CHAPTER 7. ENERGY USE CHARACTERIZATION

TABLE OF CONTENTS

7.1 INTRODUCTION

........................................................................................................... 7-1 7.2 CONSUMER SAMPLES

................................................................................................ 7-2 7.2.1 Room Air Conditioners

.................................................................................................... 7-2 7.2.1.1 Residentia l Sample

......................................................................................... 7-2 7.2.1.2 Commercial Building Sample

........................................................................ 7-3 7.2.2 Clothes Dryer Household Sample

.................................................................................... 7-3 7.3 ROOM AIR CONDITIONERS

....................................................................................... 7-4 7.3.1 General Approach

......................................................................................................... ... 7-4 7.3.2 Operating Hours

.......................................................................................................... ..... 7-5 7.3.2.1 Residential

...................................................................................................... 7-5 7.3.2.2 Commercial

.................................................................................................... 7-8 7.3.3 Variability of Room Air Conditi oner Annual Energy Consumption

............................. 7-10 7.3.4 Average Annual Energy Consumption by Efficiency Level

......................................... 7-14 7.3.5 Estimating Room Air Conditi oner Energy Use by Month

............................................. 7-16 7.4 CLOTHES DRYERS

..................................................................................................... 7-16 7.4.1 Number of Cycles

......................................................................................................... . 7-16 7.4.2 Energy Use Calculation

................................................................................................. 7- 17 7.4.3 Variability of Annual Energy Consumption

.................................................................. 7-19 7.4.4 Average Annual Energy Consumption by Efficiency Level

......................................... 7-23

LIST OF TABLES

Table 7.2.1 Selection of RECS 2005 Record s for Residential Room Air Conditioner Samples

................................................................................................................ 7-2 Table 7.2.2 Selection of CBECS 2003 Records for Commercial Room Air Conditioner Samples

................................................................................................................ 7-3 Table 7.2.3 Selection of RECS 2005 R ecords for Clothes Dryer Sample

.............................. 7-4 Table 7.3.1 RECS Vintage Bins for Room Air Conditioner

................................................... 7-6 Table 7.3.2 Average Room Ai r Conditioner EER by Product Class and Year Sold

.............. 7-7 Table 7.3.3 Regression Equations

........................................................................................... 7-9 Table 7.3.4 Room Air Conditioner, Withou t Reverse Cycle and with Louvers, Less than 6,000 Btu/h: Average Annual Energy Use

................................................. 7-15 Table 7.3.5 Room Air Conditioner, Without Reverse Cycle and with Louvers, 8,000– 13,999 Btu/h: Average Annual Energy Use

...................................................... 7-15 Table 7.3.6 Room Air Conditioner, Without Reverse Cycle and with Louvers, 20,000 Btu/h or more: Average Annual Energy Use

..................................................... 7-15 Table 7.3.7 Room Air Conditioner, Wit hout Reverse Cycle and without Louvers, 8,000–13,999 Btu/h: Average Annual Energy Use

........................................... 7-16 Table 7.4.1 Number of Loads Washed per Week Based on RECS Sample

......................... 7-17 Table 7.4.2 RECS Sample Clothes Dryer Usage

.................................................................. 7-17 Table 7.4.3 RECS Sample Clot hes Dryers Utilization

......................................................... 7-17

7-iTable 7.4.4 Electric Standard and Gas Clothes Dryer: Average Annual Energy Consumption by Efficiency Level

..................................................................... 7-23 Table 7.4.5 Electric Compact Vented Dryer: Average Annual Energy Consumption by Efficiency Level

................................................................................................. 7-24 Table 7.4.6 Electric Compact Vent-less Dryer and Combination Washer/Dryer: Average Annual Energy Consumption by Efficiency Level

............................. 7-24

LIST OF FIGURES

Figure 7.3.1 Hours Above ANSI/ASHRAE St andard 55-2004 as a Function of Cooling Degree-Days

........................................................................................................ 7-9 Figure 7.3.2 Range of Annual Energy Us e for Residential Room Air Conditioners Without Reverse Cycle and with Louvers, Less than 6,000 Btu/h

.................... 7-11 Figure 7.3.3 Range of Annual Energy Us e for Residential Room Air Conditioners Without Reverse Cycle and with Louvers, 8,000–13,999 Btu/h

....................... 7-11 Figure 7.3.4 Range of Annual Energy Us e for Residential Room Air Conditioners Without Reverse Cycle and with Louvers, 20,000 Btu/h or more

..................... 7-12 Figure 7.3.5 Range of Annual Energy Us e for Residential Room Air Conditioners Without Reverse Cycle and without Louvers, 8,000–13,999 Btu/h

.................. 7-12 Figure 7.3.6 Range of Annual Energy Us e for Commercial Room Air Conditioners Without Reverse Cycle and with Louvers, Less than 6,000 Btu/h

.................... 7-13 Figure 7.3.7 Range of Annual Energy Us e for Commercial Room Air Conditioners Without Reverse Cycle and with Louvers, 8,000–13,999 Btu/h

