL 2 Maximum Availablea 154 2.1

a) Source: ENERGY STAR-qualified dishwashers as of July 13, 2011.

5.4 METHODOLOGY OVERVIEW

DOE relied on multiple sources of information for this engineering analysis. These 

sources include an AHAM data submittal, manufacturer interviews, product teardowns, a review 

of TSDs from previous rulemakings, and internal product testing.

5.4.1 AHAM Data Request 

In support of this rulemaking effort, DOE requested data from AHAM for residential 

dishwashers. The data represent shipments, shipment-weighted average efficiency, and market 

share efficiency data. A discussion of the data provided by AHAM is included in section 5.5.1.

The data submittal did not include manufacturing cost information.

5.4.2 Manufacturer Interviews

DOE understands that there is variability among manufacturers in baseline units, design 

strategies, and cost structures. To better understand and explain these variances, DOE conducted

manufacturer interviews. These confidential interviews provided a deeper understanding of the 

various combinations of technologies used to increase residential dishwasher efficiency, and 

their associated manufacturing costs. Sample questions asked during the interviews are contained 

in appendix 12-A.

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

required to increase the efficiency of the baseline units to various efficiency levels (i.e.,

conversion capital expenditures by efficiency or energy-use level). The interviews provided 
5-6

information about the size and the nature of the capital investments. DOE also requested 

information about the depreciation method used to expense the conversion capital. The 

manufacturer impact analysis in chapter 12 of the direct final rule TSD includes a discussion of

this information obtained during manufacturer interviews.

5.4.3 Product Teardowns

Other than obtaining detailed manufacturing costs directly from a manufacturer, the most 

accurate method for determining the production cost of a product is to disassemble representative

units piece-by-piece and estimate the material, labor, and overhead costs associated with each 

component using a process commonly called a physical teardown. A supplementary method, 

called a catalog teardown, uses published manufacturer catalogs and supplementary component 

data to estimate the major physical differences between a product that has been physically 

disassembled and another similar product. DOE performed physical teardown analysis on both 

standard and compact dishwashers. The teardown methodology is explained in the following 

sections.

5.4.3.1 Selection of Units

DOE generally adopts the following criteria for selecting units for teardown analysis:

• The selected products should span the full range of efficiency levels for each product class 

under consideration;

• Within each product class, the selected products should, if possible, come from the same 

manufacturer and belong to the same product platform;

• The selected products should, if possible, come from manufacturers with large market shares

in that product class, although the highest efficiency products are chosen irrespective of 

manufacturer; and

• The selected products should have non-efficiency-related features that are the same as, or 

similar to, features of other products in the same class and at the same efficiency level.

5.4.3.2 Generation of Bill of Materials

The end result of each teardown is a structured BOM, which describes each product part

and its relationship to the other parts, in the estimated order of assembly. The BOMs describe 

each fabrication and assembly operation in detail, including the type of value—added equipment 

needed (e.g., stamping presses, injection molding machines, spot-welders, etc.) and the estimated

cycle times associated with each conversion step. The result is a thorough and explicit model of 

the production process.

Materials in the BOM are divided between raw materials that require conversion steps to 

be made ready for assembly, while purchased parts are typically delivered ready for installation.

The classification into raw materials or purchased parts is based on DOE’s previous industry 

experience, recent information in trade publications, and discussions with original equipment 
5-7

manufacturers (OEMs). For purchased parts, the purchase price is based on volume-variable 

price quotations and detailed discussions with suppliers.

For parts fabricated in-house, the prices of the underlying “raw” metals (e.g., tube, sheet 

metal) are estimated on the basis of 5-year averages to smooth out spikes in demand. Other 

“raw” materials such as plastic resins, insulation materials, etc. are estimated on a current-market 

basis. The costs of raw materials are based on manufacturer interviews, quotes from suppliers, 

secondary research, and by subscriptions to publications including the American Metals Marketb

5.4.3.3 Cost Structure of the Spreadsheet Models

(AMM). Past price quotes are indexed using applicable Bureau of Labor Statistics producer 

price index tables as well as AMM monthly data. 

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

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

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

manufacturing cost.

Figure 5.4.1 Manufacturing Cost Assessment Stages

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

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

dismantled, and each part was characterized according to weight, manufacturing processes used, 

dimensions, material, and quantity. The BOM incorporates all materials, components, and 

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

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

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

conducted with manufacturers to ensure accuracy on methodology and pricing.

Following the development of a detailed BOM, the major manufacturing processes were 

identified and developed for the spreadsheet model. Some of these processes are listed in Table 

5.4.1.

