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## Review of Survey Data to Support Revisions to DOE's Dishwasher Test Procedure

U.S. Department of Energy Energy Efficiency and Renewable Energy Office of Building Technology, State and Community Programs 1000 Independence Avenue, SW Washington, DC 20585

Date: December 18, 2001

Arthur D. Little, Inc. Acorn Park Cambridge, MA 02140Executive Summary To supportrevisions to the Department ofEnergy'stest procedures for measures ofenergy and water consumption in dishwashers, various survey data on consumers' dishwasher usage habits were collected from a number ofsources including several dishwasher manufacturers, detergent manufacturers, energy and consumer interest groups, independent researchers, and government agencies. The findings ofthe review ofavailable data on consumers' dishwasher usage habits showbroad support to define:
• Consumers' pretreatment methods,
• Distribution ofhouseholds by the level ofsoil in a dishwasher load,
• Quantitative amount ofsoil on the dishware, and
• Frequency ofhouseholds' use ofa dishwasher. Drawing from these survey findings, the existing test method for dishwashers, and ANSI!AHAM StauCiard DW-1, a weighted, three-point test method using different numbers ofsoiled dishware is recommended to measure the energy consumption ofsoil-sensing dishwashers. Itis further**rt~com;**nended that the number ofaverage-use cycles per year be reduced into the range of200 to 233 cycles per year.
Background The Department ofEnergy's Dishwasher Test Procedure is in the process ofbeing revised. The need to revise the test procedure is driven by the development ofadvanced soil-sensing dishwashers. The introduction in the mid-1990's ofadvanced dishwashers equipped with the ability to sense the soil level in the dishwasher and in response to adjust the wash cycle created a challenge to the DishwasherTest Procedure. The current test procedure, designed for fixed cycle dishwashers, measures energy consumptionusing a load ofclean dishes. Ithas been well demonstrated that soilsensing dishwashers yield lower energy consumption when tested with the clean load ofdishes, as compared to when tested with soiled dishes. Therefore, current energy consumptionresults for soilsensing dishwashers are not representative ofthe actual energy consumption ofsoil-sensing dishwashers inuse by consume:rs. This inaccuracy, created by the evolution oftechnology, necessitates revision ofthe Dishwasher Test Procedure. In addition to technology-driven change, consumers' usage ofdishwashers has also changed. The most notable change in dishwasher usage is the frequency ofits use. As the number ofoccupants in dishwasher-owning households has decreased, the occupants have grown older, and consumers eat more prepared or carryout foods, the frequency ofdishwasher usage has decreased significantly.

2

### - 

# '.
Overview of Current Dishwasher Test Procedure The Department ofEnergy's test procedures for measures ofenergy and water consumption (l0 CFR 430.23(c) ) call out measures for the energy factor (cycles perkilowatt-hour) and the estimated annual operating cost (dollars per year) ofdishwashers. These measures reference the Department ofEnergy's "Uniform Test Method for Measuring the Energy Consumption ofDishwashers" (10 CFR430 Subpt. B, App. C). The current test method operates a dishwasher onthe cycle recommended by the manufacturer for a full load ofnormally soiled dishes, butuses a test load ofclean dishes. The test load consists of8 place settings of dishware plus six serving pieces as specified in the industry-recognized standard, ANSI!AHAM Standard DW-1. The total per-cycle energy consumption ofa dishwasher is based on the energy consumption measured during this test run on the normal cycle with a load ofclean dishes. DishwashErs ml$tmeet orexceed a minimum energy factor (10 CFR430.32(f)). The energy factor for dishwa;;hers is the reciprocal ofthe total per-cycle energy consumption. Standard dishwashers (currently (qual**t~)** or greater than 22" in exterior width) must have an energy factor not less than 0.46 cycles/kWt. Compact dishwashers (currently, less than 22" in exterior width) must have an energy factor not**les~,** than 0.62 cycles/kWh. It should be notedthat effective: June 17, 2002 that the definitions ofstandard and compact dishwashers will be based on place setting capacity. A standard dishwasher will be one having a capacity greater than or equal to 8 place settings plus 6 serving pieces as defined in ANSI!AHAM Standard DW-1. Acompact dishwasher will be one having a capacity less than 8 place setting plus 6 serving pieces. The estimated annual operating cost for a dishwasher is listed on a dishwasher's Energy Guide label to assist consumers in making purchasing decisions. The estimated annual operating cost for a dishwasher is based onthe total per-cycle energy consumption, the representative average-use cycles per year, and the representative unit cost ofenergy.