....................... 7-13 Figure 7.3.8 Range of Annual Energy Us e for Commercial Room Air Conditioners Without Reverse Cycle and with Louvers, 20,000 Btu/h or more

..................... 7-14 Figure 7.3.9 Range of Annual Energy Us e for Commercial Room Air Conditioners Without Reverse Cycle and without Louvers, 8,000–13,999 Btu/h

.................. 7-14 Figure 7.4.1 Range of Annual Energy Use for Ve nted Electric Standard Clothes Dryers

.... 7-20 Figure 7.4.2 Range of Annual Energy Use for Vented Electric Compact 120V Clothes Dryers

................................................................................................................. 7-20 Figure 7.4.3 Range of Annual Energy Use for Vented Electric Compact 240V Clothes Dryers

................................................................................................................. 7-21 Figure 7.4.4 Range of Annual Gas Use for Vented Gas Clothes Dryers

............................... 7-21 Figure 7.4.5 Range of Annual Electricity Use for Vented Gas Clothes Dryers

..................... 7-22 Figure 7.4.6 Range of Annual Energy Use for Vent-less 240V Clothes Dryers

.................... 7-22 Figure 7.4.7 Range of Annual Energy Use fo r Vent-less Combination Washer/Dryers

........ 7-23

7-iiCHAPTER 7. ENERGY USE CHARACTERIZATION

7.1 INTRODUCTION
To carry out the life-cycle cost (LCC) and payback period (PBP) analyses described in chapter 8, DOE needs to determine the operating cost savings to consumers from more efficient products. The LCC and PBP analyses require data on annual energy use because, along with energy prices, DOE uses these data to establish the most significant component of consumer operating costs. Maintenance and repair costs are the other contributors to operating cost. This chapter describes how DOE determined the annual energy consumption of room air conditioners (RAC) and clothes dryers for use in the LCC and PBP analyses.

The engineering analysis described in chapter 5 reports energy use based on the DOE test procedure. This test provides standardized results that serve as the basis for comparing the performance of different applian ces used under the same conditions. Actual usage in the field varies depending on the conditions in which the appliances are operated. a

To establish a reasonable range of energy consumption in the field for room air conditioners and clothes dryers, DOE primaril y used data from the Energy Information Administration (EIA)’s 2005 Residential Energy Consumption Survey (RECS 2005). 1 RECS is a national sample survey of housing units that co llects statistical information on the consumption of and expenditures for energy in housing units al ong with data on energy-related characteristics of the housing units and occupants. RECS 2005 collected data on 4,381 housing units and was constructed by EIA to be a national representation of the household population in the United States.

Room air conditioners are predom inantly used in homes, but they are also used in some commercial buildings. To determine the energy use patterns of room air conditioners in commercial applications, DOE used EIA’s 2003 Commercial Building Energy Consumption Survey (CBECS) 2 to develop a representative sample of commercial buildings using room air conditioners. CBECS 2003 collected energy-related data for 5,215 buildings and was constructed by EIA to be a national representation of the commercial building stock in the United States.

The details of each building sample are described in the following section.

a DOE assembled estimates of the average annual energy use of room air conditioners from several studies and sources. Unfortunately, none of the studies is based on metered data. The studies rely on power measurements and assumptions regarding usage to derive the annual energy consumption values.

7-17.2 CONSUMER SAMPLES

7.2.1 Room Air Conditioners

7.2.1.1 Residential Sample
The subset of RECS 2005 records used for the room air conditioner sample met all of the following criteria:

• A room air conditioner served as the primary source of air conditioning.

• There were at most 3 room air conditioners reported.

• Room air conditioner energy cons umption was greater than zero.

Households were assigned to the sub-sa mples based on the amount of cooling area (square footage as given by RECS) per room air conditioner in the home. DOE reasoned that homes with relatively more cooling area per unit ha ve room air conditioners with higher cooling capacity. The correspondence between cooling area per unit and capacity was based on ENERGY STAR sizing guidelines for room air conditioners. b See appendix 7-A for more details. Table 7.2.1 shows the number of RECS records in each sub-sample. DOE used EIA’s weightings for each RECS 2005 household. The weightin gs indicate how commonly each household configuration occurs in the general population.

Table 7.2.1 Selection of RECS 2005 Records fo r Residential Room Air Conditioner Samples

Product Class Selection Criterion No. of Records No. of U.S. Households Represented (million) No. of U.S. RAC Units Represented (million) Total sample 1096 25.2 40.9
> 6000 Btu/h Cooling sq. ft. per unit < 250 374 13.3 23.7 8,000 to 13,999 Btu/h Cooling sq. ft. per unit between 250 and 650 635 24.6 49.8

2 20,000 Btu/h Cooling sq. ft. per unit 2 650 or energy use per unit > 10 MMBtu/yr 108 3.7 6.7

b http://www.energystar.gov/index.cfm?c=roomac.pr_properly_sized

7-27.2.1.2 Commercial Building Sample

The subset of CBECS 2003 records used for the commercial-sector room air conditioner sample met all of the following criteria:

• A room air conditioner served as a source of air conditioning. c

• Building is not vacant.

