Reference Publications AlllOS fiTTTE

NBSIR 80-2136

Energy Consumption and Usage

Characteristics From Field

Measurements of Residential

Dishwashers, Clothes Washers and

Clothes Dryers

Yui-May L Chang

Richard A. Grot

Building Equipment Division

Center for Building Technology

National Engineering Laboratory

U S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

October 1980

.QQ— DEPARTMENT OF COMMERCE

100 ONAL BUREAU OF STANDARDS

.U56

80-2136

1980

National Bureau of Standards

Library, E-01 AdmifU Bldg.

APR 1

NBSIR 80-2136

ENERGY CONSUMPTION AND USAGE

CHARACTERISTICS FROM FIELD

MEASUREMENTS OF RESIDENTIAL

DISHWASHERS, CLOTHES WASHERS AND

CLOTHES DRYERS

Yui-May L. Chang

Richard A. Grot

Building Equipment Division

Center for Building Technology

National Engineering Laboratory

U.S. Department of Commerce

National Bureau of Standards

Washington, DC 20234

October 1980

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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ABSTRACT

The measured energy consumption and usage characteristics for household

dishwashers, clothes washers, and clothes dryers for ten townhouses at

Twin Rivers, N.J. are presented. Whenever the dishwashers and/or clothes

washers were in use, the energy consumption, water consumption, frequency of

usage, and water temperature were measured by a data acquisition system. The

energy requirement for heating hot water could be established from the water

heater's characteristic in a previous related report (NBSIR 78-1496). The

electrical energy of electric clothes dryers and the gas consumption of gas

clothes dryers were measured, as well as their frequency and duration of use,

and exhaust temperature. Typical household usage patterns of these major

appliances are also included.

It was found that, in general, the electrical energy required to operate

dishwashers and clothes washers is about one tenth of the energy consumption

for heating hot water. Cold water usage is about three times the hot water

usage for each load of laundry. The energy loss from a pilot light burner

of a gas dryer is about 50 percent of the total gas consumption of that dryer

As far as habits are concerned, the average family utilizes the dishwasher

every other day and the laundry about five loads a week.

Key Words; Clothes dryer usage chacteristics ; clothes washer usage character

istlc; data profiles; dishwasher usage characteristic; energy

consumption; field measurements; usage patterns; water consumption.

i iii
UNITS OF MEASURE AND S.I. CONVERSION FACTORS

In NBS Document LC 1056, revised August 1975, guidelines were established

to reaffirm and strengthen the commitment of NBS to the greatest practicable

use of the International System of Units (S.I.) in all of its publications

and also in all of its dealings with the science and engineering communities

and with the public. In this report the measurements are those of the

U.S. customary units as they appear in the referenced standards, in order

that the readers may give full attention to the organization and compilation

of the criteria.

The following conversion factors are appropriate for the units of measure

that appear in this report:

Energy

1 British thermal unit (Btu)

1 kilowatt-hour (kWh)

= 1055.056 joule (J) = 3600000.0 joule (J)

Temperature

1 degree Fahrenheit (°F) = (1.8) ^ kelvin (K) or (°K)

Temperature Fahrenheit (°F) = (459.67 + temp. °F)/1.8 (°K)

Time

1 hour (h) = 60 minutes (min) = 3600 seconds (s)

Volume

1 U.S. liquid gallon (gal) = 0.003785412 meter^ (m^)

= 3.785412 liters (L)

iv
TABLE OF CONTENTS

Page

LIST OF TABLES vi

LIST OF FIGURES vii

1. INTRODUCTION 1

2. INSTRUMENTATION USED FOR MONITORING USAGE OF DISHWASHERS,

CLOTHES WASHERS, AND CLOTHES DRYERS 3

3. ENERGY CONSUMPTION AND USAGE CHARACTERISTICS OF DISHWASHERS 4

4. ENERGY CONSUMPTION AND USAGE CHARACTERISTICS OF CLOTHES WASHERS H

5. ENERGY CONSUMPTION AND USAGE CHARACTERISTICS OF CLOTHES DRYERS 17

6. DISCUSSION OF RESULTS 23

7. CONCLUSIONS 26

REFERENCES 27

I V
LIST OF TABLES

Page

Table 1. Occupant and townhouse characteristics. 2

Table 2. Dishwasher characteristics. 5

Table 3. Average daily usage characteristics of dishwashers. 6

Table 4. Average per use characteristics of dishwashers. 10

Table 5. Clothes washer characteristics. 12

Table 6. Average dally usage characteristics of clothes washers. 13

Table 7 . Average per use characteristics of clothes washers . 16

Table 8. Clothes dryer characteristics. 18

Table 9. Average daily usage and per cycle use characteristics of

clothes dryers . 19

Table 10. Average daily energy consumption of dishwashers, clothes

washers and clothes dryers. 24

Table 11. Comparison of results from the Twin Rivers test site with

other sources [8] . 25

vi
LIST OF FIGURES

Page

Figure 1. Dishwasher daily energy consumption, townhouse #8. 7

Figure 2. Dishwasher daily water consumption, townhouse #8. 8

Figure 3. Dishwasher daily maximum water temperature, townhouse #8. 8

Figure 4. Clothes washer dally energy consumption, townhouse #8. 14

Figure 5. Clothes washer daily hot water consumption, townhouse //8. 14

Figure 6. Clothes washer daily cold water consumption, townhouse //8. 14

Figure 7. Clothes washer daily maximum water temperature, townhouse #8. 15

Figure 8. Clothes washer daily usage, townhouse #8. 15

Figure 9. Clothes washer daily usage duration, townhouse #8. 15

Figure 10. Gas clothes dryer dally energy consumption, townhouse #8. 20

Figure 11. Electric clothes dryer daily energy consumption, townhouse #9. 21

Figure 12. Clothes dryer dally usage, townhouse #8. 22

Figure 13. Clothes dryer daily usage duration, townhouse #8. 22

Figure 14. Clothes dryer daily maximum exhaust temperature, townhouse #8. 22

\ vii
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1 . INTRODUCTION

The usage patterns of dishwashers, clothes washers, and clothes dryers from a field experiment for single-family dwellings are presented. This was part