Needed Test Procedure Revisions and Supporting Data Requirements As mentioned previously, it has been well demonstrated that soil-sensing dishwashers can consume more energy when tested with a load ofsoiled dishes, as compared to when testedwith a load of clean dishes. This indicates that the energy consumption ofa soil-sensing dishwasher, as measured in the currenttest method, does not likely representthe total per-cycle energy consumption ofa soilsensing dishwasher in householld use. Therefore, the measures derived from the total per-cycle energy consumption

- the energy factor and the estimated annual operating cost- do not represent a soil-sensing dishwasher in household use. Further, there is evidence that the representative average-use cycles per year is overstated. This means that the estimated annual operating cost ofa dishwasher

- whether soil-sensing or non-soilsensing

- is overestimated. Therefore, the information on the Energy Guide label is not representative and maybe misleading to consumers. The Energy Guide label on a soil-sensing dishwasher is particularly impacted as the estimated annual operating cost and the total per-cycle energy consumption are not representative ofhousehold use. The key questions in revising the test procedure for dishwashers to assure that soil-sensing dishwashers have energy factors not less than the minimum energy standard, and that the information onthe Energy Guide label is representative, are:


### 3- ",
1. How soiled are the dishes in the dishwashers ofU.S. households?,

- Quantity ofsoil?

- Type ofsoil? 2. How are the dishwashers loaded in U.S. households?

- Quantity ofdishware?

- Type ofdishware? 3. Howto reflect soiling in a modified energy consumption test method?, and 4. Howoften do U.S. households use a dishwasher? The following sections presentthe review and analysis ofa broad collection ofdata that lead to answers for these questions and offer an approach to incorporate the findings ofthe data in a revised energy consumptiontest procedure for dishwashers.

Data Sources This report is based on: 1) revh::w ofexisting industry and DOE dishwasher test standards; 2) review and analysis ofsurvey infonnatio 1 from eight individual sources including dishwasher and detergent manufacturers, energy and consumer interest groups, independent researchers, and government agencies; and 3) discussions with key personnel in industry, DOE, NIST, consumer groups and Arthur D. Little. The surveys fonn the core ofthe infonnation to address the key questions and to guide revisions to the testprocedure. They vary in size, breadth ofinfonnation, and quality of infonnationpertainingto consumers' dishwasher habits. More than halfofthe surveys are nationally representative, cumulatively representing over 20,000 respondents, while the others are regional in scope. The surveys present information collected between 1997 and 2001, however most ofthe surveys are from the 2000-2001 timeframe. Nationally representative means thatthe study populations ofthese surveys were selected to match or was judgedto distribute similarly to the U.S. Census profile ofhouseholds. The demographics considered to make this selection orjudgmentincluded: market size, age ofhousehold, type ofhousehold, household size, household income, type ofresidence, and ownership versus rental ofresidence. A key requirement ofthis report is to maintain the confidentiality ofthe industry survey sources. To this end no one industry source is referenced and the datapresented is an aggregation ofthe survey infonnation. However, Table :1 gives an overview ofeach survey's scope and size.
Table 1 - Overview ofscope and size ofsurveys Survey Scope Number of Breadth of Quality of Identifier Households Information Information Survey A Nationally Representative > 8,000 Wide High Survey B Nationally Representative > 11,000 Wide High Survey C Nationally Representative < 1,000 Wide High Survey 0 Regional > 1,000 Limited Moderate Survey E Regional < 250 Limited Low SurveyF Regional < 250 Moderate Moderate

4Survey G Nationally Representative < 500 Moderate Moderate Survey H Nationally Representative < 1,000 Moderate Moderate 1997 RECS Nationally Representative 5,900 Limited High The aggregation ofthe various survey data has required some regrouping ofthe survey results. The regrouping is necessitatedbecause each survey may have a different number ofcategories ordifferent categories for a particularhabit question. The following sections address howthe survey data addresses the data requirements outlined above, and how the survey data were analyzed to address those data requirements.

