## Review of Survey

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- u 

# E1JILDING
•#4 tC; I ur 

## Data to Support Revisions to DOE’s Dishwasher Test Procedure

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

Date: November 29, 2001

Arthur D. Little, Inc. Acorn Park Cambridge, MA 02140.3

Executive Summary 

### To support revisions to the Department ofEnergy’s testprocedures for measures ofenergy and water consumption in dishwashers various survey data on consumers’ dishwasherusage habits were collected from a number ofsources including several dishwashermanufacturers, detergent manufacturers, energy and consumerinterest groups, independentresearchers, and government agencies. The fmdings ofthe review ofavailable data on consumers’ dishwasherusage habits showbroad supportto defme:

• Consumers’ pretreatmentmethods,

• Distribution ofhouseholds by the level ofsoil in a dishwasherload,
• Quantitative amount ofsoil on the dishware, and
• Frequency ofhouseholds’ use ofa dishwasher. Drawing from these survey fmdings, the existing test method for dishwashers, and ANSIJAHAM 

### Standard DW- 1, a weighted, three-point testmethodusing differentnumbers ofsoiled dishware is recommended to measure the energy consumption ofsoil-sensing dishwashers. It is further recommendedthatthe number ofaverage-use cycles per yearbe reducedto 203.

Background 

### The Department ofEnergy’s Dishwasher Test Procedure is in the process ofbeing revised. The need to revise the testprocedure is driven by the development ofadvanced soil-sensing dishwashers. The introduction inthe mid- 1990’s ofadvanced dishwashers equipped withthe ability to sense the soil level in the dishwasher and in response to adjustthe wash cycle created a challenge to the Dishwasher Test Procedure. The currenttestprocedure, designed for fixed cycle dishwashers, measures energy consumption using a load ofclean dishes. It has been well demonstratedthat soilsensing dishwashers yield lower energy consumption when tested with the clean load ofdishes, as comparedto when tested with soiled dishes. Therefore, current energy consumptionresults for soil sensing dishwashers are not representative ofthe actual energy consumption ofsoil-sensing dishwashers in use by consumers. This inaccuracy, created by the evolution oftechnology, necessitates revision ofthe DishwasherTest Procedure. In addition to technology-driven change, consumers’ usage ofdishwashers has also changed. The most notable change in dishwasherusage 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 ofdishwasherusage has decreased significantly.

2Overview ofCurrent Dishwasher Test Procedure The Department ofEnergy’s testprocedures formeasures ofenergy and water consumption (10 CFR 430.23(c)) call out measures forthe 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 CFR 430 Subpt. B, App. C). The current test methoduses a test load ofclean dishes. The test load consists of8 place settings ofdishware plus 

### six serving pieces as specified in the industry-recognized standard, AHAM Standard DW- 1. The total per-cycle energy consumption ofa dishwasheris based on the energy consumption measured during this test with a load ofclean dishes. Dishwashers must meet or exceed aminimum energy factor (10 CFR 430.32

### cf)). The energy factor for dishwashers is the reciprocal ofthe total per-cycle energy consumption. Standard dishwashers (currently equal to or greater than 22” in exterior width) must have an energy factor not less than 0.46 cycles/kWh. Compact dishwashers (currently, less than 22” in exterior width) musthave an energy factor not less than 0.62 cycles/kWh. 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 dishwasheris based on the 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 comparedto when tested with a load of clean dishes. 

### This indicates that the energy consumption ofa soil-sensing dishwasher, as measured in the current test method, does not likely representthe total per-cycle energy consumption ofa soilsensing dishwasher in householduse. Therefore, the measures derived fromthe 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-soil sensing

— is overestimated. Therefore, the information on the Energy Guide label is not representative and may be 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 ofhouseholduse. The key questions to understand in defining an energy consumption test for soil-sensing dishwashers, assuring that soil-sensing dishwashers have energy factors not less than the minimum energy standard, and assuring that the information on the Energy Guide label is representative, are: 1. How soiled are the dishes in the dishwashers ofU.S. households?,

— Quantity ofsoil?

