7

- i CH APTER 7

. ENERGY AND WATER USE DETERMINATION

TABLE OF CONTENTS

7.1 INTRODUCTION

................................ ................................ ................................ ............... 1

7.2 PER

- CYCLE ENERGY AND WAT ER CONSUMPTION BY EF FICIENCY

LEVEL

................................ ................................ ................................ ................................ . 1

7.3 AVERAGE ANNUAL ENERG Y AND WATER CONSUMPT ION BY

EFFICIENCY LEVEL

................................ ................................ ................................ ......... 6

7.4 VARIABILITY IN ANNUA L ENERGY AND WATER C ONSUMPTION:

WASHER CAPACITY AND USAGE TRENDS

................................ ............................... 8

LIST OF TABLES

Table 7.2.1 Top

- loading Standard

- Capacity Residential Clothes Washers: Per

- Cycle

Energy and Water Use by Efficiency Level

................................ ............................ 4

Table 7.2.2 Front

- loading Standard

- Capacity Residential Clothes Washers: Per

- Cycle

Energy and Water Use by Efficiency Level

................................ ............................ 5

Table 7.2.3 Top

- loading Compact Residential Clothes Washers: Per

- Cycle Energy and

Water Use by Efficiency Level

................................ ................................ ................ 5

Table 7.2.4 Front

- loading Com pact Residential Clothes Washers: Per

- Cycle Energy

and Water Use by Efficiency Level

................................ ................................ ......... 5

Table 7.3.1 Top

- loading Standard

- Capacity Residential Clothes Washers: Annual

Energy and Water Use by Efficiency Level

................................ ............................ 7

Table 7.3.2 Front

- loading Standard

- Capacity Residential Clothes Washers: Annual

Energy and Water Use by Efficiency Level

................................ ............................ 7

Tabl e 7.3.4 Top

- loading Compact Residential Clothes Washers: Annual Energy and

Water Use by Efficiency Level

................................ ................................ ................ 8

Table 7.3.3 Front

- lo ading Compact Residential Clothes Washers: Annual Energy and

Water Use by Efficiency Level

................................ ................................ ................ 8

LIST OF FIGURES

Figure 7.4.1 Trends in Washer Usage and Capacity

................................ ................................ .... 9 Figure 7.4.2 Annual Usage Distribution for Top

- Loading Clothes Washers

............................. 10 Figure 7.4.3 Annual Usage Distribution for Front

- Loading Clothes Washers

.......................... 10 Figure 7.4.4 Dryer usage for Households with Top

- loading Clothes Washers

.......................... 11 Figure 7.4.5 Dryer usage for Households with Front

- loading Clothes Washers

....................... 127

- 1 CHAPTER 7. ENERGY AND WATER USE DETERMINATION

7.1 INTRODUCTION

To perform the life

- cycle cost (LCC) and payback period (PBP) calculations described in Chapter 8, DOE had to determine the savings in oper ating costs that consumers would derive from higher efficiency standards for clothes washers. DOE used consumer energy and water use data, along with energy and water prices, to develop the most significant component of consumer operating costs in the LCC and PBP analyses * . This chapter describes how DOE establish ed the

annual energy and water consumption of residential clothes washers.

7.2 PER

- CYCLE ENERGY AND WAT ER CONSUMPTION BY EF FICIENCY

LEVEL

DOE establishes the annual energy and water consumption of clo thes washers by multiplying the per

- cycle energy and water use by the number of cycles per year. The per

- cycle energy consumption associated with a given clothes washer has three components: energy used for heating the water, operating the machine, and dry ing the clothes. DOE adopted test procedures for clothes washers in a final rule published on October 18, 2005. 1 That DOE test procedure provides the following equations to calculate total per

- cycle energy consumption of

clothes washers.

Where:

CW CYCLE = total (without off

- mode energy use) per

- cycle energy consumption of clothes washer,

HE T = per

- cycle energy consumption for heating water [kilowatt

- hours

(kWh)/cycle)],

e = efficiency of electric water heater (100%) or gas water heater (75%),

ME T = per

- cycle machine energy consumption for operating washer (kWh/cycle),

and

D E = per

- cycle energy consumption for removing moisture from test load [ i.e.

,

dryer energy consumption (kWh/cycle)].