• A room air conditioner is used as the prim ary equipment to cool at least a portion of the building.

The sample was divided into sub-samples to match to the product classes analyzed. CBECS 2003 provides the total cooling square foot age and the fraction of cooling by the room air conditioner for each building record, but it does not provide the number of room air conditioners used by the building, so the total room air conditioner cooling square footage is used to determine the subsampl es. Table 7.2.2 shows the number of CBECS records in each subsample. DOE used EIA’s weightings for each CBECS 2003 building. The weightings indicate how commonly each building configuration occurs in the general population.

Table 7.2.2 Selection of CBECS 2003 Records for Commercial Room Air Conditioner Samples

Product Class Selection Criterion No. of Records No. of U.S. Buildings Represented (million) Total sample 440 0.4 >6,000 Btu/h Total RAC Cooling sq. ft. > 0 440 0.4

8,000 to 13,999 Btu /h Total RAC Cooling sq. ft. > 300 400 0.3

2 20,000 Btu /h Total RAC Cooling sq. ft. > 900 352 0.3

7.2.2 Clothes Dryer Household Sample

The subset of RECS 2005 records used for the clothes dryer sample met all of the following criteria:

• The household had a clothes dryer.

• Clothes dryer fuel was electri city, natural gas or LPG.

c PTAC systems could also be listed as room air conditioners, so DOE tried to select buildings with only room air conditioners. A building was selected as having a room air conditioner if it did not have a PTAC type heating system.

7-3• Clothes dryer use was greater than zero.

The sample was divided into three sub-samples to match to the product classes analyzed (Table 7.2.3). For compact electric dryers , DOE developed a sub- sample consisting of households with an electric dryer in multifamil y buildings, manufactured homes, and singlefamily homes with less than 1,000 square feet and no garage or basement, since DOE reasoned that these products are most likely to be found in these housing types.

Table 7.2.3 Selection of RECS 2005 Records for Clothes Dryer Sample

Product Class Selection Criterion No. of Records No. of U.S. Households Represented (million)
Electric Standard Dryer Has Dryer = Yes Fuel Type = Electricity Use of Dryer > 0 2655 67.0

Electric Compact Vented Dryer and

Vent-less Dryer Has Dryer = Yes Fuel Type = Electricity Use of Dryer > 0 Type of Housing = Mobile Home; Multifamily; or single family (<1000 sq. ft. and no garage or basement) 570 14.4

Gas Dryer Has Dryer = Yes Fuel Type = Natural Gas or LPG Use of Dryer > 0 756 20.3

7.3 ROOM AIR CONDITIONERS

7.3.1 General Approach
DOE calculated the annual energy consum ption of a room air conditioner using the following equation:

RAC ENERGY = (Capacity * OH)/EER

Where:

RAC ENERGY = Room air conditioner annual energy consumption (kWh/year), Capacity = rated capacity in Btu/h, OH = operating hours per year,

7-4EER = Energy Efficiency Ratio in Btu/h/W.

DOE began with the data reported by RE CS on the annual energy consumption (field energy consumption) for room ai r conditioning, referred to as FEC(all) RECS . The reported enduse quantities were not based on metering of individual appliances; rather, EIA used a regression technique to estimate how much of the total a nnual electricity consum ption for each household can be attributed to each end-use category. d The reported field energy consumption refers to the consumption of all of the room air conditioners in a home.

RECS also reports the number of room air conditioners in the home. Of all homes that use a room air conditioner, 35 percent have two ro om air conditioners and 14 percent have three or more room air conditioners. To estimate th e energy consumption of a single room air conditioner, referred to as FEC RECS, DOE divided FEC(all) RECS by the reported number of room air conditioners. Although in reality the utilization of each of the room air conditioners in a home may vary, DOE has no way to estimate such variation.

For commercial-sector room air conditi oners, CBECS does not report annual energy consumption for room air conditioning, so DOE estimated the energy consumption using variables specific to each building in the sample and data on cooling degree-days.

In conducting the analysis of energy use by products that would meet some future standard, DOE effectively substituted the room ai r conditioners in the sa mple residential and commercial buildings with a new product of iden tical product class (capacity) but with different energy efficiency. In order for the estimate of new room air conditioner energy consumption to reflect field conditions, DOE needed to estimat e the number of room air conditioner operating hours for each household or commerc ial building in the samples.

7.3.2 Operating Hours

7.3.2.1 Residential

DOE calculated the annual room air cond itioner operating hours for each residential sample unit using the following formula:

OH = (FEC RECS * EER RECS )/Capacity

Where:

OH = operating hours per year, FEC RECS = field energy consumpti on for a room air conditioner,

d The desire to use a large number of independent variab les without using a large number of interaction terms and the desire to adapt the regression pro cedures to account for heteroscedastic erro r terms led to the use of a nonlinear regression technique. For more information, see: ht tp://www.eia.doe.gov/pub/consumption/residential/append_c.pdf

7-5EER RECS = the estimated EER of the room air conditioner in the sample home, Capacity = the room air conditioner capacity in Btu/h.