— Type ofsoil?

32. How are the dishwashers loaded in U.S. households?

— Quantity ofdishware?

— Type ofdishware? 3. How to reflect that soiling in a modified energy consumptiontest method?, and 4. How often do U.S. households use a dishwasher? The following sections presentthe review and analysis ofa broad collection ofdatathat lead to answers forthese questions and offer an approach to incorporate the fmdings ofthe data in a revised energy consumption test procedure for dishwashers.
Data Sources This report is based on: 1) review ofexisting industry and DOE dishwasher test standards; 2) review and analysis ofsurvey information from eight individual sources including dishwasher and detergent manufacturers, energy and consumer interest groups, independentresearchers, and government agencies; and 3) discussions with key personnel in industry, DOE, NIST, consumer groups and Arthur D. Little. The surveys form the core ofthe information to address the key questions and to guide revisions to the testprocedure. They vary in size, breadth ofinformation, and quality of informationpertaining to consumers’ dishwasherhabits. 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, howevermost ofthe surveys are fromthe 2000-2001 timeframe. Nationally representative means that the study populations ofthese surveys were selected to match or was judgedto distribute similarlyto the U.S. Census profile ofhouseholds. The demographics considered to make this selection orjudgment included: 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 information. However, Table 1 gives an overview ofeach survey’s scope and size. Table I

— Overview ofscope and size ofsurveys Survey Number of Breadth of Quality of

. Scope Identifier Households Information Information Survey A Nationally Representative > 8,000 Wide High Survey B Nationally Representative > 6,000 Wide High Survey C Nationally Representative < 1,000 Wide High Survey D Regional > 1,000 Limited Moderate Survey E Regional < 250 Limited Low Survey F Regional < 250 Moderate Moderate Survey G Nationally Representative < 500 Moderate Moderate Survey H Nationally Representative < 1,000 Moderate Moderate

41997 RECS Nationally Representative 5,900 Limited High The aggregation ofthe various survey datahas required some regrouping ofthe survey results. The regrouping is necessitated because each survey may have a different number ofcategories or different categories for aparticularhabit question. The following sections address how the survey data addresses the datarequirements outline above, and how the survey data was analyzed to address those data requirements.

5Detailed Findings 

### The fmdmgs ofthis review ofavailable survey data on U.S. households’ dishwasherusage habits and characteristics and ofexisting dishwashertest standards show broad supportto 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 a dishwasher load, and

• Size ofthe dishwasherload. Existing dishwasher cleaning performance test standards provide much ofthe data on critical elements for an energy consumption testprocedure for soil-sensing dishwashers, including:

• Types ofsoil,

• “Worst case” amounts ofsoil,

• Application ofsoils to dishware,

• Types ofdishware, and

• Amount ofdishware. A majority ofthe recommended revisions to the energy consumption testprocedure draw primarily fromthe survey data on the following habits and characteristics ofhouseholds with dishwashers:



### • Households’ pretreatment methods,

• Distribution ofhouseholds by level ofsoil in a dishwasher load,

• Quantitative amounts ofsoil in a dishwasher load, and

• Frequency ofhouseholds’ usage ofa dishwasher. Review ofexisting dishwashertest standards provided direction fortest method elements that were eithernot covered ornot widely coveredby the surveys. These test method elements include:

• Types ofsoil, and

• Type ofdishware The fmdings below on the habits and characteristics ofconsumers with dishwashers, coupled with existing test methods, buildto address the key questions in revising the dishwashertest procedure.

