1 December 15, 2014 Brenda Edwards U.S. Department of Energy Building Technologies Program 1000 Independence Avenue, SW Mailstop EE-2J Washington, DC 20585–0121 RE: Notice of public meeting: Test Procedures for Residential Clothes Dryers: Docket Number EERE-2014-BT-TP- 0034 Dear Ms. Edwards: This letter comprises the comments of the Pacific Gas and Electric Company (PG&E) in response to the Department of Energy (DOE, the Department) Notice of Public Meeting: Test Procedures for Residential Clothes Dryers (Docket Number EERE-2014-BT-TP-0034). The signatory of this letter represents one of the largest utility companies in the Western United States, serving over 15 million customers. As an energy company, we understand the potential of appliance efficiency standards to cut costs and reduce energy consumption while maintaining or increasing the consumer utility of products and preserving electrical safety and grid reliability. Indeed, securing cost-effective energy savings from state and federal appliance standards is a cornerstone of our strategy to meet our customers’ energy service needs at the lowest overall cost. Clothes dryers are one of the most common white goods appliances, used in an estimated 80% of U.S. households and representing approximately 6% of total residential electricity use consumption. 1 Until very recently, energy efficiency advocates were not promoting clothes dryers as a savings opportunity because of an assumption that currently available products provided similar energy efficiency. As recently as 2009, ENERGY STAR ® best practices documentation claimed that dryers could not be awarded a label because there was little difference in energy efficiency between models. 2 However, research conducted by the Natural Resources Defense Council (NRDC), the Collaborative Labeling and Appliance Standards Program (CLASP), the Northwest Energy Efficiency Alliance (NEEA), and the California IOUs over the past five years indicates otherwise. Results demonstrate that about 15% to 50% of dryer energy use can be saved cost effectively if manufacturers adopt new technologies like advanced automatic termination and heating element modulation, users accept longer drying times for non-time critical loads, and the test procedure accurately reflects field drying conditions. 3 While we believe the DOE Uniform Test Method for Measuring the Energy Consumption of Clothes Dryers, located in 10 CFR 430 Subpart B, Appendix D2 (D2) represents significant progress in developing a robust and realistic test procedure for residential clothes dryers by more accurately measuring the energy impacts of automatic cycle termination, the IOUs still have several areas of concern regarding the representativeness of the test procedure. The 1 Residential Clothes Dryers: An Investigation of Energy Efficiency Test Procedures and Savings Opportunities, Paul Bendt, Chris Calwell and Laura Moorefield, prepared by Ecos for the Natural Resources Defense Council, November 6, 2009. 2 Energy Star (2009): Best practices, Energy Star. Available from: http://www.energy star.gov/index.cfm?c1⁄4clotheswash.clothes_washers_performance_tips. 3 Residential Clothes Dryers: An Investigation of Energy Efficiency Test Procedures and Savings Opportunities, Paul Bendt, Chris Calwell and Laura Moorefield, prepared by Ecos for the Natural Resources Defense Council, November 6, 2009; Residential Clothes Dryers: A Closer Look at Energy Efficiency Test Procedures and Savings Opportunities, David Denkenberger, Serena Mau, Chris Calwell & Eric Wanless, prepared by Ecos for the Natural Resources Defense Council, November 9, 2011. Publication of CLASP, NEEA, and California utilities’ reports is pending.
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1
December 15, 2014
Brenda Edwards
U.S. Department of Energy Building Technologies Program
1000 Independence Avenue, SW
Mailstop EE-2J
Washington, DC 20585–0121
RE: Notice of public meeting: Test Procedures for Residential Clothes Dryers: Docket Number EERE-2014-BT-TP-
0034
Dear Ms. Edwards:
This letter comprises the comments of the Pacific Gas and Electric Company (PG&E) in response to the Department
of Energy (DOE, the Department) Notice of Public Meeting: Test Procedures for Residential Clothes Dryers
(Docket Number EERE-2014-BT-TP-0034).