5Detailed Findings The findings ofthis review ofavailable survey data on U.S. households' dishwasher usage habits and characteristics and ofexisting dishwashertest standards showbroad support to address the key questions above and to make revisions to the energy consumption test procedure for dishwashers. The available surveys provide data on a number ofhabits and characteristics ofhouseholds with dishwashers, including:

• Households' pretreatment methods,

• Distribution ofhouseholds by level ofsoil in a dishwasher load,

• Quantitative amount ofsoil in a dishwasher load,

• Frequency ofhouseholds' usage ofa dishwasher,

• Distribution ofthe type ofdishware in H dish\'vasher load, and

• Size ofthe dishwasher load. Existing dishwasher cleaning performance test standards provide much ofthe data on critical elements for an energy consumptiontest procedure for soil·sensing dishwashers, including:

• Types ofsoil,

• "Worst case" amounts ofsoil,

• Application ofsoils to dishware,

• Types ofdishware, and

• Amount ofdishware. A majority oftherecommended revisions to the energy consumption test procedure drawprimarily from the survey data onthe following habits and characteristics ofhouseholds with dishwashers:

• Households' pretreatment methods,

• Distribution ofhouseholds by level ofsoil in a dishwasher loaq,

• Quantitative amounts ofsoil in a dishwasher load, and

• Frequency ofhouseholds' usage ofa dishwasher. Review ofexisting dishwashertest standards provided direction for test method elements that were either not covered or not widely covered by the surveys. These test method elements include:

• Types ofsoil, and

• Type ofdishware The findings below on the habits and characteristics ofconsumers with dishwashers, coupled with existingtest methods, build to address the key questions in revising the dishwasher test procedure.

6How soiled are the dishes in the dishwashers of U.S. households? This section covers survey data and test method information available to assess 1) the quantity ofsoil on dishware in U.S. households and 2) the type ofsoil onthe dishware. The quantity ofsoil is derived from dataonpretreatment methods and resultant soil levels on dishware, qualitative ranking ofsoil level, and assessment ofquantitative amounts associated with the qualitative ranking ofsoil level. Households' Pretreatment Methods Survey data from six ofthe eight sources (surveys A, C, E, F, G and H) provide information on households' pretreatment habits. Four ofthese surveys are nationally representative and cumulatively represent over 10,,000 U.S. households. All six ofthe survey sources presenttheir data in similar categories that make aggregation ofthe data direct and simple. Aggregating these surveys and weighting the responses in each category bythe total number ofrespondents indicates that more than 70%**ofU.~:.** households pretreat dishes with waterpriorto placingthem in the dishwasher. Figure 1 shows the aggngation ofthe surveys' responses to questions onpretreatmenthabits. The simple import ofthL.; finding is that currently the vast majority ofU.S. households' dishwasher loads are cleanerthan the.·) would be otherwise. Figure 1 - U.S. Households' Dishwasher Pretreatment Habits 80.0% ,..-----------------.-----.----.-.--------....-----------------.---..---.,

70.0% Over 70% of consumers pretreat dishes with water**beforE~** loading into dishwasher.

## -----------~-----------**~** 60.0% (" '\ .s::. U)

## ~ 50.0% is 

### :E**~** 40.0%**~** '0 .s::. 51 30.0% ::I o :I:

### ~ 20.0%

10.0%

0.0% Pre-rinse with Pre-wash, including Pre-soak the dish Scrape food water some scrubbing without water Pretreatment Method Removed large scraps Do nothing

7Distribution of Households by Level of Soil in a Dishwasher Load Four surveys (surveys A, C, D, and F) provide a combination ofqualitative and quantitative information onthe soil in a dishwasher load. The first consideration is the qualitative information on the level ofsoil in the dishwasher loads ofU.S. households. Surveys A and C are both large, nationally representative surveys that cumulatively represent over 9,000 U.S. households. Both surveys present very similar data on the qualitative level ofsoil on dishware inhouseholds' dishwasher loads. The larger ofthese two asked households to rate the overall level ofsoil in their dishwasher loads. The other ranked and categorized households' description ofthe overall level ofsoil in their dishwasher loads. Both ofthese two surveys distribute the level ofsoil in households' dishwasher loads inthree categories:

• Light level ofsoil,

• Medium level ofsoil, and

• Heavy level ofsoil. Surveys D and F are regional in scope and each present their data on the level \)fsoil in households' dishwasher loads in more than three categories. Both surveys asked households to rakthe overall level ofsoil in their dishwasher loads against the descriptions oftheir categories. Although each of the two surveys has more than three categories for the level ofsoil, the definitions oftheir categories clearly allow the data to be regrouped into the light, medium and heavy categories for soil level. Aggregating the two nationally representative sources (surveys A and C) and weighting the responses in each category by the total number ofrespondents yields a distribution ofhouseholds within these three categories that follows approximately 62%, 33% and 5% from light to heavy, as shownbelow in Figure 2. Including the two regional surveys in the aggregation changes the distribution only slightly to approximately 62%, 32%, and 6% from light to heavy. In either aggregation the result is nearly the same and consistent with the finding that most households rinse dishes before placing them in the dishwasher.

8Figure 2 - Distribution of U.S. Households by the Level ofSoil in Dishwasher Loads
70%

60%

I!! J! 50% III 

## ; s: III Q 40% s: :t:!**~** III 'tI 

## :g 30% GI III :::J 0 :J: iii 20% ::i

10%

0% 62%

Light 33%

Medium Soil Level Heavy

As it has bearing on determining amounts ofsoils representative ofeach ofthe three soil levels, it is important to note how these four surveys compare individually. Surveys A, C, and F each display very nearly the same distribution ofthe level ofsoil in households' dishwasher loads, which is essentially the distributionpresented in Figure 2. Survey D also shows a similartrend. At the light level ofsoil survey D is consistent with Figure 2 showing approximately 62% ofits respondents distribute in the light level ofsoil category. However, survey D departs from the other surveys at the medium and heavy levels ofsoil showing rather a distribution ofapproximately 21% at the medium level and 17% at the heavy level. The author(s) ofsurvey D noted concerns that some number oftheir respondents may not have been properly instructed on this question skewing their responses to heavier soil levels. Therefore, in the later sectionrelating amounts ofsoil to the soil levels, survey D is treated with complete discounting ofthe responses at the heavy level.
Types of Soil The available surveys provide only limited information on the types ofsoil on the dishware ofU.S. households. Similarly, broader industry experience has revealed the difficulty ofinventorying soil types onthe dishware ofU.S. households and representatively recreating those soils for the purpose oftesting. However, the Association ofHome Appliance Manufacturers (AHAM) has spent considerable time and effort to define the industry-recognized, 'worst case' cleaning performance test, ANSIIAHAM Standard DW-I-1992. DW-I precisely defines: 1) food soils that are representative ofthetypes of soils onthe dishware ofU.S. households; 2) amounts ofthose food soils, and 3) procedures to apply

9the food soils and to prepare the dishware for testing. D W-1 meets industry requirements for test repeatability. ANSIIAHAM Standard DW-l includes 13 food soils that are intended to be representative ofthe types offood soils onthe dishware ofU.S. households. These food soils are not intended to mirror exactly the food soils on the dishware ofU.S. households. Table 2 is an excerpt from ANSIIAHAM Standard DW-l that lists the food soils, the amounts ofthe food sufficient to soil a ten place table setting, and specific descriptions ofthe foods.
Table 2 - Soiling Ingredients from ANSI/AHAM Standard DW-1 Item Quantity Description Corn 6 teaspoons (30 ml) Cream style Eggs 4 (50 g) minimum weight Fresh, grade A, large Coffee Grounds 1**~** teaspoons (6 ml) Folgers, decaffeinated drip grind Round steak with all visible fat Ground Beef Mixture 5 teaspoons (25 ml) removed. Mix together 75% round steak with 25% kidney suet; grind together twice. Margarine 1 tablespoon (15 ml) Fleischmans corn oil (6 g offat per 14 l) serving) not whipped Milk 2/3 cup (160 ml) Carnation nofat dry Oatmeal 5 teaspoons (25 ml) Quaker Oats instant regular flavor (12 individual packages) Peanut Butter 2 