 

b For information on American Metals Market, please visit: www.amm.com.
5-8

Table 5.4.1 Major Manufacturing Processes

Fabrication Finishing Assembly/Joining Quality Control

Fixturing

Stamping/Pressing

Brake Forming

Cutting and Shearing

Insulating

Turret Punch

Tube Forming

Enameling

Washing

Powder Coating

De-burring

Polishing

Refrigerant Charging

Adhesive Bonding

Spot Welding

Seam Welding

Packaging

Inspecting & Testing

Fabrication process cycle times for each part made in-house were estimated and entered 

into the BOM. Based on estimated assembly and fabrication time requirements, the labor 

content of each appliance could be estimated. For this analysis, $24.00 per hour was used as the 

average fully-burdened labor rate based on typical annual wages and benefits of industry 

employees.

Cycle requirements for fabrication steps were similarly aggregated by fabrication 

machine type while accounting for dedicated vs. non-dedicated machinery and/or change-over 

times (die swaps in a press, for example). 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 unit costs: material, labor, and overhead. 

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

cost model and are cost-estimated individually. Thus, various implementations of design options 

can be accommodated, ranging from assemblies that are entirely purchased to units that are made 

entirely from raw materials. Hybrid assemblies, consisting of purchased parts and parts made on 

site are thus also accommodated.

5.4.3.4 Cost Model and Definitions

The cost model is based on production activities and divides factory costs into the 

following categories:

• Materials: Purchased parts (i.e., motors, valves, 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.

Cost Definitions

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

defined the above terms as follows:
5-9

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

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.

• Supervisory labor: Labor associated with fabrication and assembly basis. Assigned on a 

span basis (x number of employees per supervisor) that depends on the industry.

• Indirect labor: Labor costs that scale with fabrication and assembly labor. These included 

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

proportional to all other labor. 

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

replacement as the production equipment is amortized. All depreciation is assigned in a 

linear fashion and affected equipment life depends on the type of equipment.

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

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

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

that feed and/or make up the assembly line.

• Utilities: Electricity, gas, telephones, etc.

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

• Insurance: Appropriated as a function of unit cost.

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

5.4.3.5 Cost Model Assumptions

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

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

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

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

Site visits allowed DOE to confirm its cost model assumptions through direct observation of the 

manufacturing plant, as well as through manufacturer interviews, reviews of current Bureau of 

Labor Statistics data, etc.

5.4.4 Review of Previous Technical Support Documents and Models

DOE reviewed previous rulemaking TSDs to assess their applicability to the current 

standard setting process for residential dishwashers. These previous rulemaking TSDs served as 

a source for design options and energy consumption analysis, in addition to other sources.
5-10

5.4.5 Product Testing

Much of the analysis in this chapter relies on data from publicly available sources such as 

the CEC and ENERGY STAR databases. However, DOE also conducted its own limited 

performance testing according to the DOE test procedure for the following purposes:

• Verify performance trends that are apparent in the publicly available data;

• Develop a better understanding of the design options and product features 

currently available on the market; and

• Develop a better understanding of the operational characteristics of residential 

dishwashers.

5.5 ANALYSIS AND RESULTS

5.5.1 AHAM Data

To support the DOE rulemaking, AHAM collected shipment and efficiency data from its 

member companies. For reasons of product availability and number of manufacturers, AHAM 

did not provide disaggregated data for compact dishwashers. Table 5.5.1 compiles unit shipment 

data for residential dishwashers from 2000 to 2010. The data is split between portable and builtin units, however these distinctions do not correspond to the compact and standard product 

classes.

Table 5.5.1 AHAM Residential Dishwasher Shipments Data Submittal

Year Total Shipments Portable Built-In

2000 5,827,678 164,425 5,663,253

2001 5,627,373 149,372 5,478,001

2002 6,206,792 158,131 6,048,661

2003 6,428,351 148,092 6,280,259

2004 7,105,511 152,968 6,952,543

2005 7,424,196 133,204 7,290,992

2006 7,251,504 129,777 7,121,727

2007 6,976,830 110,213 6,866,617

2008 5,995,124 91,693 5,903,431

2009 5,403,652 70,278 5,333,374

2010 5,710,406 65,544 5,644,862

Table 5.5.2 reproduces AHAM's data submittal for the shipment-weighted average 

efficiency levels for all residential dishwasher shipments. The data show the shipment-weighted 

energy use in kWh per cycle as well as the calculated annual energy use for the total industry.