The derivation of FEC RECS was discussed above. The capaci ty is given by the product class; DOE used the same representative capacities for each class as it did in the engineering analysis.

DOE estimated the EER of the room air conditioner in each sample household by matching the age of the room air conditioner given by RECS with the average EER for the specific product class in the year of its vintage. In RECS, the age of a room air conditioner is given in one of the five bins shown in Table 7.3.1. DOE assumed a uniform distribution within each vintage bin and assigned an age to the room air conditioner in each sample household.

Table 7.3.1 RECS Vintage Bins for Room Air Conditioner Bin Age of unit

1 Less than 2 years old 2 2 to 4 years old 3 5 to 9 years old 4 10 to 19 years old 5 20 years or older

Once the vintage year was determined, DOE assigned an EER to the unit equal to the average EER for the appropriate capacity for that year. To derive a time series of average EER by capacity, DOE began with data from AHAM on total shipment-weighted average EER for 1972–2007. 3 AHAM also provided average EER data by product class (capacity) for 2005– 2007. 3 To develop the EER values by product cla ss (capacity) for earlier years, DOE first assumed that all of the produc ts shipped in each product class had the minimum efficiency required by the standard in each particular year. DOE then estimated the shares of total shipments by product class in each year using data for 1990, 1993 and 2005–2007, and calculated a total shipment-weighted EER. DOE then calculated scalars for each year from the ratio of the actual total shipment-weighted EER to the calculated EER, and then applied the scalars to the minimum efficiency required fo r each product class in each year. Table 7.3.2 shows the AHAM data on total shipment-weighte d average EER and the average EER estimated for the representative product classes.

7-6Table 7.3.2 Average Room Air Conditioner EER by Product Class and Year Sold Year Shipment Weighted EER Derived Average EER*

< 6000 Btu/h 8000­ 13,999 Btu/hr (PC 3) 2 20,000 Btu/hr 8000­ 13,999 Btu/hr (PC 8) 2007 9.81 9.80 10.10 9.10 9.50 2006 10.02 9.80 10.40 9.20 9.50 2005 9.95 9.80 10.10 9.10 9.40 2004 9.71 9.70 9.86 8.83 9.15 2003 9.75 9.70 9.92 8.89 9.21 2002 9.75 9.70 9.92 8.88 9.21 2001 9.63 9.70 9.80 8.50 8.73 2000** 9.3 9.03 9.70 8.50 8.73

1999 9.07 8.56 9.63 8.50 8.73 1998 NA 8.56 9.63 8.50 8.73 1997 9.09 8.57 9.64 8.50 8.73 1996 9.08 8.55 9.62 8.50 8.73 1995 9.03 8.49 9.55 8.50 8.73 1994 8.97 8.42 9.47 8.50 8.73 1993 9.05 8.50 9.56 8.50 8.73 1992 8.88 8.31 9.35 8.50 8.73 1991 8.8 8.24 9.27 8.45 8.73 1990** 8.73 8.18 9.20 8.39 8.69

1989 8.48 7.95 8.95 8.15 8.45 1988 8.23 7.72 8.68 7.91 8.20 1987 8.06 7.56 8.51 7.75 8.03 1986 7.8 7.32 8.23 7.50 7.77 1985 7.7 7.22 8.13 7.40 7.67 1984 7.48 7.02 7.89 7.19 7.45 1983 7.29 6.84 7.69 7.01 7.27 1982 7.14 6.70 7.53 6.86 7.12 1981 7.06 6.62 7.45 6.79 7.04 1980 7.02 6.58 7.41 6.75 7.00 1978 6.72 6.44 7.25 6.60 6.85 1972 5.98 6.30 7.09 6.46 6.70

* Shaded area values were provided by AHAM 3
** Years in which standards became effective

The estimated mean number of operating hour s for the residential room air conditioner sample is 1,310 hr for the >6,000 Btu/h product class, 678 hr for 8,000 to 13,999 Btu/h product classes, and 394 hr for the 2 20,000 Btu/h product class. For comparison, the DOE test procedure uses 750 hours per year for all room air conditioners.

7-7To ensure that the estimated operating hours are representative of future conditions, DOE investigated whether the 2005 heating season covered by RECS reflects representative climate. DOE found that the number of cooling degree-day s (CDD) in 2005 was 12 percent higher than the 30-year average (1971–2000). DOE believes, however, that this year is a reasonable proxy for climate over the forecast period beginning in 2014. The AEO2008 includes a forecast of CDD that shows an increasing trend from 2010 to 2020. e The climate in 2005 is cl ose to the average in the AEO climate forecast.

7.3.2.2 Commercial
DOE calculated the annual operating hours for each sample commercia l-sector room air conditioner by establishing a re lationship between cooling degr ee-days and operating hours for a number of building type and bu ilding schedule combinations. DOE assumed that a room air conditioner is operated when the outdoor air conditions are above th e comfort zone described by ANSI/ASHRAE Standard 55-2004 Thermal Envir onmental Conditions for Human Occupancy. 4 To estimate how often this occurs, DOE used the following general equation:

OH55 = (a * CDD) + b

Where:

OH55 = Average annual hours when the outdoor air conditions are above the ASHRAE Standard 55 comfort zone, CDD = the number of annual cooling degree-days (65 F) for a given location;

a and b are linear fit parameters.