of the Appliance Labeling Program* to Investigate the usage and energy con- sumption of these household appliances. The test site was ten selected townhouses located in Twin Rivers, New Jersey, occupied by typical families of

two adults and one to three children aged from 1 to 15 years. A summary of

occupants in each townhouse is given in table 1 . The chosen community in

Twin Rivers, New Jersey had been studied extensively by researchers in

Princeton University [1, 2]. The ten townhouses were selected by their previous energy usage data as a reasonable but small sample to reflect the total

energy usage of a townhouse community. The appliances were those installed

in the townhouses either supplied by the builder or replaced by the occupants.

No attempt was made to select any particular manufacturer’s model of any of

the three appliances. The measurement period was from spring of 1976 to summer of 1977.

Since none of these appliances would be operated continuously by occupants,

data were collected only during the occurrences of operations. The data

acquisition system recorded a scan of .all channels whenever the status of an event changed for any of these appliances in the townhouse. In this way,

both the frequency and the duration of usage could be recorded.

Studies of these appliances were aimed at obtaining data on their energy

consumption, water consumption, and frequency of usage. Measurements also

included temperatures of water supply to dishwashers and clothes washers, and

the exhaust temperature of clothes dryers. The energy needed for heating hot

water for dishwashers and clothes washers was calculated using the water

heater's characteristics presented in [3] and the measured hot water consumption of the appliance. It was found that the energy requirement for heating

hot water is approximately 10 times that for operating the appliances. Since

the water heater is an independent appliance, energy usage for heating hot

water depends on the efficiency of the water heater. Usage patterns of the

dishwasher and clothes washer have the most effect on energy conservation

because these appliances account for the majority of residential hot water

consumption. As for clothes dryers, the gas dryers with pilot light burners

showed that the energy loss due to continuous burning of the pilot was approximately 6 to 7 cubic feet of gas per day. The pilot lights constituted about

50 percent of the average dally energy consumption of the gas dryers. Dryers

with electric ignition burners had a lower average energy consumption as well

as operating energy consumption rate. The average consumption rate was calculated as the energy consumed per hour when the dryer was being operated.

Each of these major appliances—dishwashers, clothes washers, and clothes

dryers—will be discussed separately in the following sections.

This project was initially sponsored by the Energy Appliance Labeling

Program of the Center for Consumer Products Technology, National

Bureau of Standards, through an interagency agreement with the Federal

Energy Administration (now the Department of Energy)

.

\

1
Table 1. Occupant and Townhouse Characteristics

Townhouse

Number

Electric

or GasNumber of

Adults

Number of

Children

Children'

Ages

Number of

Bedrooms

1 E 2 2 6,8 3

2 E 2 1 6 3

3 G 2 1 3 2

4 G 2 3 6,7,9 3

5 E 2 2 10,13 3

6 E 2 2 10,13 4

7 G 2 2 2,4 3

8 G 2 2 1.3 3

9 E 2 1 15 3

10 E 2 2 2,6 2 converted

to 3

V

2
2. INSTRUMENTATION USED FOR MONITORING USAGE OF DISHWASHERS, CLOTHES

WASHERS, AND CLOTHES DRYERS

Instrumentation was Installed in each townhouse so that the energy and water

usage of the clothes washers, clothes dryers and dishwasher were measured

using electric or gas meters, and water meters, depending on the type of

appliances. Standard utility meters were modified to produce a pulse train

proportional to the quantity of energy or water used. For electric meters,

two holes were drilled in the Faraday disk and an optical isolator was installed such that a photo detector was actuated for each half revolution

of the disk (corresponding to 0.018 Wh). For gas meters, a square was attached to the 1/2 ft^ dial such that the corners of the square contacted a microswitch for each 1/4 revolution of the dial (corresponding to 1/8 ft^

of gas consumed). For water meters, a miniature magnetic reed switch was installed between the magnetic coupling of the metering mechanism and the

meter indicator. The arrangement produced a pulse for each 1/350 gallon of

water used. Then pulses were divided electrically by 32 to produce a pulse

for each 0.09 gallon of water. The pulse trains of each of these meters were summed by counters and the counters were read every five minutes by the data

acquisition system. Water meters were installed on hot and cold water

supplies of the clothes washer on the hot water supply to the dishwasher, and

on the cold water inlet to the water heater. Electric meters were installed

on the electrical lines to the dishwashers, clothes washers, and electric

clothes dryers. A gas meter was installed on the gas supply line to the gas

dryers. Thermocouples were also Installed on the hot water supply lines to

the clothes washers and dishwashers, and on the inlet and outlet water lines

of the water heaters. These thermocouples were attached to the surface of

the pipes and wrapped with insulation. Relays were installed on the clothes

washers and the clothes dryers. These relay contacts would be opened and

closed as these appliances were used. The closures were sensed by the

electronic control package of the data acquisition system which would scan

all channels when the appliance was turned on or off. This recorded the

number of times and duration the appliances were in use. The data gathered

by the data acquisition system were recorded on magnetic tapes which were processed on minicomputers at the Center for Building Technology to produce

the quantities reported herein.

>

3
3. ENERGY CONSUMPTION AND USAGE CHARACTERISTICS OF DISHWASHERS

The physical characteristics of dishwashers in each townhouse are given in

table 2. Measurements of operating characteristics on each dishwasher

included electrical energy consumption, water consumption, and maximum inlet

water temperature. Energy required by dishwashers is the sum of the electrical energy used to operate the unit and the energy used to heat the hot

water consumed in dishwashing. The energy for heating the hot water could

be calculated from the hot water consumption and the efficiency of performance

of the water heater in each townhouse [3].