The calculated annual energy use values assume 215 cycles per year, but do not account for 

annual standby energy consumption as in the current DOE test procedure, and therefore likely 

slightly underestimate the actual representative shipment-weighted average annual energy use.
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Table 5.5.2 AHAM Residential Dishwasher Shipment-Weighted Average Efficiency Data 

Submittal

Year Shipment-Weighted Average Energy Use 

(kWh/cycle)

Calculated Shipment-Weighted Average Annual 

Energy Use (kWh/year)

2000 2.00 430

2001 1.92 413

2002 1.84 396

2003 1.83 393

2004 1.68 361

2005 1.67 359

2006 1.63 350

2007 1.53 329

2008 1.52 327

2009 1.45 312

2010 1.37 295

a) Based on 215 cycles per year. Does not account for annual standby energy consumption.

AHAM provided market share efficiency data for residential dishwashers for 2008 to 

2010, as shown in Table 5.5.3. For some entries, market share data are provided combining 

multiple efficiency levels. In these cases, AHAM has combined the efficiency levels to maintain 

manufacturer confidentiality.

Table 5.5.3 AHAM Residential Dishwasher Market Share Efficiency Data Submittal

Efficiency 

Level

Annual Energy Use 

Range (kWh/year)

Average Water Consumption 

(gallons/cycle, 2009)

Market Share (percent)c

2008 2009 2010

Baseline 325 – 355 4.84 51.2% 37.3% 3.8%

EL1 308 – 324 4.38 27.2% 39.7% 51.7%

EL2 296 – 307 5.09 7.1% 8.6% 21.5%

EL3 235 – 295 4.7 5.3%a 10.8%b 22.8%b

EL4 181 – 234 2.7 n/a n/a n/a

EL5 ≤ 180 2.63 0.0% n/a n/a

a) Includes levels 3 and 4.

b) Includes levels 3, 4, and 5.

c) Numbers may not add exactly to 100%

5.5.2 Product Teardowns

DOE conducted a market survey of residential dishwasher models and their associated 

features. After reviewing the model data, DOE selected 12 standard and 3 compact dishwashers 

for teardowns. These selections were based on the proposed efficiency levels and the range of 

product efficiencies and features available on the market. DOE conducted the dishwasher 

teardowns to identify design features and corresponding manufacturing costs that are associated 

with successively higher efficiency levels. Table 5.5.4 lists features typical of the selected units

in the standard product class at the corresponding analyzed efficiency levels.
5-12

Table 5.5.4 Standard Residential Dishwasher Features

Feature Standard Residential Dishwasher Features by Efficiency Level

Baseline EL 1 EL 2 EL 3 EL 4 EL 5

Annual Energy 

Use 

(kWh/year)

355 324 307 295 234 180

Water 

Consumption 

(gallons/cycle)

6.5 5.8 5.0 4.25 3.8 1.6

Control Type Electromechanical Electronic Electronic Electronic Electronic Electronic

Soil Sensing No No Yes Yes Yes Yes

Drying Type Heat Dry Heat Dry Heat Dry Condensation Condensation Condensation

Insulation/Tub 

Type

Non-Insulated 

Plastic

Non-Insulated 

Plastic

Insulated 

Plastic

Insulated 

Plastic

Insulated 

Plastic

Insulated

Plastic

Heater Type Tubular, Intub Tubular, In-tub Tubular, Intub

In-line FlowthroughIn-line FlowthroughIntegrated in 

Pump

Temperature 

Sensing

Temperature 

Switch

Temperature 

Switch

Temperature 

Switch

Temperature 

Sensor

Temperature 

Sensor

Temperature 

Sensor

Water Fill 

Control Timed Fill Timed Fill Timed Fill Flow Meter Flow Meter Flow Meter

Water Filter

Large Particle 

Plastic Filter 

+ Disposal

Large Particle 

+ Fine (SS)

Large 

Particle + 

Fine (SS)

Large 

Particle + 

Fine (SS)

Large 

Particle + 

Fine (SS)

Large Particle 

+ Fine (SS)

Spray System 1-Arm 

w/Tower

Multiple Arms, 

No Diverter

Multiple 

Arms, No 

Diverter

Multiple 

Arms, No 

Diverter

Multiple 

Arms, w/ 

Diverter

Multiple Arms, 

w/ Diverter

Power Supply N/A Linear Switch 

Mode Switch Mode Switch Mode Switch Mode

Pump Motor 

Technology 1-Speed 1-Speed Variable Speed

Variable 

Speed

Variable 

Speed Variable Speed

Drain Pump No Separate 

Drain Pump

Yes Yes Yes Yes Yes

Hydraulic 

System 

Optimization

None None Partial –

Water Lines

Complete –

Sump and 

Water Lines

Complete –

Sump and 

Water Lines

Complete –

Sump and 

Water Lines

Control 

Strategies N/A N/A Longer Cycles

Longer 

Cycles

Lower 

Wash/Rinse 

Temperatures

Lower 

Wash/Rinse 

Temperatures

5.5.2.1 Baseline Construction: Standard Dishwasher

The baseline standard dishwasher is equipped with electromechanical controls that allow 

the user to select specific cycle settings. This includes a switch for selecting the power dry 

option and a rotary dial to initiate and set the cycle duration. Because the electromechanical 

controls are used, the standby mode and off mode power consumption are zero.