### 'V2 teaspoons (13 ml) JIF Creamy Potatoes 1**~~** teaspoons (65 ml) Hungry Jack instant mashed Preserves 1() teaspoons (50 ml) Smuckers red raspberry Salt 

### %teaspoon (1.25 ml) Morton iodized Tomato Juice 1 cup (240 ml) Campbell's Tomato Paste 12oz.can Contadina

10Figure 3 shows an example ofa place setting soiled with the foods specified in DW-1. However, the food soils in Figure 3 are not applied as precisely as specified in DW-l. Figure 3 - An Example ofa Place Setting Soiled with Food Soils from DW-1

Given the inherent difficulty ofengineering soil types and the fact that worst case soil types have already been defined by an industry standard, and that the currenttest method references part ofthat standard, 

### itis recommended in the best interest ofDOE and the industry to use the dishware soiling procedure inDW-l in a revised energy consumption test method for soil-sensing dishwashers. As described in the sectionbelow, surveys have probed consumers to define the quantity ofsoil on their dishes and often relate the quantity ofsoil in terms ofthe DW-1 standard.

11

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Quantitative Amount of Soil in a Dishwasher Load This section defines quantitative amounts ofsoil for each ofthe three soil levels that characterize the distribution ofsoil levels found in dishwasher loads ofU.S

.households. Surveys C, D, and F, cumulatively representing over 2,000 U.S. households, provide text and/or graphic descriptions to link their categories ofthe level ofsoil to the three soil levels

- Light, Medium, Heavy- and to quantitative amounts ofsoil for each level. Referencing ANSI!AHAM Standard DW-1 for the types ofsoil and, most importantly, the amounts ofsoil is essential in relating each ofthe three soil levels to an amount ofsoil. The relationship to the amounts ofsoil representative ofthe soil levels is derived differently for each survey, but for each survey the relationship is made intenns ofthe number ofplace settings in the DOEtest load that are soiled according to ANSIIAHAM Standard DW-l. The author(s) ofsurvey C make the relation from the extensive descriptions in their survey data to an associated amount ofsoil in tenns ofDW-l soiled place settings. For survey D the respondents directly make the link to an amount ofsoil in tenns ofDW··1 soiled place settings. For survey F, Arthur D. Little has made the link from the survey's description ofits soil categories to an amount ofsoil in terms ofDW-1 place settings. Table 3 shows the range ofthe survey data onrepresentative amounts ofsoil for each ofthe three soil levels. For each survey the amounts ofsoil are expressed in terms ofthe number ofplace settings in the DOE test load that are soiled according to ANSIIAHAM Standard DW-l.
Table 3 - Range of Survey Data on the Representative Amounts of Soil in the Three Soil Levels Soil Amounts in terms of Place Settings Soiled Per DW-1 Light Medium Heavy Survey C 1/2 2 5 Survey D 1-2 4-6 8 Survey F 1 4 8 Aggregating the survey data in Table 3 is not as straightforward as it was in previous sections. Only survey C is nationally representative while surveys D and F are regional. Although this difference alone is not necessarily a concern, this difference in combination with the differences in the representative amounts ofsoil between the nationally and regionally representative surveys presents a challenge. The depth, breadth, and national representation ofthe data available in survey C suggest that its representative amounts ofsoil for the three soil levels alone could be taken to represent U.S. households. However, including data from the narrower scopes ofsurveys D and F would yield more conservative, that is greater, representative amounts ofsoil for the three soil levels. Taking the more conservative path, surveys C, D, and F were aggregated to yield representative amounts ofsoil for each ofthe three soil levels. However, before aggregating these surveys the data from survey D needs to be treated carefully. As discussed previously, survey D shows the same distribution ofrespondents as in surveys C and F (also survey A) for the light level ofsoil, which is approximately 62%. At the medium and heavy levels ofsoil survey D departs from the other surveys showingrather a distribution ofapproximately 21% at the medium level and 17% at the heavy level. The author(s) ofsurvey D noted concerns that