The total energy consumption is

E-j = EH-y]^W (1)

where Eq- is the total energy consumption,

E is the electrical energy to operate the dishwashers in kWh,

W is the hot water consumption in gallons,

and is the average amount of energy per gallon of supplied hot water

from water heaters in kWh/gal for electric homes and in ft^/gal for

gas homes [3]

.

Table 3 gives the values of yi obtained from the hot

water heater characteristics of each home.

The energy unit of E-j- would be kWh for electric homes. However, for those

homes with gas water heaters, E and yi of equation (1) are not in the same energy units since they came from two different energy sources. For the

purpose of comparison, gas consumption was converted to Btu, so E-p is also

in Btu.

Average daily usage of dishwashers in each townhouse, together with the

corresponding water heater's characteristics is given in table 3. The hot

water usage per day of these dishwashers was between four to 10 gallons, with

an average of 6.5 gal/day. The percentage of hot water used for the dishwashing was between 5 percent and 25 percent with an average of 11 percent of total

hot water consumption. The electrical energy required to operate the dishwashers, E, was measured to be 0.1 to 0.5 kWh/ day, with an average of 0.27

kWh/ day, which is equivalent to about 17 percent of the total energy required to

wash the dishes per day. This result confirmed the estimated figures of the

dishwashers' energy usage [4] .

The daily profiles of electrical energy usage, hot water consumption, and

maximum water temperature of the dishwasher in townhouse #8 are shown in

figures 1 to 3. These profiles Illustrate the usage pattern of this particular dishwasher. Since the dishwashers were not utilized every day it would

be more appropriate to investigate the per usage characteristics among them.

Townhouse #8 is a typical unit to represent the general usage of these

appliances

.

\

4
2. INSTRUMENTATION USED FOR MONITORING USAGE OF DISHWASHERS, CLOTHES

WASHERS, AND CLOTHES DRYERS

Instrumentation was Installed in each townhouse so that the energy and water

usage of the clothes washers, clothes dryers and dishwasher were measured

using electric or gas meters, and water meters, depending on the type of

appliances. Standard utility meters were modified to produce a pulse train

proportional to the quantity of energy or water used. For electric meters,

two holes were drilled in the Faraday disk and an optical isolator was installed such that a photo detector was actuated for each half revolution

of the disk (corresponding to 0.018 Wh). For gas meters, a square was attached to the 1/2 ft^ dial such that the corners of the square contacted a microswitch for each 1/4 revolution of the dial (corresponding to 1/8 ft^

of gas consumed). For water meters, a miniature magnetic reed switch was installed between the magnetic coupling of the metering mechanism and the

meter indicator. The arrangement produced a pulse for each 1/350 gallon of

water used. Then pulses were divided electrically by 32 to produce a pulse

for each 0.09 gallon of water. The pulse trains of each of these meters were

summed by counters and the counters were read every five minutes by the data

acquisition system. Water meters were installed on hot and cold water

supplies of the clothes washer on the hot water supply to the dishwasher, and

on the cold water inlet to the water heater. Electric meters were installed

on the electrical lines to the dishwashers, clothes washers, and electric

clothes dryers. A gas meter was Installed on the gas supply line to the gas

dryers. Thermocouples were also Installed on the hot water supply lines to

the clothes washers and dishwashers, and on the inlet and outlet water lines

of the water heaters. These thermocouples were attached to the surface of

the pipes and wrapped with insulation. Relays were installed on the clothes

washers and the clothes dryers. These relay contacts would be opened and

closed as these appliances were used. The closures were sensed by the

electronic control package of the data acquisition system which would scan

all channels when the appliance was turned on or off. This recorded the

number of times and duration the appliances were in use. The data gathered

by the data acquisition system were recorded on magnetic tapes which were processed on minicomputers at the Center for Building Technology to produce

the quantities reported herein.

\

3
3. ENERGY CONSUMPTION AND USAGE CHARACTERISTICS OF DISHWASHERS

The physical characteristics of dishwashers in each townhouse are given in

table 2. Measurements of operating characteristics on each dishwasher

included electrical energy consumption, water consumption, and maximum inlet

water temperature. Energy required by dishwashers is the sum of the electrical energy used to operate the unit and the energy used to heat the hot

water consumed in dishwashing. The energy for heating the hot water could

be calculated from the hot water consumption and the efficiency of performance

of the water heater in each townhouse [3].

The total energy consumption is

E-r = E + Yl W (1)

where E-p is the total energy consumption,

E is the electrical energy to operate the dishwashers in kWh,

W is the hot water consumption in gallons,

and is the average amount of energy per gallon of supplied hot water

from water heaters in kWh/gal for electric homes and in ft^/gal for

gas homes [3]

.

Table 3 gives the values of yj obtained from the hot

water heater characteristics of each home.

The energy unit of E-p would be kWh for electric homes. However, for those

homes with gas water heaters, E and yp of equation (1) are not in the same energy units since they came from two different energy sources. For the

purpose of comparison, gas consumption was converted to Btu, so Ep- is also

in Btu.

Average daily usage of dishwashers in each townhouse, together with the

corresponding water heater's characteristics is given in table 3. The hot

water usage per day of these dishwashers was between four to 10 gallons, with

an average of 6.5 gal/day. The percentage of hot water used for the dishwashing was between 5 percent and 25 percent with an average of 11 percent of total

hot water consumption. The electrical energy required to operate the dishwashers, E, was measured to be 0.1 to 0.5 kWh/ day, with an average of 0.27

kWh/ day, which is equivalent to about 17 percent of the total energy required to

wash the dishes per day. This result confiraed the estimated figures of the

dishwashers' energy usage [4]

.