The wash tub is made of plastic using an injection molding process, with no added 

insulation. Inside the tub are upper and lower racks for loading the dishware. The baseline 

dishwasher has only one spray arm at the base of the tub, with a spray tower that extends up into
5-13

the tub when water circulates. A tubular resistance heater, a coarse plastic filter, and an overflow 

float switch also sit at the base of the tub.

The water system includes a one-speed motor that drives a pump to circulate water within 

the tub and to drain water out of the unit, depending on the position of a solenoid valve in the 

water lines. Because the baseline unit has only a coarse plastic filter, the motor also drives a 

disposal to break down food particles that would make it into the water lines. The baseline unit 

uses timed fills to control the volume of water entering the unit, with no flow meter or fill level 

pressure switch.

Based on product teardowns, DOE developed the following baseline production and 

materials cost distributions for a standard dishwasher. Table 5.5.5 and Figure 5.5.1 show the 

baseline production cost distributions; and Table 5.5.6 and Figure 5.5.2 show the baseline 

materials cost distribution. Depending on the manufacturer and the production volume, the 

depreciation costs may vary from those shown in the figures, which assume a “green-field” site.

Table 5.5.5 Baseline Standard Dishwasher Production Cost Distribution

Cost Category

Total 

Cost

($2010)

Figure 5.5.1 Baseline Standard Dishwasher Production Cost 

Distribution

Raw Materials $42.63

Purchased Parts $77.29

Assy Labor Cost $12.21

Fab Labor Cost $12.26

Supervision Cost $1.27

Indirect Labor Cost $8.50

Equipment Dep. Cost $5.08

Tooling Dep. Costs $10.16

Building Dep. Cost $5.33

Indirect Process Cost $3.17

Maintenance $5.09

Utility Cost $2.58

Property Tax $3.90

Insurance $1.52

Total $ 190.98
5-14

Table 5.5.6 Baseline Standard Dishwasher Materials Cost Distribution

Sub-Assembly

Total 

Materials 

Cost ($2010)

Figure 5.5.2 Baseline Standard Dishwasher Materials 

Cost Distribution

Packaging $10.99

Final Assy $17.56

Shell $15.50

Water System $40.74

Racks $13.83

Controls $14.84

Wiring Harness $6.05

Vent $0.41

Total $ 119.92

5.5.2.2 Baseline Construction: Compact Dishwasher

The baseline compact dishwasher is a countertop unit that incorporates many design 

features used to minimize energy and water consumption. The electronic controls on the 

baseline model allow for more complex control strategies compared to a unit with 

electromechanical controls. The electronic controls employ a linear power supply, with an 

associated standby and off mode power consumption of 2.3 watts. The unit includes a flow 

meter and pressure switch for fill control, and a temperature sensor to control the heater 

operation. 

The tub on the baseline unit is made of stainless steel with bitumen insulation on the 

exterior to improve the unit’s noise performance. The tub only includes one dish rack and one 

spray arm because multiple racks cannot fit into the more compact volume. It uses a flowthrough water heater integrated into the sump as opposed to a tubular in-tub heating element, 

which leaves more volume in the tub available for loading dishes. 

The baseline compact dishwasher has more effective water filtering than the baseline 

standard unit. It includes a coarse stainless steel filter, and a finer stainless steel mesh filter to 

catch smaller food particles. No disposal is necessary because large food particles do not pass

through these filters into the water system.

Based on product teardowns, DOE developed the following baseline production and 

materials cost distributions for a compact dishwasher. Table 5.5.7 and Figure 5.5.3 show the 

baseline production cost distributions; and Table 5.5.8 and Figure 5.5.4 show the baseline 

materials cost distribution. Depending on the manufacturer and the production volume, the 

depreciation costs may vary from those shown in the figures, which assume a “green-field” site.
5-15

Table 5.5.7 Baseline Compact Dishwasher Production Cost Distribution

Cost Category

Total 

Cost

($2010)

Figure 5.5.3 Baseline Compact Dishwasher Production Cost 

Distribution

Raw Materials $50.48

Purchased Parts $78.59

Assy Labor Cost $12.19

Fab Labor Cost $7.32

Supervision Cost $1.01

Indirect Labor Cost $6.77

Equipment Dep. Cost $3.79

Tooling Dep. Costs $6.61

Building Dep. Cost $4.96

Indirect Process Cost $2.17

Maintenance $3.80

Utility Cost $2.76

Property Tax $3.79

Insurance $1.47

Total $ 185.71

Table 5.5.8 Baseline Compact Dishwasher Materials Cost Distribution

Sub-Assembly

Total 

Materials 

Cost ($2010)