6How soiled are the dishes in the dishwashers of U.S. households? This section covers survey data 

### and test method infonnation available to assess 1) the quantity ofsoil on dishware in U.S. households and 2) the 

### type ofsoil on the dishware. The quantity ofsoil is derived from data on pretreatment 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’ pretreatmenthabits. Four ofthese surveys are nationally representative 

### and cumulatively represent over 10,000 U.S. households. All six ofthe survey sources present their data in similar categories that make aggregation ofthe data direct and simple. Aggregating these surveys and weighting the responses in each category by the total number ofrespondents indicates that more than 70% ofU.S. households pretreats dishes with waterpriorto placing them in the dishwasher. Figure 1 shows the aggregation ofthe surveys’ responses to questions on pretreatment habits. The simple 

### import ofthis finding is that currently the vast majority ofU.S. households’ dishwasher loads are cleaner than they would be otherwise. Ficiure I

— U.S. Households’ Dishwasher Pretreatment Habits 50.0%
70.0%

Ca a, U, CU 5o% b 40.0% U, 0 30.0% 0
D 10.0%
00%

Pretreatment Method 60.0%

20.0%

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

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 on the 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 in households’ dishwasher loads. The larger ofthese two 

### asked households to rate the overall level ofsoil in their dishwasher loads. The otherranked and categorized households’ description ofthe overall level ofsoil in their dishwasherloads. 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 eachpresent their data on the level ofsoil in households’ dishwasher loads in more than three categories. Both surveys asked households to rate the overall level ofsoil in their dishwasher loads against the descriptions 

### oftheir categories. Although each of the two 

### surveys has more than three categories forthe level ofsoil, the defmitions 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 and weightingthe 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 lightto heavy, as shown 

### below in the Figure 2. Including the 

### two regional surveys inthe aggregationchanges the distribution only slightly to approximately 62%, 32%, 

### and 6% from light to heavy. In either aggregationthe result is nearlythe same and consistent withthe fmding that mosthouseholds rinse dishes before placing them in the dishwasher.

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

60%

U, .2 50% U, U, U, 40%

U, _______________

30% U, U, z 0 u 20% D 10%

0% Medium Heavy Soil Level 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 individually each display very nearly the same distribution ofthe level ofsoil in households’ dishwasher loads, which is essentially the distributionpresented in Figure 2. Survey D departs substantially from this distribution showing rather a distribution ofapproximately 62%, 21%, and 17% from light to heavy. The author(s) ofsurvey D noted concerns that some number oftheir respondents may not have been properly instructed on this question skewing their response to the heavy soil level. Therefore, in the later section relating amounts ofsoil to the soil levels, survey D is treated with substantial discounting ofthe response in the heavy soil 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 on the dishware ofU.S. households and representativelyrecreating those soils forthe purpose oftesting. However, the Association ofHome Appliance Manufacturers (AHAM) has spent considerable time and effort to defme the industry-recognized, ‘worst case’ cleaning performance test, ANSL’AHAM Standard DW-1-1992. DW-1 precisely defmes: 1) food soils that are representative ofthe types of soils on the dishware ofU.S. households; 2) amounts ofthose food soils, and 3) procedures to apply the food soils and to prepare the dishware for testing. DW-1 meets industry requirements fortest repeatability. 62%

33%

Light 5%

9ANSIJAHAM Standard DW-1 includes 13 food soils that are intended to be representative ofthe types offood soils on the dishware ofU.S. households. These foods soils are not intended to mirror exactly the food soils on the dishware ofU.S. households. Table 2 is an excerpt from ANSIJAHAM Standard DW-1 that lists the food soils, the amounts ofthe food sufficient to soil aten place table setting, and specific descriptions ofthe foods. Table 2