The signatory of this letter represents one of the largest utility companies in the Western United States, serving over
15 million customers. As an energy company, we understand the potential of appliance efficiency standards to cut
costs and reduce energy consumption while maintaining or increasing the consumer utility of products and
preserving electrical safety and grid reliability. Indeed, securing cost-effective energy savings from state and federal
appliance standards is a cornerstone of our strategy to meet our customers’ energy service needs at the lowest
overall cost.
Clothes dryers are one of the most common white goods appliances, used in an estimated 80% of U.S. households
and representing approximately 6% of total residential electricity use consumption.1 Until very recently, energy
efficiency advocates were not promoting clothes dryers as a savings opportunity because of an assumption that
currently available products provided similar energy efficiency. As recently as 2009, ENERGY STAR® best
practices documentation claimed that dryers could not be awarded a label because there was little difference in
energy efficiency between models.2 However, research conducted by the Natural Resources Defense Council
(NRDC), the Collaborative Labeling and Appliance Standards Program (CLASP), the Northwest Energy Efficiency
Alliance (NEEA), and the California IOUs over the past five years indicates otherwise. Results demonstrate that
about 15% to 50% of dryer energy use can be saved cost effectively if manufacturers adopt new technologies like
advanced automatic termination and heating element modulation, users accept longer drying times for non-time
critical loads, and the test procedure accurately reflects field drying conditions.3
While we believe the DOE Uniform Test Method for Measuring the Energy Consumption of Clothes Dryers, located
in 10 CFR 430 Subpart B, Appendix D2 (D2) represents significant progress in developing a robust and realistic
test procedure for residential clothes dryers by more accurately measuring the energy impacts of automatic cycle
termination, the IOUs still have several areas of concern regarding the representativeness of the test procedure. The
1 Residential Clothes Dryers: An Investigation of Energy Efficiency Test Procedures and Savings Opportunities, Paul Bendt,
Chris Calwell and Laura Moorefield, prepared by Ecos for the Natural Resources Defense Council, November 6, 2009. 2 Energy Star (2009): Best practices, Energy Star. Available from: http://www.energy
star.gov/index.cfm?c1⁄4clotheswash.clothes_washers_performance_tips. 3 Residential Clothes Dryers: An Investigation of Energy Efficiency Test Procedures and Savings Opportunities, Paul Bendt,
Chris Calwell and Laura Moorefield, prepared by Ecos for the Natural Resources Defense Council, November 6, 2009;
Residential Clothes Dryers: A Closer Look at Energy Efficiency Test Procedures and Savings Opportunities, David
Denkenberger, Serena Mau, Chris Calwell & Eric Wanless, prepared by Ecos for the Natural Resources Defense Council,
November 9, 2011. Publication of CLASP, NEEA, and California utilities’ reports is pending.
2
ultimate goal of any DOE test procedure is to fairly and accurately characterize the energy performance of an end-
use product in a repeatable manner. Energy efficiency test procedures and their derivative energy use estimates
should generally represent the typical or average energy performance of products in real world conditions.
Overall, we applaud the DOE for investigating test procedure revisions to more accurately capture the real-world
energy use of residential clothes dryers. As a next step, we encourage the DOE to conduct additional investigative
testing that will guide and inform the next test procedure revision, with an overarching goal of building a test that is
more representative of real-world use and better able to characterize the differences in efficiency. We believe that
the additional testing needed to adequately assess the representative energy use of a clothes dryer is quite
reasonable, considering the potential national energy savings potential from more energy efficient clothes dryers and
given the overall clothes dryer test burden is presently extremely low, relative to other appliances where the
remaining efficiency opportunities now appear to be diminishing. We note that including up to four additional tests
still involves a lower testing burden than the current DOE clothes washer energy and water test procedure.
Additionally, our analysis also suggests that repeatability would be better than the D2 test procedure alone. PG&E
and NEEA have committed to using these additional tests to qualify dryers for utility rebates.
While not having a direct impact on the test procedure, we also encourage the DOE to consider taking CO2
emissions and time-dependent valuation (TDV) into account for the forthcoming standard. We also suggest that the
DOE begin to consider and seek broader stakeholder feedback on building an integrated clothes washer-clothes
dryer test procedure.