12some number oftheir respondents were not properly instructed on this question and may have skewed their responses to the heavy soil level. The author(s) ofsurvey D intended that respondents select one ofseveral images that most closely represents the amount ofsoil typically found on each piece ofdishware in their dishwashers. Some respondents did not receive clarification onthis instruction and / or may have misinterpreted this instruction to mean "select one ofthe several images that most closely represents the total amount of soil on the dishware in their dishwashers." Certainly this misinterpretation would introduce an upward skewto any ofthe responses in survey D, notjustthose in the heavy soil level as the survey author(s) indicated. This means that its light soil level may be underestimated, its medium level may or may notbe impacted, and the heavy level may be overestimated. Given that some number ofrespondents may have taken this interpretation, there is cause to question survey D in general. However, for the purpose ofa conservative aggregation ofsurveys C, D, and F, survey D canbe included without great concern for overestimation, ifits responses in the heavy soil level are completely discounted. In the following aggregation survey D is included without its responses at the heavy soil level. Figure 4 showthe distribution ofresponses from surveys C, D (modified), and F on representative amounts ofsoil corresponding to the three soil levels

- Light, Medium, and Heavy. Calculatingthe weighted averages oftheresponses for each level ofsoil yields conservative values for the representative amounts ofsoil in each ofthe three soil levels found in the dishwashers ofU.S. households. Table 4 shows these results. Figure 4 - Distribution of Survey Respondents on Representative Amounts of Soil in Each ofthe Three Soil Levels
100% 

# 1

Gi 90% {
> f j 80% 

## + ·0 r en I .s::. 70% 1 u

60%

# 1 CII w .5 J!l c III "0 c 50% 

### 8. 1/1**~** 

# F 40%

::l 30% en 0


# .. c 20% III**~** III II.. 10%

0% 1/2 2 2 4 6 5 8 Number of Place Settings inthe DOE Test Load Soiled According to DW-1

13Table 4 - Representative Amounts of Soil in Each ofthe Three Soil Levels Found in Dishwashers of U.S. households

L Soil Amounts in terms ofPlace Settings Soiled Per DW-1 Light Medium Heavy 

# I Weighted Average 1 3 6

14How are the dishwashers loaded in U.S. households? This section considers the information available in surveys A and C to understand how many dishes and whattype ofdishes shouldbe inthe test load(s) ofDOE's energy consumptiontest procedure. Quantity of dishware The available survey information clearly indicates that in the vast majority ofhouseholds (> 80%) dishwashers are run at full capacity. Given the directness ofthis finding, it is recommended that the eightplace settings test load called for in the existing test method should be retained and applied to any revisions to the test method for soil-sensing dishwashers. Itis interesting to note the implication ofthis finding in conjunction with the finding on the frequency ofuse ofa dishwasher found in a later section ofthis report. As most households only operate a dishwash;:r once it is full, and dishwashers are run about once every other day, then the dishware, pretreatec.' ancl r,ot, is accumulating overtwo days. The further implication is that some portion, probably half,**O)~the** dishware in the load, pretreated and not, is air-drying for about a day. The dishwasher bdustry is aware ofthe implication that dishware with varying amounts ofsoil is airdrying prior to mIming a cycle and that this can affect the cleaning performance ofa dishwasher. ANSI!AHAM Standard D W-1 currently calls for a two hours ofair-drying for soiled dishware prior to running a test load. AHAM, its members, and other interested groups are reviewing the need to revise the air-drying specification. Itis recommended that any revisions to the air-drying specification inANSI!AHAM Standard DW-1 should be automatically included in the revised test method for soil-sensing dishwashers as it is an integral part ofa soiling procedure dishware. Type of dishware The available survey information indicates, as might be expected, that there is a wide variety of dishware used in U.S. households. However, survey A offers some information on the material type ofdishware. Survey A indicates that for more than halfofthe households surveyed, plastic dishware makes up a quarter or more ofthe dishwasher loads. The impact ofa portion ofthe test load being made up ofplastic dishware is unknown. However, any impact is likely to be ofsecondary importance to implementing a soil-based test method for soilsensing dishwashers. Therefore, it is recommended that a revised test method for soil-sensing dishwashers use the uniform set ofceramic dishware and glassware referenced in the current test method. As a future effortthe impact ofplastic dishware may be assessed and considered in later revisions to the test method.