— Soiling Ingredients from ANSIIAHAM 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 1⁄4 teaspoons (6 ml) Folgers, decaffeinated drip grind Round steak with all visible fat removed. Mix together 75% round Ground Beef Mixture 5 teaspoons (25 ml) steak with 25% kidney suet; grind togethertwice. Fleischmans corn oil (6 g offat per 14 Margarine 1 tablespoon (15 ml) g serving) not whipped Milk 2/3 cup (160 ml) Carnation nofat dry Quaker Oats instant regular flavor (12 Oatmeal 5 teaspoons (25 ml) individual packages) Peanut Butter 2 1/2 teaspoons (13 ml) JIF Creamy Potatoes 13 teaspoons (65 ml) Hungry Jack instant mashed Preserves 10 teaspoons (50 ml) Smuckers red raspberry Salt 1/4 teaspoon (1.25 ml) Morton iodized Tomato Juice 1 cup (240 ml) Campbell’s Tomato Paste 12 oz.can Contadina

10Figure 3 shows an example ofaplace setting soiled with the foods specified in DW-l. However, the food soils in Figure 1 are not applied as precisely as specified in DW-l. Figure 3

— An example of a Place Setting Soiled with Food Soils from DW-1

Given the inherent difficulty ofengineering soil types and the fact that a worst case soil types has already been defmedby an industry standard, and that the current testmethod references part ofthat standard, it is recommended in the best interst ofDOE andthe industry to use the dishware soiling procedure in DW-1 in arevised energy consumption test method for soil-sensing dishwashers. As described in the section below, surveys have probed consumers to defme the quantity ofsoil on their dishes and often relate the quantity ofsoil in terms ofthe DW-1 standard.



### 11Quantitative Amount ofSoil 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, cumulativelyrepresenting over 2,000 U.S. households, provide text and/or graphic descriptions to linktheir categories ofthe level ofsoil to the three soil levels

— Light, Medium, Heavy- andto quantitative amounts ofsoil for each level. Referencing ANSJJAHAM Standard DW-1 forthe 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 interms ofthe number ofplace settings in the DOE test load that are soiled according to ANSIJAHAM Standard DW-1. The author(s) ofsurvey C make the relation from the extensive descriptions in their survey datato an associated amount ofsoil in terms ofDW-1 soiledplace settings. For survey D the respondents directly make the linkto an amount ofsoil in terms ofDW-l soiledplace 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 on representative 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 ANSI/AHAM Standard DW-l. Table 3

— Range ofSurvey Data on the Representative Amounts ofSoil in the Three Soil Levels Soil Amounts in terms of Place Settings Soiled Per DW-1

Light Medium Heavy SurveyC %ofl 2 4-5

• Survey D 1-2 4-6 6-8

. SurveyF 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 national andregionally representative surveys presents a challenge. The depth, breadth, and national representation ofthe data available in survey C suggest that its representative amounts ofsoil forthe three soil levels alone could be taken to represent U.S. households. However, including data fromthe 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 corresponding to the heaviest amount ofsoil needed to be discounted. As noted earlier, the author(s) ofsurvey D raised accuracy concerns and cast suspicion on some number of their responses that may have skewedto greater amounts ofsoil due to lack ofproper instruction.

12The data from survey D was discounted in the following way to address this concern. The percentage ofresponses in its heaviest soil category was reduced from 17% to 5% ofits respondents making it consistent with all ofthe other surveys. The responses displaced by this reduction were discarded, as any attempt to redistribute them to lighter soil categories in survey D would only introduce uncertainty. Figure 4 show the distribution ofresponses from surveys C, D (modified), and F on representative amounts ofsoil corresponding to the three soil levels

—Light, Medium, and Heavy. Calculating the weighted averages ofthe responses 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 ofSurvey Respondents on Representative Amounts of Soil in Each ofthe Three Soil Levels 100%

—

Light Soil Level

- 1 Soiled Place

Table 4— Representative Amounts of Soil in Each ofthe Three Soil Levels Found in Dishwashers of U.S. households Soil Amounts in terms of Place Settings Soiled Per DW-1 Weighted Average 1 3 6 Medium Soil Level

- 3 Soiled Place Settings Heavy Soil Level

- 6 Soiled Place Settings a -J 0 Co U a w C C C a C 0 a. ‘5 a a Cl, I 0 C a C) a a. 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 1/2 1 2 2 4 6 Number of Place Settings in the DOE Test Load Soiled According to DW-1 5 8