For detailed recommendations on how to improve the DOE’s D2 test procedure, please refer to the IOUs’ March 18,
2013 and NEEA’s December 2014 forthcoming comments. The remainder of this letter will instead focus on the
results of the D2 and supplemental dryer testing conducted on behalf of NEEA and the IOUs between May and
November, 2014.
Recent National Lab Testing: A Step in the Right Direction
We are encouraged that the DOE has investigated the Association of Home Appliance Manufacturer’s (AHAM)
1992 and 2009 laundry test loads. The AHAM 1992 load in particular is composed of 100% cotton clothing articles
with a diversity of fabric thicknesses, creating a test load in which clothing articles dry at significantly different
rates. Production of this load has been discontinued, but a new order could be made. This is important for automatic
termination tests because some dryer models have sensors that are only placed at one location in the drum and may
have a biased sample of the moisture of the clothing because real word clothing tends to have greater variability of
dryness at the end of the cycle. The investigation of AHAM test loads also assessed dryer performance when drying
combined loads and with different temperature settings. Both provided useful insight into dryer performance in more
realistic settings.
However, our interpretation of the test procedure leads us to believe that the exhaust simulator should have been
placed on the natural gas dryer, which was not done in the tests performed by the Pacific Northwest National
Laboratory (PNNL). Furthermore, we feel that this investigation could have been improved by assessing dryer
performance using a more realistic test procedure as discussed in the next section. We encourage DOE to
incorporate these modifications discussed below into additional investigative testing to inform a test procedure
revision.
Supplemental Tests: Adding More Realism
In collaboration with the NEEA, we have developed four supplemental tests to the D2 test procedure (see Appendix
for test procedure language). We harmonized the test procedure with the format and language of the D2 procedure in
all sections unless we had significant reason to deviate. We created this test procedure with the objective of better
matching the test procedure to real-world conditions which allows more accurate differentiation in energy use
between dryers (which will also affect the efficiency ranking of models), while also minimizing test procedure
burden to the extent possible and providing repeatability. Our test approach also eliminates potential gaming
associated with testing clothes dryers using a single cloth composition, dryer setting configuration, and laundry load
size.
3
Since the D2 test procedure only assesses performance when drying a medium-sized laundry load with thin,
uniform, and half-synthetic test cloths, we chose a more challenging load for the supplemental tests. Developed with
industry input, our supplemental test load is composed of real clothing including socks, underwear, t-shirts, towels,
and jeans, resulting in a test load with higher cotton content. We sourced this clothing from Lands’ End, but if the
DOE wanted to increase reproducibility, it could explore the potential for having realistic clothing manufactured to
tight tolerances like the current test cloths.
We created small, medium, and large test loads to mimic the results of NEEA’s 2013 field study4 which suggested
that typical users compose laundry loads of many different sizes during everyday dryer use. While the medium size
load matches the DOE test load weight of 8.45 pounds, the small test load weighs 4.22 pounds, or half the size of the
DOE test load, and is used only in the first supplemental test. The large load weighs 16.9 pounds, twice the size of
the DOE load, and is used only in the second supplemental test. These represent reasonable departures from the
average load size in the field, which NEEA found to be 7.4 pounds. The first and second supplemental tests specify
dryer settings that are similar to those specified by the DOE except we use medium temperature, because that was
the most common temperature setting in NEEA field data. Also, if an efficient cycle setting or operating mode
(referred to as eco mode) is present in the as-shipped condition, we do not run it in eco-mode, representing the fact
that many consumers may easily disable this eco-mode. We would be open to running these tests on eco mode if the
dryer automatically defaulted back to eco, perhaps after 2 hours. This is especially true for cases where the eco mode
significantly increases drying time, which we measured as being up to three times longer than the time needed to dry
clothing using normal dryer settings.
To evaluate the savings possible from efficient mode selection, we created supplemental test three and specify a
medium-sized load of realistic clothing that is dried using the most efficient setting configuration possible. If there is
no eco-mode, we specify the lowest temperature available on a normal program. Our fourth supplemental test
specifies a medium-sized clothing load that is dried using a setting configuration that achieves the fastest rate of
drying possible, often heavy duty. We developed tests three and four to bound the range of drying speeds.