15

i IHow to reflect soiling in a modified energy consumption test method? This sectionpresents an approach to modify the energy consumptiontestprocedure for dishwashers to consider soil-sensing dishwashers. The proposed approach follows directly from the above findings. Proposed Energy Consumption Test Method This proposed revision to the energy consumptiontest method for dishwashers applies only to soilsensing dishwashers. The revision would create two paths in the test method. One path for non-soilsensing dishwashers would follow the existing test method. The otherpath for soil-sensing dishwashers would follow the outline belowfor a revised test method. The revised test method. requires three energy consumptiontests using different numbers ofsoiled dishware. To cover**th~** distribution ofsoil levels in the dishwasher loads ofU.S. households, the energy consumption ofseil-sensing dishwashers needs to be measured at each ofthree soil levels

- Light, Medium, and Heavy- creating a three-point test method. The amount ofsoil at each ofthe soil levels is defined by the number ofplace settings out ofthe eight place settings in the existing test load that are soiled in accordance whh ANSI!AHAM Standard DW-1. The number ofsoiled place settings in the test load at eacr} \)fthe soil levels is shown in the test schedule in Table 5.
Table 5 - Test Schedule for Soil-Sensing Dishwashers Soiled Place Settings Clean Place Settings Test Number Soil Level per AHAM Standard perAHAM Standard Total Place Settings DW-1 DW-1 1 Light 1 7 

### 8 2 Medium 

### 3 5 

### 8 3 Heavy 6 2 

### 8 Note that the six serving pieces called for in the existing test method would be included clean. The energy consumption for each ofthe three tests would be measured and calculated in the same way as the existing test method. However, the energy factor for a soil-sensing dishwasher would be based on a weighted average ofthe three energy consumption tests. The weighting factors are the percentages for the distribution ofU.S. households in the three soil level categories

- 62% Light level ofsoil, 33% Medium, and 5% Heavy (see Figure 2). Incorporating the weighting factors with the energy consumed in each test yields an energy factor for soil-sensing dishwashers as defined in Equation 1. Equation 1 - Energy Factorfor Soil-Sensing Dishwashers
EFsoll-sensing

# =1/«.62*Test#1 Energy)+(.33*Test#2 Energy)+(.05*Test #3 Energy))

16How often do U.S. households use a dishwasher?
Frequency of households' usage ofa dishwasher Surveys from six ofthe eight sources present information on the frequency ofhouseholds' use ofa dishwasher. Five ofthe six surveys (surveys A, B, G, H, and 1997 RECS) are nationally representative and cumulatively represent over 20,000 U.S. households. One ofthese five surveys is the Energy Information Administration's 1997 Residential Energy Consumption Survey (1997 RECS). The 1997 RECS data onthe usage ofa dishwasher, as shown in Figure 5, indicatethat more than halfofU.S. households with a dishwasher use it less than 4 times per week. Therefore, the number ofrepresentative average-use cycles peryear for a dishwasher should be inthe vicinity of208 cycles peryear. Although this is far fewer**cycle~s** per year**~han** the 264 cycles per year recommended in an interim rulemaking on dishwashers, it is not**inco.'1~;istent** with the steady decrease overthe past 20 years in the average-use cycles for a dishwas.'1Ier. ElA's data are far more recent than the data available for the interim rulemaking thatrecommends 264 cycles peryear. The 264 cyclesperyear in the interim rulemaking is based on an average ofdata gcthered between 1985 and 1995. Figure 5 - 1997 RECS-Usage of a Dishwasher 60.0% r········..·····•·····························
....·······...........•........•....
-•...................................................•.•....................................................................................................................................................................................................•.......................................................................................,



### ... ell s:. III 50.0%

; 40.0% s:. III 

### o C\I 

# :e**~** 30.0% III 

## " 15 s:.

### ~**~** 20.0% en ::i

10.0%

0.0% +---- Less Than 4 Times 4 to 6 Times At Least Once Each Day However, calculating an average value for usage ofa dishwasher from the RECS data is not straightforward. To determine an average requires definition ofa single value for eachcategory that is to be weighted by the percentage ofresponses inthat category. The categories, "less than 4 times" and "at least once each day", do not define a single value and therefore, make determining an average somewhat arbitrary.