The daily profiles of electrical energy usage, hot water consumption, and

maximum water temperature of the dishwasher in townhouse #8 are shown in

figures 1 to 3. These profiles illustrate the usage pattern of this particular dishwasher. Since the dishwashers were not utilized every day it would

be more appropriate to investigate the per usage characteristics among them.

Townhouse #8 is a typical unit to represent the general usage of these

appliances

.

\

4
Table 2. Dishwasher Characteristics

Townhouse

Number Model* Short Cycle

1 A no

2 A no

3 B no

4 B no

5 A no

6 A no

7 C no

8 C no

9 D no

10 E no

* All dishwasher models were from the same manufacturer,

supplied by the developer or purchased by the occupants.

Code letters A, B, C etc. indicate different models

5
Table

3.

Average

Daily

Usage

Characteristics

of

Dishwashers

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6
ENERGY

CONSUMED

-

KWH

PER

DRY

Figure 1. Dishwasher daily energy consumption, townhouse //8

.

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DRY
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8
Table 4 reports the average per usage measurements of dishwashers, obtained

from the daily data. It is interesting to find out that the occupants in

these townhouses used dishwashers on an average of once every two days. The

average electrical energy to wash one load of dishes, Ey, is 0.55 kWh, and

the average water consumption per each load of dishes, W, is 13.8 gallons.

The variations in water usage per load, from 10 to 18 gallons, were due to

the adjustments of water valves. For example, dishwasher models of townhouses

#1 and #2 were identical, but their per-load hot water consumption was quite

different; the values were 18.51 gal/use and 11.24 gal/use, respectively.

The valve adjustments were manually set at different settings when the

dishwashers was first installed.

The data acquisition system was designed to monitor major appliances such

that two adjacent townhouses (e.g. #1 and #2) would be considered as a pair

for data recording. Most of the appliances in each pair of townhouses were also selected with the same models for the purpose of comparison.

Table 4 shows that the values of Ey seem to follow the pattern of dishwasher

models in the townhouses given in table 2, meaning that energy used per cycle

is a function of appliance design. Except for townhouses #9 and #10, which

had unmatched dishwasher models, table 4 shows that the difference in the

average electrical energy consumption per usage is less than 10 percent. The

value of for the dishwasher in townhouse #9 was close to that in townhouses

#5 and #6. This might be due to the fact that these three townhouses had

the same dishwasher models.

As pointed out earlier, the electrical energy used to operate the dishwasher,

E, is about 17 percent of the total energy required to wash the dishes.

Therefore, the estimated total energy needed, E^, to operate the dishwasher

for one cycle could be obtained from the overall average electrical energy

per load, E^, as follows:

( 2 )

Because hot water consumption ranged from 10 to 18 gal/use (see table 4) this

is a rough approximation.

From table 4, E^ was given as 0.55 kWh; then

E^ = 3.3 kWh or 11263 Btu or 11.3 ft^ of gas.

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4. ENERGY CONSUMPTION AND USAGE CHARACTERISTICS OF CLOTHES WASHERS

Table 5 gives the physical characteristics of clothes washers in each

townhouse. In addition to measurements similar to those taken on dishwashers

(electrical energy consumption, water consumption, maximum water temperature,

and number of usages), the total time of use was also measured. The water

consumption included hot water as well as cold water measurements.

By applying the same method as for the dishwasher to calculate the energy

for heating water, the total energy requirement for operating the clothes

washers could be obtained from equation (1). The energy unit of E'j is in

kWh for electric houses and in Btu for gas homes.

The average daily usage of clothes washers in each townhouse, together with

their water heater characteristic, is given in table 6. Since all clothes

washers had water level selections of low, medium, or high (L/M/H), and

cycle selections of normal or permanent press (N/P), their daily electrical

energy usages and water consumption, both hot and cold, would have a wider

variation range than the dishwashers. This was mainly due to the different

washing habits and soil conditions of clothes of the occupants.

The average electrical energy consumption of these clothes washers was found

to be approximately 0.13 kWh/day, which is about 10 percent of the total energy

usage for operating these appliances per day. This is also close to the

estimated figures in [4]. As for the hot water consumption, the average

usage was 7.5 gal/day, which is equivalent to 12 percent of the daily water

consumption of the water heaters. The cold water usage, except for the

clothes washers in townhouse #10, was about three times that of the hot

water usage, and the total water consumption was about 27 gal/day. As shown

in table 5, the clothes washer in townhouse #10 was a completely different

model from the rest, with more cycle selections. Data for this machine

indicates a higher hot water consumption and a lower cold water consumption

than other clothes washers. The hot water usage was even higher than the

cold water usage in general. That might be due to user selection of water

temperature. The average data (excluding townhouse #10) was also included

in table 6 as a comparison. Figures 4 to 9 display the daily profiles of

electrical energy consumption, hot and cold water consumption, maximum water

temperature, number of loads, and total time of usage of clothes washer in

townhouse #8 to demonstrate the variation of these parameters. Table 7 presented the average results of clothes washers for all townhouses. It was found that the occupants washed a load of clothes twice every three days,

for an average of 0.70 usage/day. The average duration of usage was about

20 minutes per day and slightly under 30 minutes per wash. These findings

were very close to the measurements reported by Purdue University [5]. As

far as the individual per usage data were concerned, electrical energy per

usage for all clothes washers was fairly close, especially for the same

models. The water consumption, both hot and cold, mostly depended on selected

water level. The duration per use was mainly a manual cycle selection

from occupants' individual habits and soil condition. Generally speaking.

11
to run the clothes washer once, the average electrical energy consumption

was about 0.19 kWli and the water consumption was about 40 gallons, in which

25 percent was hot water. The estimated total energy needed to wash each

load of clothes including heating hot water could be obtained as:

Erp = 1.9 kWh or 6484 Btu or 6.5 ft^ of gas.