Light Medium Heavy

13How are the dishwashers loaded in U.S. households? This section considers the information available in 

### surveys A and C to 

### understandhow many dishes and whattype ofdishes should be in the test load(s) ofDOE’ s energy consumption testprocedure. Quantity ofdishware The available survey information clearly indicates that in the vast majority ofhouseholds (> 80%) dishwashers are run at full capacity. Given the directness ofthis fmding, it is recommended thatthe eightplace settings test load called forin the existing testmethod shouldbe retained and appliedto any revisions to the test method for soil-sensing dishwashers. It is interesting to note the implication ofthis fmding in conjunction withthe fmding on the frequency ofuse ofa dishwasher found in a later section ofthis report. As most households only operate a dishwasher once it is full, and dishwashers are run about once every other day, then the dishware, pretreated and not, is accumulating overtwo days. The further implication is that some portion, probably half, ofthe dishware in the load, pretreated and not, is air-drying for about a day. The dishwasherindustry is aware ofthe implication that dishware with varying amounts ofsoil is airdrying priorto running a cycle and that this can affect the cleaning performance ofa dishwasher. ANSIJAHAM Standard DW-l currently calls for a two hours ofair-drying for soiled dishware prior to running a test load. AHAM, its members, and others interested groups are reviewing the needto revise the air-drying specification. It is recommendedthat any revisions to the air-drying specification in ANSI/AHAM Standard DW-1 shouldbe automatically included in the revised test method for soil-sensing dishwashers as it is an integral part ofa soiling procedure dishware. Type ofdishware The available survey information indicates, as mightbe expected, thatthere 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 thanhalfofthe households surveyedplastic dishware makes up a quarter or more ofthe dishwasher loads. The impact ofaportion ofthe test loadbeing made up ofplastic dishware is unknown. However, any impact is likely to be ofsecondary importance to implementing a soil-based test method for soil sensing dishwashers. Therefore, it is recommended that a revised testmethod for soil-sensing dishwashers use the uniform set ofceramic dishware and glassware referenced in the current test method. As a future effort the impact ofplastic dishware may be assessed and considered in later revisions to the test method.



### 14How to reflect that soiling in a modified energy consumption test method? This section presents an approach to modify the energy consumption testprocedure for dishwashers to consider soil-sensing dishwashers. The proposed approach follows directly fromthe above findings. Proposed Energy Consumption Test Method This proposed revision to the energy consumption test method for dishwashers applies only to soilsensing dishwashers. The revision would create two paths in the test method. One path fornon-soilsensing dishwashers would follow the existing test method. The otherpath for soil-sensing dishwashers would follow the outline below for a revisedtest method. The revised test method requires three energy consumption tests using different numbers ofsoiled dishware. To coverthe distribution ofsoil levels in the dishwasher loads ofU.S. households, the energy consumption ofsoil-sensing dishwashers needs to be measured at each ofthree soil levels

— Light, Medium, and Heavy- creating athree-point testmethod. The amount ofsoil at each ofthe soil levels is defmed by the number ofplace settings out ofthe eight place settings in the existing test load that are soiled in accordance with ANSIIAHAM Standard DW- 1. The number ofsoiled place settings in the test load at each ofthe 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 Soil Level per AHAM Standard per AHAM Standard Total Place Settings Number 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 dishwasherwouldbe based on a weighted average ofthe three energy consumption tests. The weighting factors are the percentages forthe 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 eachtest yields an energy factor for soil-sensing dishwashers as defmed in Equation 1. Equation I

— Energy Factor for Soil-Sensing Dishwashers EFsoii.sensing = 1I((.62*Test #1 Energy)+(.33*Test #2 Energy)+(.05*Test #3 Energy))