The following equation from th e current DOE test procedure calculates the per

- cycle energy consumption for removing moisture:

* Maintenance and repair costs are the other contributors.7

- 2

Where:

LUF = load usage factor

, W = weight of test load [pounds (lb)/cycle],

RMC = moisture content that remains after washing (lb ),

DEF = nominal energy required for a clothes dryer to remove moisture from clothes (0.5kWh/lb), and

DUF = dryer usage factor, a percentage of washer loads dried in a clothes dryer (0.91)

.

For clothes washers with manual fill control systems, only the L UF
max and LUF min terms are used. For clothes washers with adaptive fill control systems, all three terms are included. The values of W and LUF can be found in the current test procedure.

When considering gas drying, DOE multiplies the dryer energy consum ption by a gas correction factor to account for the additional energy a gas dryer requires relative to an electric dryer. The following equation determines per

- cycle energy consumption for gas drying.

Where:

D G = per

- cycle ener gy consumption for gas dryer to remove moisture from test

load, i.e. , dryer energy consumption (kWh/ cycle), and

GCF = gas correction factor = 1.12. 2

DOE previously used a modified energy factor (MEF) and a water factor (WF) to establish the energy and water efficiencies of clothes washers. The following equations

determine the MEF and WF :

Where:

C = container capacity [cubic feet (cu ft)], and Q T = per

- cycle water consumption for cold wash/cold/rinse [ gallons (gal)/cycle].7

- 3

The previous test procedure was revised to include non

- active mode energy use. 3 This analysis takes those revisions into account by using the revised integrated energy and water

factors defined below.

IMEF = C / (CW cycle +cycli c off

- mode energy )

The cyclic off

- mode energy is expressed in units of kWh/cycle and obtained by dividing

the annual off

- mode energy use by the number of wash cycles per year.

The integrated water factor is defined below.

IWF = Qt / C

Where: Qt = Tot al weighted per

- cycle water consumption for all wash cycles C = Capacity

As discussed in the Engineering Chapter, DOE analyzed specific energy efficiency levels for top

- and front

- loading standard

- capacity and compact residential clothes washers. Table 7.2.1 and 7.2.2 show the efficiency levels for standard

- capacity residential clothes washers and their corresponding per

- cycle energy and water use. Since the capacity varies with efficiency level

there is a column including th at volume variable (“ Vol. ft 3 ”) . Both MEF and IMEF are also

listed. The IMEF can be used to calculate total kWh/cycle , which can be br oken down further into machine, dryer, and water heating energ y

. For example, in the table for top

- loading washers

the volume of 3.09 cubic feet divided by an IMEF of 0.84 results in a total kWh/cycle of 3.67

kWh

, which also equals the sum of machine, dryer and water heating ene rgy per cycle. Tables 7.2.3 and 7.2.4 show the efficiency levels and the corresponding per cycle energy and water use for the two compact product classes.

Per

- cycle energy use is disaggregated int o energy used for heating the water, operating the machine, and drying the clothes. DOE determined the per

- cycle clothes drying energy use by using RMC values contained in the cost/efficiency data from the engineering analysis . DOE obtained the per

- cycle m achine energy use from the cost/efficiency data set. After obtaining the

per

- cycle energy use for drying the clothes and operating the machine, DOE determined the per

cycle water

- heating energy use. First DOE determined the total per

- cycle energy use (the washer container volume divided by the IMEF) and then subtracted from it the per

- cycle clothes

- drying, standby

, and machine energy use. The water

- heating energy use assumes the use of an electric water heater. DOE determined the per

- cycle hot water use by dividing the per

- cycle water

heating energy use by an assumed temperature rise of 75 oF (21.1 oC) and a specific heat of 0.0024 kWh/gal

- oF (4.186 joule/gram

- oC). DOE determined the total water use by multiplying the IWF by the washer container volume.7

- 4

So me of the variables in the following four tables were calculated using average values. These average values are not used in the LCC analysis described in Chapter 8. The IMEF

includes off

- mode energy use and requires using an average value for washer usage (295 cycles/year). An average dryer usage factor of 0.91 is used to calculate dryer energy use and this also impacts the calculation of water heater energy use; therefore, average values for these two quantities are shown in the two tables. When carrying o ut the LCC analysis, washer usage is selected from households in RECS. This methodology is described in Chapter 8.