DOE used data on cooling degree-days fr om the National Solar Radiation Database (NSRDB). 5 The 1991–2005 NSRDB is an update of the 1961–1990 NSRDB. This updated NSRDB dataset is an hourly ground-based data set of solar and meteorological fields for 1,454 stations. A total of 858 sites have a complete 15-year period of record.

After removing the sites in Hawaii, Guam, and the Caribbean islands, regressions were done to predict the hours per year above Standard 55 from the number of cooling degree-days for each year. The data points and regression lines are shown in Figure 7.3.1 for all hours of the year. The data represent 842 sites for 15 y ears each in the continental United States.

e http://www.eia.doe.gov/oiaf /archive/aeo08/issues.html

7-8**hours/year above ASHRAE Std 55 CLDD vs #hours > ASHRAE Std55**  **all day, all year 1991-2005**

10000

y = 2.7592x + 127.99 9000 R 2 = 0.9224

8000

7000

6000 non-desert desert 5000 Linear (non-desert) Linear (desert) 4000

3000

y = 1.153x + 574.04 2000 R 2 = 0.8714

1000

0 0 500 1000 1500 2000 2500 3000 3500 **CLDD (base 65F)** Figure 7.3.1 Hours Above ANSI/ASHRAE Standard 55-2004 as a Function of Cooling Degree-Days

As can be seen in the graph above, the data patterns are different for desert locations, where humidity is not a present factor affectin g comfort. The regressi on equations developed from the data are shown in Table 7.3.3.

Table 7.3.3 Regression Equations R 2 Region Equation # sites Non-desert OH55 = 2.759 x CLDD + 127.99 0.9224 809 Desert OH55 = 1.153 x CLDD + 574.04 0.8714 33

For a given location, the number of an nual hours above the ASHRAE Standard 55 comfort zone varies by schedule, which refers to the time that a building is open. Thus, DOE performed the regression for a number of combin ations of building type and building schedule, yielding somewhat different equations for each combination. The building types included are: Assembly, Education, Food Service, Office, Retail, and Warehouse. For each building type, DOE estimated operating hours for the following building schedules: (1) open 24 hours a day and seven days a week (24/7); (2) open bus iness hours Monday through Friday; (3) open business hours Monday through Saturday; (4) op en business hours Monday through Friday and Sunday; (5) open business hours all week. Each of these schedules yields a variation of the above equations.

7-9To estimate the room air conditioner operating hours for each of the buildings in the CBECS room air conditioner sample, DOE identified the building type and the building schedule using information provided by CBECS, and used the appropriate equation (non-desert or desert) combined with the number of cooling degree-days for the location of the building. It adjusted the results with a scaling factor to account fo r the difference between the number of building operating hours assumed to derive the equations and the actua l building operating hours reported by CBECS.

The above approach provides a ‘best guess’ of the room air conditioner operating hours for a particular CBECS building. However, opera ting hours are affected by some factors not included in the analysis, such as interior heat gains from equipment or people and solar gains. To develop a range for the number of operating hours for each sample building, DOE added an error band to the value derived using the regression equa tion. The error band includes values that are ± 10% from the regression line for the appropriate building type/schedule combination.

The estimated mean number of operating hour s is 1,219 hours for the greater than 6,000 Btu/hr product class, 1,144 hours for the 8,000 to 13,999 Btu/hr product cl asses, and 1,180 hours for the greater than 20,000 Btu/hr product class.

The commercial sector operating hours were estimated based on the cooling climate in 2003. To match the residential analysis, whic h was based on 2005 climate, DOE increased the estimated commercial sector operating hours by 8 pe rcent, as given by the ratio of CDD between 2005 and 2003.

7.3.3 Variability of Room Air Conditioner Annual Energy Consumption
Figures 7.3.2 to 7.3.9 show the range of average annual energy consumption by efficiency level within the residential and commercial samples for each representative product class. The higher utilization of room air conditione rs in the commercial sector is evident in the figures.

7-10Figure 7.3.2 Range of Annual Energy Use for Residential Room Air Conditioners Without Reverse Cycle and with Louvers, Less than 6,000 Btu/h

Figure 7.3.3 Range of Annual Energy Use for Residential Room Air Conditioners Without Reverse Cycle and with Louvers, 8,000–13,999 Btu/h

7-11Figure 7.3.4 Range of Annual Energy Use for Residential Room Air Conditioners Without Reverse Cycle and with Louvers, 20,000 Btu/h or more

Figure 7.3.5 Range of Annual Energy Use for Residential Room Air Conditioners Without Reverse Cycle and without Louvers, 8,000–13,999 Btu/h

7-12Figure 7.3.6 Range of Annual Energy Use for Commercial Room Air Conditioners Without Reverse Cycle and with Louvers, Less than 6,000 Btu/h