Figure 5.5.4 Baseline Compact Dishwasher Materials 

Cost Distribution

Packaging $5.90

Final Assy $11.90

Shell $23.07

Water System $41.30

Racks $5.71

Controls $34.39

Wiring Harness $6.80

Total $ 129.07

5.5.2.3 Construction at Higher Efficiency Levels

Based on the design options retained from the screening analysis (see chapter 4 of the 

direct final rule TSD), the reverse-engineering analyses, and discussions with manufacturers, 
5-16

summarized in section 5.5.4, DOE developed manufacturing costs associated with various design 

features necessary to achieve higher efficiencies.

The following are the design changes DOE believes manufacturers would typically use to 

meet each efficiency level. These configurations were subsequently modeled to obtain 

incremental manufacturing cost estimates.

Standard Dishwashers

Efficiency Level 1

Based on characteristics of units selected for teardown and based on discussions with 

manufacturers, DOE research suggests that efficiency level (EL) 1 is typically achieved in 

standard dishwashers through the following incremental changes to the baseline unit described in 

section 5.5.2.1:

1. Electronic Controls

Through its observations and discussions with manufacturers, DOE believes that in 

moving from the baseline level to EL 1, manufacturers would likely replace electromechanical 

controls with electronic controls. This would allow for more sophisticated control during the 

cycle, which could result in more precise timing and feedback control, eliminating excess energy 

and water consumption. The electronic controls at EL 1 would likely employ a linear power 

supply. The standby mode and off mode power consumption associated with the electronic 

controls are 2.3 watts.

2. Multiple Spray Arms

At EL 1, the single spray arm and spray tower of the baseline unit are likely replaced by 

two separate spray arms – one dedicated to each rack of dishes. This helps reduce water 

consumption by more accurately directing the water to the dishes. Less water is needed while 

still ensuring the dishes are washed effectively.

3. Improved Water Filters

The coarse water filter in the baseline dishwasher allows food to pass through to the 

macerator. After the food is broken down, pieces still make their way through the water system, 

so the lines and spray arms must allow the food particles to pass through to prevent clogs. At EL 

1, manufacturers would likely add a finer food filter using perforated stainless steel. By trapping 

smaller food particles and eliminating the food disposer, the typical unit at EL 1 can use smaller 

tube diameters and thinner spray arms without clogging, decreasing the total volume of the water 

system.

4. Separate Drain Pump

The baseline unit uses a single pump to circulate water within the dishwasher and to drain 

water out of the unit. At EL 1, manufacturers would likely include a separate pump and motor 

dedicated to draining water from the unit. Circulating water within the unit requires a stronger 

motor than for draining the water, so the EL 1 unit avoids the excess energy consumption 

associated with using the circulating motor to pump water out of the unit.
5-17

Efficiency Level 2

Through research and discussions with manufacturers, DOE believes that manufacturers 

would likely improve on the other design options used for EL 1, and would incorporate certain 

additional features to reach EL 2:

1. Soil Sensing

A dishwasher meeting EL 2 likely incorporates more advanced controls, including a 

turbidity sensor. The turbidity sensor monitors the clarity of the water passing through the sump, 

and adjusts the wash cycle accordingly. As a result, the dishwasher can adjust to use less water 

and energy for less-soiled dish loads.

2. 3-Phase Variable-Speed Motor

The EL 2 dishwasher would likely feature a variable-speed motor to drive the circulation 

pump. This allows the dishwasher to adjust the speed water is pumped throughout the water 

system depending on the point during the cycle. Using the most energy-intensive pump 

operation only when needed eliminates excess energy consumption for portions of the wash 

cycle using less aggressive circulation.

3. Hydraulic System Optimization

At EL 2, manufacturers would likely further decrease the capacity of the water system by 

optimizing the water lines and spray arms. This includes both decreasing the volume of the fill 

lines and spray arms, and moving the main water feed line to the tub interior, thereby decreasing 

its length.

4. Control Strategies

As manufacturers decrease energy and water consumption, they increase certain other 

wash cycle parameters to maintain washing performance. At EL 2, manufacturers would likely 

increase the duration of the cycle to compensate for decreased water use. Running the 

dishwasher for a longer period of time has a minor energy penalty, but it is outweighed by the 

corresponding decrease in water heating and machine electrical consumption.