Table 7.2.1 Top

- loading Standard

- Capacity Residential Clothes Washers: Per

- Cycle

Energy and Water Use by Efficiency Level

Level Vol

(ft 3 ) Watts MEF * IME F * IWF (gal/cu ft) RMC

( %) Energy Use (kWh/cycle)

Machine Dryer Water

Heat + Hot

Water gal/cycle

Baseline 3. 09 0.00 1.26 0.84 9.92 51.9% 0.279 2.16 1.24 6.90

1 3. 38 0.00 1.40 0.98 9.92 53.6% 0.281 2.43 0.74 4.13

2 3. 38 0.00 1.72 1.29 8.44 48.8 % 0.228 1.69 0.69 3.85

3 3. 76 2.30 1.80 1.34 7.95 37.9% 0.082 1.41 1. 26 7. 02

4 3. 76 1.70 1.80 1.34 7.95 37.9% 0.082 1.41 1. 26 7. 02

5 3. 76 0.08 1.80 1.37 7.95 37.9% 0.082 1.41 0 125 4.92

6 3.86 0.08 2.00 1.57 6.47 36.6% 0.082 1.38 0.99 5.5 0

7 3.96 0.08 2.26 1.83 4.96 36.6% 0.077 1.41 0.6 7 3.7 4

8 4. 34 0.08 2.47 2.04 4.10 34.8% 0.082 1.39 0.66 3.6 7

* cubic feet/kWh/cycle + based on use of electric water heater7

- 5

Table 7.2.2 Front

- loading Standard

- Capacity Residential Clothes Washers: Per

- Cycle

Energy and Water Us e by Efficiency Level

Level Vol (ft 3 ) Watts MEF * IMEF * IWF (gal/cu ft) RMC

( %) Energy Use (kWh/cycle)

Machine Dryer Water

Heat § Hot

Water gal/cycle

Baseline 3.00 2.30 1.72 1.37 8.31 41.4% 0.113 1.31 0.6 9 3

. 86

1 3.00 1.70 1.72 1.39 8.31 41.4% 0 .113 1.31 0. 69 3

. 82

2 3.00 0.08 1.72 1.41 8.31 41.4% 0.113 1.31 0.70 3.8 8

3 3.00 0.08 1.80 1.49 7.80 41.4% 0.113 1.31 0. 60 3.3 1

4 3.30 0.08 2.00 1.66 6.26 41.6% 0.163 1.42 0.40 2.2 2

5 3.41 0.08 2.20 1.84 4.73 38.6% 0.154 1.34 0.36 1

. 99

6 3.60 0.08 2.4 0 2.02 4.42 38.7% 0.164 1.41 0.20 1.1 3

7 3.83 0.08 2.60 2.20 4.01 36.2% 0.167 1.37 0.2 1 1.1 4

8 3.90 0.08 2.89 2.46 3.39 35.9% 0.155 1.38 0.04 0.2 5

Table 7.2.3 Top

- loading Compact Residential Clothes Washers: Per

- Cycle Energy and

Water Use by Efficiency Level

Level Vol (ft 3 ) Watts MEF * IMEF * IWF (gal/cu ft) RMC

( %) Energy Use (kWh/cycle)

Machine Dryer Water

Heat § Hot

Water gal/cycle

Baseline 1

. 50 0. 0 0 .7 7 0

. 59 14.4 58 0. 3 0 1.3 5 0. 90 4

. 98

1 1

. 59 0. 0 1. 6 2 0

. 86 14

. 4 58 0.1 0 1.3 5 0. 40 2

. 24

2 1.59 2.3 1.8 1 1.15 12.0 45 0.10 0.87 0.34 1.90

Table 7.2.4 Front

- loading Compact Residential Clothes Washers: Per

- Cycle Energy and

Water Use by Efficiency Level

Level Vol (ft 3 ) Watts MEF * IMEF * IWF (gal/cu ft) RMC

( %) Energy Use (kWh/cycle)

Machine Dryer Water

Heat § Hot

Water gal/cycle

Baseline 1

. 5 2.30 1. 60 1. 0 3 8. 8 45 0.1 0 1.02 0. 27 1

. 49

1 1

. 5 0 .0 8 1.72 1. 1 3 8.3 45 0.1 0 1.02 0. 20 1

. 137

- 6

7.3 AVERAGE ANNUAL ENERG Y AND WATER CONSUMPT ION BY

EFFICIENCY LEVEL

To determine the average annual energy and water consumption for a clothes washer, DOE multiplies the per

- cycle energy and water consumption by the number of cycles per year. Because the predominant application of re sidential clothes washers is single

- family housing

units

, including condominiums and mobile units, DOE c onsidered only those applications in determining the number of clothes washer cycles per year. Other applications may include lodging establishments ( e.g. , some hotels and motels), but those are a minor part of the market compared to single

- family housing units. DOE therefore believes it is not necessary for the analysis to accurately characterize residential clothes washer usage for applications other than single

- family and multi

- family housing units. In the LCC analysis, rather than using national

average s, DOE determines clothes washer use by using a distinct value from RECS for each

household

.