Figure 7.3.7 Range of Annual Energy Use for Commercial Room Air Conditioners Without Reverse Cycle and with Louvers, 8,000–13,999 Btu/h

7-13Figure 7.3.8 Range of Annual Energy Use for Commercial Room Air Conditioners Without Reverse Cycle and with Louvers, 20,000 Btu/h or more

Figure 7.3.9 Range of Annual Energy Use for Commercial Room Air Conditioners Without Reverse Cycle and without Louvers, 8,000–13,999 Btu/h

7.3.4 Average Annual Energy Consumption by Efficiency Level
Tables 7.3.4 through 7.3.7 show the cons idered efficiency levels and corresponding calculated average annual energy consumption for each product class when the product is used in the residential or commercial sector.

7-14Table 7.3.4 Room Air Conditioner, Without Reverse Cycle and with Louvers, Less than 6,000 Btu/h: Average Annual Energy Use Efficiency

(IEER) Residential (kWh) Commercial (kWh)
9.52 688 640

10.1 648 604

10.6 618 575

11.1 590 549

11.6 565 526

12.0 546 508

Table 7.3.5 Room Air Conditioner, Without Reverse Cycle and with Louvers, 8,000– 13,999 Btu/h: Average Annual Energy Use Efficiency

(IEER) Residential (kWh) Commercial (kWh)
9.71 672 1181

10.3 632 1110

10.8 602 1059

11.3 576 1012
11.5 566 994

Table 7.3.6 Room Air Conditioner, Without Reverse Cycle and with Louvers, 20,000 Btu/h or more: Average Annual Energy Use Efficiency

(IEER) Residential (kWh) Commercial (kWh)

8.47 1118 3343

9.0 1052 3146

9.4 1007 3012

9.8 966 2889

10.0 947 2832

7-15Table 7.3.7 Room Air Conditioner, Without Reverse Cycle and without Louvers, 8,000–13,999 Btu/h: Average Annual Energy Use Efficiency

(IEER) Residential (kWh) Commercial (kWh)

8.43 712 1359

8.9 673 1285

9.3 644 1230

9.8 611 1167

7.3.5 Estimating Room Air Conditioner Energy Use by Month

Room air conditioner use is c oncentrated in the warm parts of the year. In conducting the LCC analysis for room air conditioners (see ch apter 8), DOE used monthly electricity prices because electricity tariffs show seasonal variation in many parts of the country. Therefore, to properly calculate room air conditioner operating co sts, DOE needed to estimate how the annual room air conditioner electricity use for each sample household is appo rtioned over the year.

To estimate electricity use by month, DOE utilized data on seasonal climate variation, as measured by cooling degree-days. RECS 2005 provides data on yearly heating and cooling degree-days for each household in the sample, but does not break this information down by month. To estimate monthly cooling degree days for the households in the RECS sample, DOE developed an approach to ma tch each household with a corresponding NOAA weather station. After matching the household to a weather sta tion location, DOE utilized the monthly coolingdegree day data from the corresponding weather st ation to estimate the percentage of household energy use per month. See appendix 7-D for more details.

7.4 CLOTHES DRYERS
DOE determined the annual energy consumption of clothes dryers by multiplying the number of cycles per year by the energy use per cycle.

7.4.1 Number of Cycles
DOE estimated the number of clothes dryer cycles per year for each sample household using data given by RECS on the number of laund ry loads washed (clothes washer cycles) per week and the frequency of clothes dryer use. Th e responses in RECS fall into one of the bins shown in Tables 7.4.1 and 7.4.2. For each ques tion, DOE assumed a uniform distribution within the boundaries of each bin and randomly assigned a value from within the appropriate range to each sample household.

7-16Table 7.4.1 Number of Loads Washed per Week Based on RECS Sample Bin Loads per Week Derived Loads per Year* Min Max 1 1 load or less 0 78 2 2 to 4 loads 78 234 3 5 to 9 loads 234 494 4 10 to 15 loads 494 806 5 More than 15 loads 806 1118

* The ranges reflect the inclusion of values in between the given bin boundaries.

Table 7.4.2 RECS Sample Clothes Dryer Usage

Bin Description Fraction of Washer Cycles When Dryer is used Min Max 1 Use it every time wash clothes 1 1

2 Use it for some, but not all, loads of wash 0.50 1

3 Use it infrequently 0.00 0.50

The responses to the above questions vary among sample households using different clothes dryer products, so they yield somewhat di fferent values for the average annual number of clothes dryer cycles for each product class (see Table 7.4.3).

Table 7.4.3 RECS Sample Clothes Dryers Utilization Product Class

Electric Standard Gas Ventless Clothes Dryer DOE Test Procedure

Assumption Clothes Washer DOE Test Procedure

Assumption Washer loads per year 301 292 268 NA 392 Clothes dryer frequency* 0.95 0.93 0.94 NA 0.84** Clothes dryer loads per year 285 271 252 416 329

* Fraction of washer loads ** Accounts for fraction of households that have a clothes washer, but no clothes dryer

7.4.2 Energy Use Calculation
For each considered efficiency level, DOE derived the field energy use by separately estimating the active mode and standby mode energy use and then adding them together. The DOE test procedure calculates active mode energy consumption by dividing the weight (lbs) of

7-17clothes dried per cycle (7 lbs for standard a nd 3 lbs for compact clothes dryers) and by the Energy Factor (EF) (lbs/kWh). f DOE adjusted the test procedure energy use to reflect field conditions by making an adjustment for clothes dr yer load weight and moisture removal factor.