5. Tub Insulation

With the high temperatures generated during a dishwashing cycle, the unit can lose a 

significant amount of heat through the plastic tub walls. At EL 2, manufacturers would likely 

add a cotton jacket to help keep the heat within the tub. This differs from units with stainless 

steel tubs and bitumen insulation; for those units, the bitumen is used to aid in noise 

performance, and actually has a corresponding energy penalty due to the added thermal mass.

6. Switch Mode Power Supply

At EL 2, manufacturers would likely switch from a linear power supply to a switch mode 

power supply. This decreases the amount of energy consumed by the unit when it is in standby 

mode or off mode. The standby mode and off mode power consumption associated with the 

electronic controls using a switch mode power supply are 1.7 watts.

Efficiency Level 3
5-18

A dishwasher at EL 3 is likely to employ many of the same design features as one at EL 

2. The major incremental changes associated with the decreased energy and water consumption 

at this level are:

1. Flow-Through Water Heater

Baseline through EL 2 dishwashers likely use a tubular, in-tub water heater. This 

requires a certain volume of standing water within the tub in addition to the volume of the sump 

and water lines. At EL 3, manufacturers would likely use a flow-through water heater located

below the tub next to the sump assembly. This allows for effective water heating with a smaller 

volume of standing water.

2. Condensation Drying

Without the typical tubular in-tub water heater from the previous levels, manufacturers 

would likely eliminate the heated drying option. Heated drying uses the resistance heater to 

warm the air in the tub and evaporate the water off the dishes. Condensation drying uses a 

higher temperature final rinse to raise the temperature of the dishes, and then uses a fan to 

introduce cooler air from the kitchen to cool the wash tub walls where the evaporated water 

condenses. The condensation drying strategy uses less energy compared to the heated drying 

method.

3. Hydraulic System Optimization

At EL 3, manufacturers would likely further decrease the total volume of the water 

system. In addition to using smaller supply lines and spray arms, EL 3 would incorporate a 

redesigned sump with a smaller internal volume.

4. Temperature Sensor

Baseline through EL 2 dishwashers typically include temperature switches to control the 

water heater. At EL 3, manufacturers would likely switch to a temperature sensor to allow for 

closed-loop control, rather than timed heating with a maximum cutoff point determined by the 

switch. Better temperature control results in less energy use associated with internal water 

heating.

5. Flow Meter

At EL 3, manufacturers would likely switch from timed fill control to using a water flow 

meter. A flow meter with an electronic controller allows a dishwasher to dose water very 

precisely, even at varying supply pressures. This reduces the excess energy and water 

consumption associated with overfilling the dishwasher, and helps prevent poor wash 

performance caused by under-filling.

Efficiency Level 4

At EL 4, DOE believes manufacturers would likely make four incremental changes to the 

unit described for EL 3:
5-19

1. Water Diverter Assembly

DOE believes manufacturers would likely incorporate a water diverter valve at EL 4. 

The diverter directs the flow of water from the circulating pump to either the top or bottom spray 

arm depending on its position. This allows the dishes in both the top and bottom racks to receive 

the same spray volume, while maintaining a smaller volume of water in the sump and water 

lines. This technology may also correspond to a further increase in cycle duration as both racks 

are not washed simultaneously.

2. Control Strategies

To further decrease energy consumption at EL 4, DOE believes manufacturers would 

decrease wash and/or rinse temperatures. This decreases the amount of energy consumed for 

water heating (both internal and external), but has the potential to hurt wash performance.

3. Improved Filters

At EL 4, manufacturers would likely further improve the water filtering system. For EL 

1 through EL 3, the finest filters use perforated stainless steel. The fine filter at EL 4 would 

likely switch to a woven stainless steel cloth, which is capable of trapping even smaller food 

particles. This further decreases the potential for clogging in the water system, leading to 

decreased water consumption.

4. Humidity Sensor

In addition to the condensation drying system at EL 3, manufacturers would likely add a 

humidity sensor at EL 4. This sensor detects when the humidity in the tub reaches a certain level 

indicating the dishes are dry, and shuts off the fan drawing cool air into the tub. This eliminates 

the small amount of excess energy consumption associated with running the fan after the air in 

the tub is sufficiently dry.

Efficiency Level 5

To reach the minimum energy and water consumption levels for standard dishwashers 

currently available, manufacturers would likely make the following two changes:

1. In-Pump Heater

At EL 5, manufacturers would likely replace the flow-through water heater with a design 

that incorporates the heating element into the circulation pump. This design change eliminates 

the water volume necessary to fill the water lines to the flow-through heater, and to fill the heater 

itself. This design change also requires a further redesign of the sump assembly.

2. Remove Vent Fan

DOE believes that dishwashers at EL 5 would likely also eliminate the air circulation fan. 