Table 5. Clothes Washer Characteristics

Townhouse Level Cycle

Number Model* Selection Selection

1 A L/M/H N/P

2 A L/M/H N/P

3 B L/M/H N/P

4 B L/M/H N/P

5 A L/M/H N/P

6 A L/M/H N/P

7 C L/M/H N/P

8 C L/M/H N/P

9 C L/M/H N/P

10 D Cont. L-H 8-cycle auto.

Legend: L = Low

M = Medium

H = High

N = Normal

P = Permanent press

* All clothes washers except that in townhouse #10 were from the same manufacturer, supplied by the developer or purchased by the occupants.

They are all top-load models with water volume of approximately

40 gallons/load.

Code letters A, B, C etc. indicate different models.

12
Q; 0> O CD X DO 4J M-i (B ^ 4j :* o< f £ . » o o

4J O CB >>

CO 4J Q.

bJ 0) CJ C

a 0) ti2 C U ^

u o> u

O bJ CO U

4J fO O. "O

—. o •u a.

J-.4J 3 o

t-

:s O C9 3 0) cj IS CD .a

X o -u3

bJ U 0) 3

13

Values

O.n

6.88

20.32

27.20

115:

lU
HOT

WRTER

CONSUMED

-

GRLLONS

PER

DRY

Figure 4

DRY

Clothes washer daily energy consumption, townhouse #8.

9® - MEQN =5.81

110 130 150 170 DRY Figure 5.

Q

- o

>-

LU

Q.

- o

9 I CD

210

Clothes washer daily hot water Figure 6.

consumption, townhouse //8.

14

Clothes washer daily

cold water consumption

townhouse #8.

LITERS

PER

DRY
NUMBER

OF

WRSHER

USRGES

Figure 7. Clothes washer daily maximum water temperature, townhouse #8.

DRY DRY Figure 8. Clothes washer daily usage,

townhouse #8.

Figure 9. Clothes washer daily usage

duration, townhouse #8.

15
of

Clothes

Washers

C

dO o

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txj B z) U 3

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o

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3 2

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CO =?:2

CJ 3 -D

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1—

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CN »-H cn cn «3-

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CN p^ m

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CQ N—/ >» S_«' s»/

00 -3* sO O cn P*^ cn 00 3 Os

s: 1—CM rH CN CN M rH CN rH CN I-H s 3

L o O o o o o o o o O O

u m a^ m sO sO u so in o cn

<v m CN o r-^ p^ Oi <r CN os sO sO

CO r>. 00 sO Os CO in (0 Os CN p^ c vO

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o a^ o^ m CN OO O' o o O rH O CO

. 0) 1—

(

CN so vO cn rH o so CO cn 00 sC

CO cn SO rv in CN rH CO -3- rH CO cn rH

L

)

rH rH rH rH rH rH rH rH

m CN SO rH in cn CN P^ o

sO 00 sO m O sO p>.

1 4

)L c C o O O O o o rH o ^ 1

05

0}

CO 3 05 o rH 0> e Cd e o CO > c X a; X E 0^ O 00 rH u rH <N m sO Os o X cn -3- r». 00 CO -H a rH u < 0) CO (U 1—

(

Cd > iM

u: o < 0

o

O

16

without

TH//10
5. ENERGY CONSUMPTION AND USAGE CHARACTERISTICS OF CLOTHES DRYERS

The function of clothes dryers is to evaporate the moisture in damp clothes.

Energy is required to supply heat to the drum and to rotate the drum witli a load of clothes. Energy consumption for operating this appliance is the

main concern for studies on energy conservation of both electric and gas

dryers. The physical characteristics of clothes dryers in each townhouse

are given in table 8. With regard to the manufacturer's design of the

clothes dryer, besides the heat input, there are other factors which affect

energy usage of dryers, such as rotating speed, blowing capacity, and air

flow patterns Inside the dryer. For our purpose, it is sufficient to record

energy consumption, number of uses, time of use, and exhausted air temperature. From these measurements the energy consumption per usage and per hour

of operation are determined.

Table 9 presents clothes dryer data on a daily basis as well as on a per-use

basis. The electric energy consumption of electric dryers, in kilowatt hours,

includes energy for heat input, rotation of drum, and blowing of air. For

gas dryers, the gas consumption in cubic feet considers only energy needed

to heat the air, without measurement of the required electric energy for drum

rotation and air blowing. For the purpose of comparison, conversions from

both kilowatt hour and cubic feet of gas to Btu were also included in table 9.

In addition, table 9 indicates that the occupants in these townhouses utilized

dryers on an average of twice every three days (0.77 usage/day) and a little

over 30 minutes per day. Furthermore, the average time of running a load was calculated to be about 42 minutes.

For electric clothes dryers, the average energy consumption was measured as

1.37 kWh/day and 2.07 kWh/load. Since the majority of clothes dryers had

timers to control the running time, the length of time for each load would

have a large variation, as would the per-usage consumption. As a standard

method for comparison, the energy consumption for operating individual

clothes dryers for one hour was obtained. The average value was found to be

2.83 kWh/hr, which is equivalent to 9659 Btu/hr. With gas dryers, the average energy consumption in operation was 97.3 cubic feet of gas per hour

(i.e., 9730 Btu/hr). Since the gas consumption was not including electrical

energy, gas dryers would require additional operating energy. From other

articles [6] it was estimated that approximately 10 percent should be added

for operating energy.