One could argue for a fifth supplemental test that assesses dry performance when loaded with a medium-sized
laundry load and configured with the normal settings specified in tests one and two. However, we believe that with
proper weighting of the D2 and four supplemental tests, we could closely approximate real-world behavior. We do
not believe the added test burden of this fifth supplemental test would provide sufficient additional information-we
can already interpolate to it.
We derived final remaining moisture content (RMC) targets through laboratory investigation, consumer
acceptability testing, and consultations with industry. We specify 4% final moisture content targets for the small,
large, and eco-mode runs. However, for the fastest run, we specify a target final moisture content of 2%,
representing the fact that many consumers in the field used the more dry setting. We specify an initial moisture
content for all supplemental tests of 62%, representing the NEEA field study average. We have used this test
procedure to test a variety of dryers, including baseline electric and gas, and a number of ENERGY STAR certified
models including two hybrid heat pumps (Emerging Technology Award winners), and a European pure heat pump.
Figure 1 shows the D2 combined energy factor (CEF: pounds dried per kWh) and utility combined energy factor
(UCEF) of the dryers we tested with all five runs weighted equally. We are open to adjusting these weighting factors
based on field data. ENERGY STAR and even the EPA Emerging Technology Award (ETA) (hybrid heat pumps
with supplemental electric resistance heating) dryers are only marginally better than conventional dryers by this
metric. However, there is significant room for improvement because the European (pure heat pump) dryer test
shows significantly better efficiency than any of the other electric dryers tested. When the performance of gas and
electric dryers are compared on a site energy basis, a gas dryer does not appear to perform as well as an electric
dryer because losses associated with electricity generation for electric dryers are ignored. The general trends are
similar to the D2 test, but the rank orders change significantly. This shows that it is not possible to do a simple
correction factor from a D2 result to the UCEF. The failed runs (not low enough final RMC) are included in the
average, though these runs could be given zero values to provide incentive for manufacturers to maintain consumer
satisfaction.
Figure 1. Utility Combined Energy Factor (UCEF, average of CEF values achieved during supplemental tests one
through four and DOE D2) (light purple, green, red, and blue) and D2 CEF values (dark purple, green, red, and
blue).5 The number of runs failed per dryer (target remaining moisture content not reached even when drying under
maximum dryness settings) is signified by the number of stars to the left of the bar.
Figure 2 shows the annual CO2 emissions from the different dryers. These CO2 generation estimates were made
using the EPA emission calculator values.6 In this case, the losses of electricity generation are fully accounted for
and the gas dryer performs best, significantly better than even the European heat pump. Since the other dryers are all
electric, the relative ranking stays the same among them.
5 One test for each of D2, small, large, eco, and fast runs was performed for each dryer – all on a single unit. 6 EPA, Greenhouse Gas Equivalencies Calculator. http://www.epa.gov/cleanenergy/energy-resources/calculator.html#results
Utility Combined Energy Factor and D2 Values of all Dryers Tested (Ordered by UCEF Values)
European Heat Pump
Emerging Tech Dryers
ENERGY STAR Dryer
Baseline Electric Dryers
Baseline Gas Dryer
* One failed run ** Two failed runs
*
*
**
*
*
D2 Value UCEF
D2 Value UCEF
D2 Value UCEF
D2 Value UCEF
D2 Value UCEF
5
Figure 2. CO2 emissions per year for European heat pump, emerging technology, ENERGY STAR, baseline electric,
and baseline gas dryers.
Figure 3 shows the run-to-run variability between the D2 test and the four supplemental test runs on a single
Emerging Technology Award dryer tested. There is a significant difference in both time and CEF between the D2
and supplemental tests, and among supplemental tests (different load sizes and dryer settings). This highlights the
need for high efficiency levels across a variety of conditions, instead of just for the D2 test scenario.
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
CO2 Gas Annually (metric tons)
CO2 Gas Annually (Metric Tons)
European Heat Pump
Emerging Tech Dryers
ENERGY STAR Dryer
Baseline Electric Dryers
Baseline Gas Dryer
6
Figure 3. CEF versus drying time for all tests run on one of two emerging tech dryers.