For each household, DOE determined the fiel d adjustment for clothes dryer energy use during active mode by using the following formula:

avgLoadWei ght TP avgLoadWei ght RMC Field Field CD

_ EnergyUse = ∗ ( J ∗ ( J ∗ CD

_ Cycles ActiveMode ( J ( J EF avgLoadWei ght RMC TP TP

Where:

avgLoadWeight TP = average load weight in the test procedure, lbs, avgLoadWeight Field = average load weight for each household, lbs, RMC TP = remaining moisture content in the test procedure, percent, RMC Field = remaining moisture content for the household, percent, EF = efficiency of the clothes dryer during active mode, lbs per kWh, and CD_Cycles = clothes dryer cycles per year.

To assign an average load weight for e ach household, DOE developed a distribution of load weights by matching the listed tub sizes for models in the Dec. 22, 2008 California Energy Commission (CEC) directory with the correlations between tub size and average pounds in the DOE test procedure. The average load weights fo r standard-size units range from 5.1 lbs. to 10 lbs., with a mean value of 8.1 lbs. For comparison , the DOE test procedure uses a weight of 7 lbs for standard-size units.

To assign a RMC value for each household, DOE used a distribution of values based on the number of models listed at each RMC in th e Dec. 22, 2008 CEC directory. The RMC values range from 30 percent to 61 percent, with an average of 46 percent. The remaining moisture content (RMC) in the test procedure is 70 percent.

Using the above approach, DOE calculated a unique value for the clothes dryer annual active mode energy consumption for each sample household with electric clothes dryer using the number of dryer cycles specified for that household. For gas clothes dryers, DOE used a similar approach as for electric clothes dryers, but added an estimate of the energy use of electric components. An estimate of 200 kWh per cycle, which was derived from tests done by DOE, was applied for all efficiency levels except for the max-tech level. For the latter, which has a more efficient motor, the tests found a value of 187 kWh.

For each household, DOE determined the fiel d-adjusted clothes dryer energy use during standby mode by using the following formula:

f See chapter 5 for more information on how to convert from IEF to EF. IEF assumes 416 cycles, 8156 hours of standby, and a standby power that varies by efficiency level.

7-18CD Time ClothesDryerEnergyUse Standby = − CD Cycles * Standby_Power _ 60 ∗

_ J ( 8760

Where:

8760 = number of hours in one year, hrs, CD_Time = clothes dryer time to complete one cycle, min/cycle, 60 = number of minutes in one hour, min/hr, Standby_Power = standby power, kW, and CD_Cycles = clothes dryer cycles per year.

DOE assumed that clothes dryers take 60 minutes on average to complete a cycle. 6, 7, 8 Standby power varies by efficiency level as discussed in chapter 5.

For vent-less clothes dryers, DOE consider ed the impact of the dryer on the home’s heating and cooling loads. A vent-less dryer releas es heat to the surrounding environment. If the dryer is located indoors, dryer use will tend to sl ightly reduce the heating load during the heating season and slightly increase the cooling load during the cooling season. DOE believes that the effect is the same for all of the considered efficiency levels, and thus it did not include this factor in its analysis. [

7.4.3 Variability of Annual Energy Consumption
Figures 7.4.1 to 7.4.7 show the range of average annual energy consumption (active and standby mode) for clothes dryers in the household sample for each product class. :

7-19Electric Standard Average Annual Energy Use Average; Median; Box 25%-75%; Whisker: 5%-95%

0 200 400 600 800 1000 1200 1400

Level 0 Level 1 Level 2 Level 3 Level 4 Level 5 Level 6 **Efficiency Level Annual Energy Use (kWh)**  median Average

Figure 7.4.1 Range of Annual Energy Use for Vented Electric Standard Clothes Dryers

Electric Compact 120V Average Annual Energy Use Median; Box 25%-75%; Whisker: 5%-95%

0 100 200 300 400 500 600 700

Level 0 Level 1 Level 2 Level 3 Level 4 Level 5 Level 6 **Efficiency Level Annual Energy Use (kWh)**  median Average

Figure 7.4.2 Range of Annual Energy Use for Vented Electric Compact 120V Clothes Dryers

7-200 100 200 300 400 500 600 700 800

Level 0**Annual Energy Use (kWh)** Electric Compact 240V Average Annual Energy Use Median; Box 25%-75%; Whisker: 5%-95%

Level 1 Level 2 Level 3 Level 4 Level 5 Level 6 **Efficiency Level** median Average

Figure 7.4.3 Range of Annual Energy Use for Vented Electric Compact 240V Clothes Dryers