17The issue in determining an average is not limited to the RECS data. Several ofthe other surveys share the problem ofdefining a single value for a category, but to a much less extent than the RECS data. Generally the other surveys minimize this issue by including more categories, by better distributing categories, and by having more bounded categories. To analyze the frequency ofuse data a consistent approach was used to estimate values for the surveys' categories. A low value, an average value, and a high value were defined for each category found in the surveys. Forbounded categories, such as "3-4 times per week", the low value was 3, the average value was 3.5, and the high value was 4. Forupper bounded categories, such as "once a month or less", the low value was taken as 1per 6 weeks, the average value was taken as 1per 5 weeks, and the high value was taken as 1per4 weeks. For lower bounded categories, such as "at least once per day", the low value was taken as 7 per week, the average value was taken as 8 per week, and the high value was taken as 9 per week. The five nationally representative surveys, including the RECS data, were analyzed in this way. Table 6 shows the range ofaverage-use cycles**caicula~ed** using the low, average, and high values for the categories in each survey. On inspection ofTlble 6, it is clear that the surveys' data on average frequency ofuse falls roughly in two groups - less than L'06 cycles per year and greater than 206 cycles per year. Table 6 - Range ofAverage-Use Cycles I Year for a**Di!ihwa~.her** Range ofAverage-Use Cycles IYear for a Dishwasher Low Category Values Average Category High Category Values Values Survey A 

### 162 181 201 Survey B 

### 153 191 230 Survey G 

### 155 189 224 Survey H 

### 225 225 226 1997 RECS 

### 207 245 282 Average of 180 206 

### 233 Averages

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# -------------------------------

# !Another approachto reduce the surveys' data to a value for the representative average-use cycles per year is to considerthe distribution ofresponses for the categories ofthe five nationally representative surveys as shown in Figure 6. lin aggregate the five nationally representative surveys indicate that halfofU.S. households with dishwashers use their dishwashers less than 170 times peryear. Again calculating an average ofthese categories requires definition ofa single value for each category. By applying the average value for each category, as in the above discussion, to the distribution in Figure 6 an average weighted bythe number ofrespondents in the five nationally representative surveys can be calculated. This calculation yields a weighted average of200 cycles peryear. Figure 6 - Distribution of Frequency of Households' Use of a Dishwasher

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- Median: half ofthe responses are at 3.£8/week or less I.e. -170 cycles per year or le:ls

- Average: in aggregate, the average is 3.86 CYCleS per week or -200 cycles per year.

9 

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The previous discussions on the frequency ofuse ofdishwashers in U.S. households suggest that the representative average-use cycles per year for a dishwasher should be at least 200. Additional data from the dishwasher detergent industry is being sought to refine further the number for the representative average-use cycles peryear. This additional data is anticipated for late December 2001 or early January 2002. Without regard for this additional data it is clearthat a revised number for the representative average-use cycles peryear should be substantially less thanthe 264 inthe interim rulemaking, butnot less than 200 cycles peryear.

19Recommendations The following is a summary ofArthur D. Little's recommendations onrevisions to the Department of Energy's testprocedures for measures ofenergy and water consumption and their "Uniform Test Method for Measuring Energy Consumption ofDishwashers". Arthur D. Little's recommendations onrevisions to the testprocedure include:

• Creating a separate path in the test method for soil-sensing dishwashers and adopting the three pointtest method for soil-sensing dishwashers outlined above, and

• Reducing the average-use cycles peryear for dishwashers into the range of200 to 233 cyclesperyear. In addition to these revisions to the test procedure, there are several other recommendations for future actions to capture greater efficiency benefits with dishwashers and to maint(l.in the test procedure for dishwashers:

• Assessing the energy impact ofpretreating dishes and the energy saviDis opportunities of greater utilization ofdishwashers,

• Supporting industry efforts to update and maintain the ANSI!AHAM Standard DW-1,

• Assessing the energy impact ofplastic dishware in the test load, and

• Monitoring and updating the distribution ofhouseholds with dishwashers by the level of soil inthe load through a follow-up assessment ofhouseholds' dishwasher usage habits and characteristics.

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