This saves the small amount of energy associated with running the fan after the final rinse cycle, 

but also decreases the drying performance of the unit.
5-20

Compact Dishwashers

Starting with the baseline compact dishwasher described in section 5.5.2.2, DOE believes 

manufacturers would incorporate incremental changes to reach EL 1 and EL 2. As described in 

section 5.3.2.2, DOE only analyzed two efficiency levels beyond the baseline due to the small 

number of compact dishwasher models available on the market.

Efficiency Level 1

The baseline compact dishwasher already incorporates many of the design options used 

to decrease energy and water consumption in standard dishwashers. As a result, the baseline unit 

performs significantly better than the DOE standard, and nearly reaches the energy and water 

consumption levels specified for EL 1. To improve the unit’s performance to meet the EL 1 

levels, DOE believes manufacturers would likely alter the control system to use slightly less 

water, and possibly to increase the cycle duration.

Efficiency Level 2

The max-tech dishwasher available on the market is a dish drawer instead of a countertop 

unit. The configuration of dish drawers makes them significantly more expensive to 

manufacture compared to a countertop unit. However, DOE believes the design features used in 

the max-tech unit could be incorporated into a countertop platform. The features DOE expects 

manufacturers to use to reach EL 2 are listed below:

1. Permanent Magnet Motor

DOE believes manufacturers would switch to a permanent magnet motor to reach EL 2. 

With this type of motor, the pump impeller is attached directly to the rotor, so no drive system is 

required. Additionally, manufacturers would likely use this motor for both circulating water 

during the wash or rinse cycles and for pumping water out of the unit, depending on which 

direction the rotor spins.

2. Heater Incorporated into Base of Tub

DOE observed that the max-tech compact dishwasher incorporates the internal water 

heater into the base of the tub. This requires a lower volume of water sitting in the bottom of the 

tub than a tubular in-tub water heater, and eliminates the volume required to fill a flow-through 

water heater.

3. Reduced Sump Volume

Combined with the two design options listed above, DOE expects manufacturers would 

decrease the sump volume to the extent that it would only house the pump impeller. Because 

there is no heater integrated in the sump, and only one pump impeller housing, the volume of 

water required to fill the sump and water lines is much less than for the sump configuration on 

the baseline and EL 1 units. 

4. Switch Mode Power Supply

At EL 2, manufacturers would likely switch from a linear power supply to a switch mode 

power supply. This decreases the amount of energy consumed by the unit when it is in standby 
5-21

mode or off mode. The standby mode and off mode power consumption associated with the 

electronic controls using a switch mode power supply are 1.7 watts.

5.5.3 Cost-Efficiency Curves

Based upon product teardowns and cost modeling, DOE developed the following costefficiency relationships for standard and compact residential dishwashers. The corresponding 

cost-efficiency curves are shown as follows.

5.5.3.1 Standard Dishwashers

For standard dishwashers, DOE developed incremental manufacturing costs by tearing 

down 12 units, and creating a cost model at each efficiency level. DOE started with the baseline 

unit cost model, and at each higher efficiency level, added in the observed changes associated 

with improving efficiency. By doing this, DOE excluded the costs of any non-efficiency related 

components from the more efficient units. The more efficient units are generally sold at a higher 

price point, and sometimes include features that increase manufacturing cost, but are not 

necessarily efficiency-related. One example of such a feature is the typical use of stainless steel 

wash tubs in more expensive units. Table 5.5.9 shows the incremental manufacturing costs from 

DOE’s reverse-engineering analysis.

Table 5.5.9 Standard Dishwasher Incremental Manufacturing Costs

Efficiency Level

(Annual Energy 

Use, kWh/year)

Incremental Costs

($2010) ($/kWh) ($/gal)

Baseline (355) - - -

EL 1 (324) $18.27 $0.59 $26.10

EL 2 (307) $31.82 $0.66 $21.21

EL 3 (295) $69.23 $1.15 $30.77

EL 4 (234) $75.18 $0.62 $27.85

EL 5 (180) $82.95 $0.47 $16.93

5.5.3.2 Compact Dishwashers

DOE developed the compact product class incremental manufacturing costs based on 

teardowns of three units. As with the standard product class, DOE started with the baseline unit 

cost model, and at each higher efficiency level, added in the observed changes associated with 

improving efficiency. There are very few, disparate compact platforms (i.e. countertop units and 

dishdrawers) available on the market. Therefore, DOE weighted the costs at each efficiency 
5-22

level by market share of each platform. Table 5.5.10 shows the incremental manufacturing costs 

for compact dishwashers as a result of DOE’s reverse-engineering analysis.