15How often do U.S. households use a dishwasher? Frequency ofhouseholds’ usage of a dishwasher Surveys from six ofthe eight sources present information on the frequency ofhouseholds’ use ofa dishwasher. Five ofthe six surveys 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 on the usage ofa dishwasher, as shown in Figure 

### 5, indicates that more than halfofU.S. households with a dishwasheruse it less than 4 times perweek. Therefore, the number ofrepresentative average use cycles per year for a dishwasher shouldbe in the vicinity of208 cycles per year. Although this is far fewer cycles per yearthanthe 264 cycles peryearrecommended in an interim rulemaking on dishwashers, it is not inconsistent with the steady decrease overthe past 20 years in the average use cycles for a dishwasher. ETA’s data is farmore recent than the data available forthe interim rulemaking that recommends 264 cycles per year. The 264 cycles per year in the interim rulemaking is based on an average ofdata gathered between 1985 and 

### 1995. Figure 5— 1997 RECS-Usage of a Dishwasher 60.0%

50.0% a) 40.0%

30.0% U, 0 0 U) 20.0% 05
10.0%

0.0% Less Than 4 Times 4 to 6 Times At Least Once Each Day <1:5;’ <5> However, calculating an average value forusage ofa dishwasher from the RECS data is not straightforward. To determine an average requires definition ofa single value for each category that is to be weighted by the percentage ofresponses in that category. The categories, “less than 4 times” and “at least once each day”, do not defme a single value and therefore, make determining an average somewhat arbitrary.


### 16The 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. Generallythe 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 define an average value for categories. A low value, an average value, and a high value were defmed 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. Forupperbounded categories, such as “once a month or less”, the low value was taken as 1 per 6 weeks, the average value was taken as 1 per 5 weeks, and the high value was taken as 1 per 4 weeks. For lowerbounded 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 and treated in aggregate. Table 6 shows the range ofaverage-use cycles calculated using the low, average, and high values for each category. Table 6 also shows the medians and the means forthose ranges. Table 6— Range ofAverage-Use Cycles I Yearfor a Dishwasher Range of Average-Use Cycles Near for a Dishwasher Lowest Highest M Median of AveraQe Averaqe ean Averaqes Low Category Values 153 225 181 162 Average Category Values 181 245 206 191 High Category Values 201 282 232 226

17

### S S


## /€ to S(Y2 

# riioC - Median: half ofthe responses are at 3.53/week or less I.e. —184 cycles per year or less.

- Average: in aggregate, the average is 3.91 cycles per week or —203 cycles per vor 

### Taking the five nationally representative surveys in aggregate, the distribution ofresponses forthe categories ofthese surveys is shown in Figure 6. Calculating a weighted average ofthese categories a representative average-use ofa dishwasher of203 cycles per year. Fiqure 6

— Distribution of Freciuencv of Households’ Use of a Dishwasher 16%
14%
(0 12% c0

0’ (0 10i
8%
6%
4%
2%
0% 

# [1
n ii 

### fl I I I



### 18Recommendations The following is a summary ofArthur D. Little’s recommendations on revisions to the Department of Energy’s testprocedures formeasures ofenergy and water consumption and their “Uniform Test Method for Measuring Energy Consumption ofDishwashers”. Arthur D. Little’s recommendations on revisions to the testprocedure include:

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

• Reducing the average-use cycles per year for dishwashers to 203 cycles peryear. In additionto these revisions to the testprocedure, there are several otherrecommendations for future actions to capture greater efficiencybenefits with dishwashers andto maintain the testprocedure for dishwashers:

• Assessing the energy impact ofpretreating dishes and the energy saving opportunities of greaterutilization ofdishwashers,

• Supporting industry efforts to update and maintain the ANSIJAHAM Standard DW-l,

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

• Monitoring and updating the distribution ofhouseholds with dishwashers by the level of soil in the load through a follow-up assessment ofhouseholds’ dishwasherusage habits and characteristics.



### 19