Figures 10 and 11 illustrate the energy consumption of clothes dryers in townhouses #8 and #9, respectively, to show the pattern of occupant usage. The

amount of constant usage in townhouse #8 was due to the pilot light of the

dryer burning continuously. The per-hour usage analysis for those dryers with

pilot lights (townhouses #7 and #8) was a little different, since the energy

burned by pilots was independent of appliance usage. Table 9 also indicated

that the pilot lights in townhouses #7 and #8 consumed more than 50 percent

of the total daily energy usage for gas dryers; the values were 7.04 and

5.80 cubic feet per day of gas, respectively. Even though the energy consumption of domestic clothes dryers is only a small portion of the total amount

of national energy usage, it is still worth considering other alternatives

17
to eliminate this waste. For the purpose of energy conservation, most

manufacturers have switched to electric ignition burners for gas dryers to

replace pilot lights. The changeover has taken place during the last 10 to

15 years [7]. Figures 12 to 14 represent the frequency of usage, duration

of usage, and maximum air temperature of clothes dryer in townhouse //8.

Table 8. Clothes Dryer Characteristics

Electric Dryers

Townhouse

Numbe r Model* Auto-Dry

1 A yes

2 B no

5 B no

6 B no

9 B no

10 B no

Gas Clothes Dryers

Townhouse

Number Model* Auto-Dry Ignition

3 C no Electronic

4 D no Electronic

7 E no Pilot

8 E no Pilot

* All clothes dryer models except that in townhouse #1 were from the same manufacturer supplied by the developer or purchased by the

occupants. They are all front load models.

Code letters A, B, C etc. indicate different models.

18
Table

9.

Average

Daily

Usage

and

Per

Cycle

Use

Characteristics

of

Clothes

Dryers

C

M-i 0) o o o -O' -O' o o o O j O E 00 00 p- 00 00 00 00 I 0) CN CM f-H CM CM pHt pH ' CO U ^ 3 1 CO 00 o^ NO 1 nO O o m m 11 CO CO fO 1^ ON ON m cn ON ON 1 O <TJ CM CM CM CM 1 0) 1 S 11

>> 11 CO

C T3 O

•H

p ji

OJ -^' o 1 to o. a CO o 00 ' ClU B 4J • • 1 iLi 0) 3 4J 44 r-- m 1 c CO o

tx3

C 1-H O *H o a

4-1o

CN CMm NO ON 3 o o O o c C <f 00 fH NO m AJ vO rH On nO cn o •ic CT> rv. CM ON nO OQ CO r— rH nO 1 •H 00 o ON On On nD ON o CM C?N

4-> c IH pH pH a o 3 B •r^ 4-» 3 AJ Vj az

CO CO 3

Qi c o

a: 0 <u ^ a CN s£> o cn CM CA CO nO ^4 o NO o u s£> 1-^ r— ON 00 4-) CO r- p4 NO r0) *c 4^

oc ui

a CsJ

m CM CM CM NO ON o CM ON

u o pH pH

Q) U-l c

U3

m r-. '0' -O' 3 c o o o 1 o^ o -O' NO -O' NO AJ m o c^ 3 CO o sO o o oa ON iH ON m ! c 4J vO r-. r-- On r- m in CM 00 o CQ pH pH I •H IJ 3) 60 D-1" 1 bZ U E

=>

<i) 3 j: oc -O'Om P-. cn

m c m -5- c “ Sn lA r>* CM nO o 4J ON ON in 1 bZ <= n jx! • • • • 9 44 • • • • 1 O Cl. i-H CM CM CM CM CO m CM 00 ' U pH pH 11

01

m

m 00 On -O'

u o CM nD pH CM 1 OJ OO U \0 o nO NO 03 cn On -cr o O' ' E M-J CO 03 m 00 CM r-- CO CM 00 pH On CM 1 •H O CO C/3 CsJ CM CM cn CM CM pH CM CM CM 1 E- 33 11

«4-l

Q 0 (U (0 r-4 r— ON

m o o o in cn cn cn

4J 00

U pM -O' CM o 03 cn cn cn r-- ON

0) CO 03 00 NO nO oc CO o X in ON c e CO u C/3 f—(

CM 1—4 CM r—i CM pH CM

•H 33 o; H a o >>

O

OJ co^ 00 vC CM 00

O in 1—i

P-- 00 00

00 v3 <f r-.

m 00 NO ON ON pH NO O'

a; CO • • • • • • • • Xi CO u O o O o o o c o pH d o B 33 0) 0 &. Z c o o c o CNJ o^ -O' nO NO o in NO pH 3 in v£> CM NO en r— 3 On On CM nO

4-» vO r>. iTi CM NO AJ

m MT in CM

00 D. T3 oa CA CN

m -O' I-- -O’ oa cn pH pH o u £3 P c CO a;

Ex] c a ON in NO pH o r«. iH CM CM CM r-- cn in ON CM NO o O 00 NO CM iH cn AJ • • • • • 44 CO -a' in CM o rH CM pH pH

0) 44 CO 44 0)

COO o u 03 o 03 3 •H 03 •H B 03 E o }-i CO OC to »-* o OO (0 0

J= 4j 03 COm <u CO a: CO 03 a: c ^ O e m NO ON o Ui 3 y 0) cn r-- 00 u 3 ? (L) o <u rH <L) e CO 0) to o X > Cfl o CC > CO CO H w < > Ex: X C < >

19

Hissing

Data
ENERGY

CONSUMED

CU

.

FT.

PER

DRY

16.0

24.0

32.0

40.0

48.0

56

.

90 110 130 150 170 190

DRY

Figure 10. Gas clothes dryer dally energy consumption, townhouse //8.

20

CU.

METERS

PER

DRY
!

MEPN =1.22

(

Figure 11. Electric clothes dryer daily energy consumption, townhouse

21

r

JOULES(»10'’)

PER

DRY
NUMBER

OF

DRYER

USAGE

mean =65.68 MEAN = 1972.77

townhouse #8.

Q

- LU'"

DPY Figure 13. Clothes dryer daily usage

duration, tov/nhouse .