DOE uses the following equation to calculate the annual energy consumption in each

RECS household that is attributable to residential clothes washers.

Where:

C W ANNUAL = total annual energy consumption by clothes washers,

C W CYCLE = total per

- cycle energy consumption by clothes washers (C/IMEF), and

N = individual household annual clothes washer use (loads per year).

DOE used th e following equation to calculate the annual water consumption of

residential clothes washers.

Where:

C W ANNUAL WATER = total annual water consumption by residential clothes washers, and

C W CYCLE WATER = total per

- cycle water consumption by residential clothes washers.

The average annual energy and water consumption shown in Tables 7.3.1 through 7.3.4 reflect an annual usage of 295 cycles per year. This is the average usage obtained from RECS 2005. The total annual energy con sumption reflects the use of an electric dryer and electric water heater. Total annual energy use equals Volume divided by IMEF multiplied by 295. This includes

the non

- active mode energy use. To convert electric water heating energy to gas or oil water

he ating energy use first convert kWh to Btu then divide by 0.75 to account for the efficiency of

the water heater.7

- 7

Table 7.3.1 Top

- loading Standard

- Capacity Residential Clothes Washers: Annual Energy and Water Use by Efficiency Level

Level IMEF * IWF

(gal/cu ft) Annual Energy Use Annual

Water Use

Total Machine Dryer Water

Heat

(kWh) (kWh) ( kWh) ( kWh ) (1000 gal.)

Baseline 0.84 9.92 1085 82 637 366 9.04

1 0.98 9.92 1019 83 717 219 9.89

2 1.29 8.44 770 67 499 204 8.41

3 1.34 7.95 831 24 416 372 8.82

4 1.34 7.95 826 24 416 367 8.82

5 1.37 7.95 808 24 416 368 8.82

6 1.57 6.47 725 24 407 294 7.36

7 1.83 4.96 639 23 416 200 5.79

8 2.04 4.10 629 24 410 195 5.25

Table 7.3.2 Front

- loading Standard

- Capacity Residential Clothes Washers: Annual Energy and Water Use by Efficiency Level

Level IMEF * IWF

(gal/cu ft) Annual Energy Use Annual

Water Use

Total Machine Dryer Water

Heat

(kWh) (kWh) ( kWh ) ( kWh ) (1000 gal.)

Baseline 1.37 8.31 644 33 386 205 7.36

1 1.39 8.31 637 33 386 203 7.36

2 1.41 8 .31 626 33 386 207 7.36

3 1.49 7.80 596 33 386 177 6.90

4 1.66 6.26 585 48 419 118 6.10

5 1.84 4.73 546 45 395 106 4.76

6 2.02 4.42 525 48 416 61 4.69

7 2.20 4.01 513 49 404 60 4.53

8 2.46 3.39 467 46 407 14 3.917

- 8

Table 7.3.4 Top

- loading Compact R esidential Clothes Washers: Annual Energy and Water Use by Efficiency Level

Level IMEF * IWF

(gal/cu ft) Annual Energy Use Annual

Water Use

Total Machine Dryer Water

Heat

(kWh) (kWh) ( kWh ) ( kWh ) (1000 gal.)

Baseline 0.59 14.4 750 90 398 262 6

. 37

1 0.86 14.4 545 30 398 117 6

. 76

2 1.15 12.0 408 30 257 102 5.63

Table 7.3.3 Front

- loading Compact Residential Clothes Washers: Annual Energy and Water Use by Efficiency Level

Level IMEF * IWF

(gal/cu ft) Annual Energy Use Annual

Water Use

Total Mach ine Dryer Water

Heat

(kWh) (kWh) ( kWh ) ( kWh ) (1000 gal.)