0 1 1 2 2 3 3 4 4 5 5

Level 0**Annual Gas Use (MMBtu)** Gas Average Annual Gas Use Median; Box 25%-75%; Whisker: 5%-95%

Level 1 Level 2 Level 3 Level 4 Level 5 **Efficiency Level** median Average

Figure 7.4.4 Range of Annual Gas Use for Vented Gas Clothes Dryers

7-21Gas Average Annual Electricity Use Median; Box 25%-75%; Whisker: 5%-95%

0 1 1 2 2 3 3 4 4 5 5

Level 0 Level 1 Level 2 Level 3 Level 4 Level 5 **Efficiency Level Annual Electricity Use (kWh)**  median Average

Figure 7.4.5 Range of Annual Electricity Use for Vented Gas Clothes Dryers

Ventless 240V Average Annual Energy Use Average; Median; Box 25%-75%; Whisker: 5%-95%

0 100 200 300 400 500 600 700 800 900

Level 0 Level 1 Level 2 Level 3 Level 4 Level 5 **Efficiency Level Annual Energy Use (kWh)**  median Average

Figure 7.4.6 Range of Annual Energy Use for Vent-less 240V Clothes Dryers

7-22Ventless Combination Average Annual Energy Use Median; Box 25%-75%; Whisker: 5%-95%

0 200 400 600 800 1000 1200

Level 0 Level 1 Level 2 Level 3 Level 4 Level 5 **Efficiency Level Annual Energy Use (kWh)**  median Average

Figure 7.4.7 Range of Annual Energy Use for Vent-less Combination Washer/Dryers

7.4.4 Average Annual Energy Consumption by Efficiency Level
Tables 7.4.4 through 7.4.6 present the averag e annual energy consumption by efficiency level for each considered clothes dryer product class.

Table 7.4.4 Electric Standard and Gas Clothes Dryer: Average Annual Energy Consumption by Efficiency Level

Electric Gas Integrated Energy Factor (lb/kWh) kWh/year Integrated Energy Factor (lb/kWh) MMBtu/ year kWh/year

2.96 519 2.63 1.65 71.4

3.04 504 2.71 1.60 71.4

3.10 495 2.80 1.53 71.4

3.33 461 2.97 1.45 67.9
3.35 457 2.98 1.45 63.6

3.40 445 3.02 1.45 51.6
4.52 335

-- -- --

7-23Table 7.4.5 Electric Compact Vented Dryer: Average Annual Energy Consumption by Efficiency Level

120V 240V Integrated Energy Factor (lb/kWh) kWh/year Integrated Energy Factor (lb/kWh) kWh/year

3.00 270 2.79 290

3.08 263 2.86 283
3.15 258 2.96 274

3.37 241 3.06 265

3.41 237 3.10 260
3.53 225 3.19 248
4.69 169 4.34 183

Table 7.4.6 Electric Compact Vent-less Dryer and Combination Washer/Dryer: Average Annual Energy Consumption by Efficiency Level

Compact Vent-less Dryer (240V) Combination Washer-Dryer Integrated Energy Factor (lb/kWh) kWh/year Integrated Energy Factor (lb/kWh) kWh/year

2.29 351 1.90 424

2.31 347 2.15 375

2.37 335 2.34 344

2.39 332 2.36 340
2.59 307 2.42 328
3.54 224 3.31 239

7-24REFERENCES

1. U.S. Department of Energy - Energy Information Administration, Residential Energy Consumption Survey: 2005 Public Use Data Files, 2005.

< http://www.eia.doe.gov/emeu/recs/recspubuse05/pubuse05.html >

2. U.S. Department of Energy - Energy Information Administration, Commercial Buildings Energy Consumption Survey, 2003. < http://www.eia.doe.gov/emeu/cbecs / >

3. Association of Home Appliance Manufactur ers, Trends in Energy Efficiency 2008 2008

4. American National Standards Institute & American Society of Heating, R., and AirConditioning Engineers, Inc.,, ANSI/ASHRAE 55-2004 Thermal Environmental Conditions for Human Occupancy , 2004.

5. National Renewable Energy Laboratory, National Solar Radiation Database 1991–2005 Update: User’s Manual, 2007. < http://www.nrel.gov/docs/fy07osti/41364.pdf >

6. Pescatore, P. and P. Carbone, High Efficiency, High Performance Clothes Dryer, March 31, 2005. TIAX. Report No. D0040. < http://www.osti.gov/bridge/servlets/purl/888669

­ 2VIDn8/888669.pdf >

7. Hekmat, D. and W. J. Fisk, IMPROVING THE ENERGY PERFORMANCE OF RESIDENTIAL CLOTHES DRYERS, February, 1984. LBNL. Report No. LBL-17501.

< http://escholarship.o rg/uc/item/2f3347r8 >

8. PricewaterhouseCoopers, Ecodesign of Laundry Dryers, Preparatory studies for Ecodesign requirements of Energy-using-Products (EuP) – Lot 16, June 30, 2008. CODDE. < http://www.ecodryers.org/ >

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