LiJ®

I ®

a

CKc

LiJ,

ijJ

cc" X

X

LiJ®

X

CT®

90

MEAN =49.12

fL I n. I

1 10 130 150 170 DRY

190

® O

UJ ® UJ

O'

210

Figure 14. Clothes dryer daily maximum exhaust temperature, townhouse //8

22
6. DISCUSSION OF RESULTS

The measurement method used for determining energy consumption, water

consumption, and usage frequency of these major appliances was that of con- tinuous data recording in order to seek their average consumption as well

as usage patterns. Table 10 is summary of the total energy consumption and

hot water usage for all these appliances. The comparison between homes was somewhat difficult due to the fact that individual families had their own habits in operating these appliances. Furthermore, differences in usage

frequencies of household dishwashers, clothes washers, and clothes dryers

exist between values recorded from the test site and data obtained by other

sources for the Department of Energy (DoE)[^l. Considering the fact that the

measurement method used by other sources assigned by DoE was mainly field

data surveying rather than continuous field data recording, and their sample

sizes were much larger than those of the Twin Rivers site, discrepancies in

results of usage frequencies by these two methods were expected. However,

the per-load energy consumption and hot water consumption of these appliances

seemed to be in agreement, in spite of the difference in measurement methods.

Table 11 gives a comparison of average energy consumption, hot water consumption, and usage data of dishwashers, clothes washers, and clothes dryers

obtained from these two measurements.

23
00 Oc CM UO m cn 3 o « o^ r**. O o M CM ro CO O' ro o 03 rH rH CM rH CM

>» -o

00 c c U O 00 0> -H fo cvjC 4J ^ ^u: C.CN H e 2 a ^ a M (0 w • ro o^ vO oc \D

(V 4-» c ^ uo o O' in 1 0 o ^ 5 • •4C • H O W fO v£> m vO w

0)

j:: 4Jo cn CM in 00 o r*«. rH w 3 m o O' vO o oo c 4J o> * ON ro O' m Ui O tJ CO r«* m vO o 00

T3 (U *H c rH rH rH c C ^ (0

(0 row D. <N e “ 3 fO ro O' CM 'd- W (Q CO CM fC ro h-. CM

CM AJ

C

w S * • • • •

Nmx' o o CM rH ro in H O CM

U) o M

0) sO 0 4 CM so O'

.c nO rH in

m rH vO s4 CM cn CM 0 O' 4 (0 O' fs. O' CM 00 cn 00 3 r«. A CM 4 Px* sC

CO /-"s

m rH CM

A

A 00 4H rH O' rH sO O' r^ >N CM 3 A 00 rH ao <r m CM A rH rH rH OO C -w* 4J rH rH rH rH rH

CO 0 A 0) <u hH »0 c 4H c M CM W a. (0 0 e

rH 3 ^ O W CO CO rH vO 00 •4- vO -4 r>. M C w (C m CM <n cn \0

•*

O 0 3 • • •

/«*S

H 0 IM CM CM cn

m cn

rH 0 Nw<

COu >» CM

0> 00

C

w xi u 0

CO <i) •H

CO c 4H

C > w Cl cO

m cn

m CM 4 0 CM E vO rH A CM m 00 <r sO cn cn 4 4 CO 3 tC CM m m m m •4- m 3 •tH W U CO rH 5 • • • • • • • 0 0 0 0 0 0 Q 0> C w 0 0 0 0 0 0 0 rH 0

IM

W 0 «M o 0 co

•HM s Cl o U CM g o 0) w 3 rH 0» M

CO oo CO *3 c X «0 3 C r*% o M CO ^9 ^9 8^. d'? ^9 ^9 so 84 84 84 84 84 84 o ^ c M S'? 00 A •4“ O' \0 • B4 cn 0 CM rx. cn 4 3 0) 0 ^ CM rH rH CM CM CM CO CM cn CM rH CM

5o ^ u ac rH CM cn

OC CsJ

u CM

u rH 0) IM

0> 3 Qu 0 IM c 0 w

to •H

tH CM

CO

Cw

Q

U 0

0) •H H3

<u

M ^ C

00 (0 0. CO

m 0 nC O' CM CM O'

A CM cn

m rx. cO CNI3 E rH ao m cn 0 m 00 ao m 4* 0 O' C u 3 rH • •

0) 3 -U CO rH

M rH r- sC •4* CO CO rH

A 0 CM 4 o C w rH rH rH rH rH rH rH 00 rH rH rH rH r"4 rH 3: cS IM0 CO CO

Q CO <u

0)

r-< ^ rH i) 0) rH 0) ^ a ^ Ti CO

«J c > r

50 S > 2 X5 CO 0 u 0) X CO 3 •H Q) 0 E 1/ a> H 0 U 00 0^ 0 A /. X U (A (0 *H CO X ~ c CJ 01 rH CM in s£) O' 0 U W 0) m 4 rx. A L. 'J, u <

0>

g rH 0) E CO 0) 4) 0 *H 0 > 14.4 0 CO > ^ '1^ H tij X < 0 X c < 0 < 0 O

«H 00 00 m r**

iT) ^ \0

1-H iH

On

O'

oo00

r«

24
Table 11. Comparison of Results From the Twin Rivers Test

Site With Other Sources

Dishwashers Clothes Washers Clothes Dryers

j Twin

Rivers

Other

Sources

Twin

Rivers

Other

Sources

Twin

Rivers

Other 1 Sources i

Average energy

consumption - kwh/use 0.55 0.674* 0.19 0.22 2.07***

1 Average hot water

consumption - gal/use 13.81 15 9.40 12.49**

!

i Average annual load 197 416 255 416 281 416 ! J

* normal cycle only.

** WARM/COLD cycle assumption.

*** electric clothes dryers only.

25
7. CONCLUSION

As given by table 10, the electrical energy consumption for the hot water

consuming appliances, (dishwashers and clothes washers), Ej2» found to

be about 0.40 kWh/day; and the hot water consumption, W^2> approximately

14 gal/day or 23 percent of the total hot water heater’s daily consumption.