Table 5.5.10 Compact Dishwasher Incremental Manufacturing Costs

Efficiency Level

(Annual Energy 

Use, kWh/year)

Incremental Costs 

($2010) ($/kWh) ($/gal)

Baseline (260) - - -

EL 1 (222) $1.00 $0.03 $1.00

EL 2 (154) $12.11 $0.11 $5.05

5.5.4 Manufacturer Interviews

DOE conducted interviews with residential dishwasher manufacturers to develop a better 

understanding of current product features and the technologies used to improve energy 

efficiency. The manufacturers interviewed represent a wide range of U.S. market share and 

included both domestic and international companies that sell residential dishwashers in the 

United States. During these interviews, DOE asked manufacturers questions about the following 

topics related to the engineering analysis:

• Design features of current baseline products

• Proposed incremental efficiency levels

• Design options required to meet each efficiency level

• Impacts on consumer utility

• Installation and repair costs as a function of efficiency

The discussion helped DOE understand what proposed design options have already been 

implemented and what additional design options DOE should consider. The manufacturers 

typically based their comments only on the standard product class because of the limited 

production of compact units.

The discussion below represents a consolidation of the manufacturer responses.
5-23

5.5.4.1 Design Features of Current Baseline Products

DOE discussed with manufacturers the features of baseline products identified during the 

reverse-engineering analysis. The manufacturers generally agreed with DOE’s assumptions for a 

baseline unit, although not all manufacturers produce products at the baseline efficiency level. 

5.5.4.2 Proposed Incremental Efficiency Levels

DOE asked manufacturers to comment on the proposed efficiency levels for the standard 

and compact product classes. Manufacturers were asked to comment on the appropriateness of 

each incremental efficiency level, including the gap-fill levels and the max-tech levels. In 

general, manufacturers did not object to the efficiency levels DOE selected for analysis. While 

discussing the proposed efficiency levels, multiple manufacturers expressed concerns with 

performance at the highest efficiency level, as discussed below in section 5.5.4.4.

5.5.4.3 Design Options Required to Meet Each Efficiency Level

DOE asked manufacturers to describe the changes associated with each active mode 

efficiency level relative to the baseline units in each product class. From the reverse-engineering 

analysis, DOE developed a list of design options at each efficiency level, and requested 

manufacturer feedback on the list during the interviews.

Manufacturers generally agreed with DOE’s initial association of design options with the 

efficiency levels. The design options discussed in section 5.5.2.3 represent the design options 

associated with each efficiency level based on DOE’s reverse-engineering analysis, and feedback 

from manufacturers during the interviews.

DOE also used the interviews as an opportunity to clarify which design options are 

actually associated with improved energy and water performance rather than consumer 

preference. For example, DOE learned that stainless steel wash tubs do not contribute 

significantly to a unit’s energy performance. Generally, consumers expect a stainless steel 

interior at higher price points, and more expensive units are generally more efficient. In 

addition, DOE learned that the bitumen insulation on steel tubs improves noise performance, and 

actually increases energy consumption due to the bitumen’s thermal mass.

5.5.4.4 Impact on Consumer Utility

Each manufacturer interviewed expressed that there would be some tradeoff with the 

performance of a unit at the higher efficiency levels. However, manufacturers differed in their 

opinions of how performance would be impacted. Certain manufacturers claimed wash 

performance could be maintained at all efficiency levels; however drying performance could be 

affected. Other manufacturers claimed that consumers would not be satisfied with wash 

performance at EL 4 and EL 5. All manufacturers agreed that a certain minimum amount of 
5-24

energy and water is required to effectively wash dishes, and that the consumption levels cannot 

continuously decrease.

Manufacturers also expressed concerns that consumers could be unhappy with the 

increasing length of cycles associated with more efficient units. The cycles lasting 2–3 hours are 

already at the limit consumers are willing to accept. Certain design options, such as a cold water 

inlet connection, would increase the cycle times even further. Certain manufacturers noted that 

achieving the energy and water use at EL 4 and EL 5 without significantly impacting consumer 

utility would require high-cost technology options.

5.5.4.1 Installation and Repair Costs as a Function of Efficiency

Manufacturers differed in their opinion of repair costs as a function of efficiency. Some 

manufacturers expect no change in typical repair costs for more efficient units, while others 

expect some increase due to more efficient units having more components. The manufacturers in 

general did not expect any major change in maintenance costs at higher efficiencies.

For installation costs, manufacturers pointed out that a cold water inlet connection, or 

dual hot and cold inlet connections, would increase installation costs. Dishwashers in the United 

States are typically connected to a hot water line, and as a result kitchens do not usually have a 

cold water line running to the dishwasher installation. For all other units, the manufacturers did 

not expect any change in installation costs.