Baseline 1. 03 8. 8 430 30 301 80 3

. 89

1 1. 1 3 8.3 392 30 301 61 3 .6 3

7.4 VARIABILITY IN ANNUA L ENERGY AND WATER C ONSUMPTION:

WASHER CAPACITY AND USAGE TRENDS

Clothes washer usage measured in cycl es per year varies from one household to another and therefore, so do energy and water use. The magnitude of the annual usage has been decreasing while the average capacity of washers has been increasing. Figure 7.4.1 shows washer capacity using AHAM data plotted with usage data. Capacity has increased by about 14% from 1993 to 2005 while usage has decreased by about 17% 4 (RECS data) over the same time period. Assuming that any given household washes a fixed volume of clothes each year, this decrease in

usa ge indicates that on average, larger amounts of clothes are being washed in each load.

The test procedure provides measurement methods for washers with and without load sensors. For washers with load sensors the test procedure gives the greatest weightin g to a measurement with average loads (which means averaging maximum and minimum water fill results). This approach might result in calculated water and energy use that is unrealistically low if larger capacity washers tend to be filled with near maximum l oads rather than average loads.7

- 9

Figure 7.4.1 also shows washer usage decreasing over time. DOE has plotted results from analysis of RECS data and also market survey data. Both data sets show declining usage. The most recent average usage values from RECS 2005 and the market survey data show 295 and 309 cycles per year, respectively. Each study has an advantage and a disadvantage in how they

were conducted. The market survey study has actual point values for the weekly washes whereas the RECS study uses in tervals. On the other hand, the market survey study household size distribution does not match the Census values for household size as well as the RECS study. Household size affects washer usage. The market survey data set has fewer single

- person household s and more multiple

- person households. That can lead to a higher average usage value

as is the case for market survey data relative to RECS 2005. The RECS 2005 household size distribution is close to that for the latest Census Bureau sampling and the Ameri can Housing Survey (AHS).

Figure 7.4.1 Trends in Washer Usage and Capacity

DOE used RECS 2005 to determine the clothes washer usage in cycles per year for each household sampled in the LCC analysis. Figures 7.4.2 and 7.4.3 show the prob ability distribution of annual wash cycles for each product class. The average weighted usage is 295 cycles per year for top

- loading clothes washers and 320 cycles per year for front

- loading washers.



## Annual Wash Cycles / Average
Wash Tub Capacity

305

295 406

380

308 359

326

280 300 320 340 360 380 400 420

1981 1985 1989 1993 1997 2001 2005 Clothes Washer Cycles per Year

2.4 2.6 2.8 3 3.2 3.4 Tub Capacity (cu. ft)

RECS Market Survey Data Capacity7

- 10

Figure 7.4.2 Annual Usage Distribution for Top

- Loading Clothes W ashers

Figure 7.4.3 Annual Usage Distribution for Front

- Loading Clothes

Washers7

- 11

DOE also used RECS 2005 to determine the probability distribution of the dryer usage factors (DUF) for each household sampled. Figures 7.4.4 and 7.4.5 show the probability

distribut ion of DUFs for both product classes. The vast majority of households use their dryers after every wash load.

Figure 7.4.4 Dryer usage for Households with Top

- loading Clothes Washers7

- 12

Figure 7.4.5 Dryer usage for Households with Front

- loading Clothes

Washers

DOE used the REC S household samples with their associated annual energy usage and DUF to conduct the LCC and PBP analyses. See chapter 8 for more details on the LCC and PBP analysis.7

- 13

REFERENCES

1 U.S. Department of Energy

– Office of Energy Efficiency and Renewable Energy. Energy Conservation Programs for Consumer Products: Final Rule; technical amendment. Federal Register

. October 18, 2005. 70 FR 60407.

2 Biermayer, P.J. Preliminary Engineering Analysis for Clothes Washers . 1996. Lawrence Berkeley National Laboratory: Berkeley, CA. Report No. LBNL

- 47889, Appendix D.

October.

3 U.S. Office of the Federal Register. Title 10, Code of Federal Regulations, Pa rt 430

– Energy Conservation Program for Certain Commercial and Industrial Product, Subpart B, Appendix

JI

— Residential Clothes Washers . 2010. Washington, D.C.

4 Energy Information Administration. Residential Energy Consumption Survey 2005. http://www.eia.doe.gov/emeu/recs/contents.html