The total energy consumed by these two appliances turned out to be 11649

Btu/day, which is equivalent to 3.4 kWh/day or 11.65 ft^ of gas per day,

depending on the source of energy.

Gas clothes dryers with pilot lights have enormous standby losses, more than

50 percent of the total daily energy usage for the appliance. Furthermore,

the electric energy for drum rotation and air blowing were omitted from the

measurements of all gas dryers, so the actual total energy consumption of

gas dryers could not be determined. Therefore, only electric dryers were taken into account in investigating the actual combined energy usage of

these appliances.

Clothes washers and clothes dryers are normally considered to be a pair of

major appliances. Referring to tables 7 and 9, their frequencies of usage

for each townhouse were very close and the overall average usage per day was only 10 percent apart. As illustrated in figures 4, 8, 10 and 12, the

usage patterns of the washer and dryer in townhouse #8 shows that their

energy consumption is in agreement for days when they were in use. The

average energy consumption for the set of washer and dryer (electric), ^23* was found to be 3.5 kWh/ day and they were being used approximately twice

every three days or five loads each week.

For all three appliances, the average total energy consumption was calculated

to be 5.38 kWh/day. Again, only electric dryers were considered, as shown in

table 10. In addition, table 10 gives the energy units in Btu as well as kilowatt hours for both electric and gas homes, to reveal the actual energy

usage in each townhouse and to consolidate these appliances for conditions of

energy conservation. For example, gas dryers with pilot lights indicated a tremendous waste as compared to those with electric ignition burners.

Finally, the estimated combined energy consumption, from tables 3 and 7 and

the electric dryers’ average energy usage, was summed to be 7.27 kWh per

usage for all three appliances.

26
REFERENCES

1. Grot, R. A. and Socolow, R. H., "Energy Utilization in a Residential

Community," Energy Demand, Conservation and Institution Problems * ed. Michael Macrakis (Cambridge, Mass., MIT Press 1974).

2. Socolow, R. H., "The Twin Rivers Program on Energy Conservation in

Housing: Highlights and Conclusions," Energy and Buildings , Vol. 1,

No. 3, April, 1978.

3. Grot, R. A. and Galowin, L. S., "Preliminary Data on the Field

Performance of Storage-Type Residential Water Heaters," NBSIR 78-1496,

April, 1979. Available from NTIS, PB-295.431.

4. Fuchs, A. J., "Water Temperature Effects in Laundering and Automatic

Dishwashing," Proceedings of the Conference on Major Home Appliance

Technology for Energy Conservation, Purdue University, West Lafayette,

Indiana, pp. 180-185, February 27-March 1, 1978.

5. Tree, D. R., Hamilton, J. F. and Herrick, R. W., "Energy Measurements

of Major Home Appliances in Four Residential Homes," Proceedings of the

Conference on Major Home Appliance Technology for Energy Conservation,

Purdue University, West Lafayette, Indiana, pp. 214-228, February 27-

March 1, 1978.

6. Hollowell, G. T., "Clothes Dryer Energy Consumption," ERDA Conference

on Technical Opportunities for Energy Conservation in Appliances,

May 11, 1976.

7. Cox, J. D., and Kornguth, H., "Appliance Energy Conservation through

the Application of Electric Ignition Systems," Proceedings of the Conference on Major Home Appliance Technology for Energy Conservation,

Purdue University, West Lafayette, Indiana, pp. 225-264, February 27-

March 1, 1978.

8. Davies, A.D., Kelly, R., Lewis, A.C., Lovett, C.D. and Wang, T.J.,

"Household Appliance Usage Data," NBSIR 80-1994, February 1980.

27
NBS-114A (REV. 2*60

U.S. OEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR 2 REPORT NO.

NBSIR 80-2136

. Performing Organ. Report NoJ 3. Publication Date October 1980

4.

TITLE AND SUBTITLE

ENERGY CONSUMPTION AND USAGE CHARACTERISTICS FROM FIELD MEASUREMENTS OF

RESIDENTIAL DISHWASHERS, CLOTHES WASHERS, AND CLOTHES DRYERS

5. AUTHOR(S)

Yui-May L. Chang and Richard A. Grot

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7. Contract/Grant No. national bureau of STANDARDS

DEPARTMENT OF COMMERCE t. Type of Report & Period Covere ' WASHINGTON, D.C. 20234

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. Stole, ZIP)

10.

SUPPLEMENTARY NOTES

Q21 Document describes a computer program; SF-185, FIPS Software Summary, is attached.

II. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here)

The measured energy consumption and usage characteristics for household dishwashers,

clothes washers, and clothes dryers for ten townhouses at Twin Rivers, N.J., are presented. Whenever the dishwashers and/or clothes washers were in use, the energy

consumption, water consumption, frequency of usage, and water temperature were measured by a data acquisition system. The energy requirement for heating hot water

could be established from the water heater's characteristic in a previous related

report (NBSIR 78-1496). The electrical energy of electric clothes dryers and the

gas consumption of gas clothes dryers were measured, as well as their frequency

and duration of use, and exhaust temperature. Typical household usage patterns of

these major appliances are also Included.

It was found that, in general, the electrical energy required to operate dishwasherc

and clothes washers is about one tenth of the energy consumption for heating hot

water. Cold water usage is about three times the hot water usage for each load of

laundry. The energy loss from a pilot light burner of a gas dryer is about 50 percin

of the total gas consumption of that dryer. As far as habits are concerned, the

average family utilizes the dishwasher every other day and the laundry about five

loads a week.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

Clothes dryer usage characteristics; clothes washer usage characteristic; data

profiles; dishwasher usage characteristic; energy consumption; field measurements;

usage patterns; water consumption.

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