Figure 4 - Figure 8 show the CEF results as a function of drying time from all dryers tested on each of the five
different tests (DOE D2 and supplemental tests one through four). In Figure 3, one conventional dryer appears to
meet the applicable ENERGY STAR Version 1.0 CEF requirement.
1
2
3
4
5
0 10 20 30 40 50 60 70 80 90 100 110 120 130
CO
MB
INED
EN
ERG
Y F
AC
TOR
(C
EF)
DURATION (MIN)
Emerging Tech Dryer #1 Run Time vs. CEF Values
D2SmallLarge"Eco""Fastest"
Emerging Tech Award "Worst Case" Setting CEF ≥ 3.73
Emerging Tech Award Normal Setting CEF ≥ 4.3
EPA ENERGY STAR CEF = 3.93
7
Figure 4. CEF versus drying time for all dryers tested using DOE D2 test protocol based on one test per data point.
Figure 5 shows small load CEFs versus drying times. The hybrid heat pumps actually had lower efficiency than
several of the conventional dryers. This may be due to the fact that a significant amount of electric resistance heating
is used in the beginning of the runs, and since the small load runs are shorter, the runs are composed of a greater
overall fraction of electric resistance heating. However, this does not have to be the case, because the European heat
pump does not have any electric resistance. The European heat pump is more efficient than any of the conventional
dryers, but the margin is relatively small.
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80
CO
MB
INED
EN
ERG
Y F
AC
TOR
(C
EF)
DURATION (MIN)
D2 Run Time vs. CEF Values
European HPEmerging Tech DryersENERGY STAR DryerBaseline DryersBaseline Gas Dryer
Emerging Tech Award "Worst Case" Setting CEF ≥ 3.73
Emerging Tech Award Normal Setting CEF ≥ 4.3
Emerging Tech Award "Best Case" Setting CEF ≥ 5.3
EPA ENERGY STAR CEF = 3.93
8
Figure 5. CEF versus duration for all dryers tested using supplemental test one (small, 4.2 lb test load with normal
dryer settings).
Figure 6 shows the CEFs and drying times for all dryer testing conducted using supplemental test two (large, 16.9
pound supplemental load, normal dryer settings). One Emerging Technology Award dryer did not perform as well as
some of the conventional dryers. Drying times are significantly longer, as expected.
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80 90 100
CO
MB
INED
EN
ERG
Y F
AC
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(C
EF)
DURATION (MIN)
Small Run Time vs. CEF Values
European HP
Emerging Tech Dryers
ENERGY STAR Dryer
Baseline Dryers
Baseline Gas Dryer
Emerging Tech Award "Worst Case" Setting CEF ≥ 3.73
Emerging Tech Award Normal Setting CEF ≥ 4.3
Emerging Tech Award "Best Case" Setting CEF ≥ 5.3
EPA ENERGY STAR CEF = 3.93
9
Figure 6. CEF versus duration values for all dryers tested using supplemental test two (large, 16.9 lb supplemental
test load, normal dryer settings).
Figure 7 shows the CEFs and drying times for all dryers testing using supplemental test three (medium, 8.45 pound
supplemental test load, efficient dryer settings). The Emerging Technology Award and ENERGY STAR dryers were
less efficient than several conventional dryers. This finding is particularly concerning and has the potential to lead to
significant confusion in the marketplace if energy efficient dryers, tested in the most energy efficient mode, are
actually yielding no savings for customers when used with a realistic load.
1
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3
4
5
6
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0 20 40 60 80 100 120 140 160 180
CO
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INED
EN
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(C
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DURATION (MIN)
Large Run Time vs. CEF Values
European HPEmerging Tech DryersENERGY STAR DryerBaseline DryersBaseline Gas Dryer
Emerging Tech Award "
Worst Case" Setting CEF ≥ 3.73
Emerging Tech Award Normal Setting CEF ≥ 4.3
Emerging Tech Award "Best Case"
Setting CEF ≥ 5.3
EPA ENERGY STAR CEF = 3.93
10
Figure 7. CEF versus duration values for all dryers tested using supplemental test three (medium, 8.45 lb
supplemental test load, efficient dryer settings).
Figure 8 shows the CEFs and drying times for supplemental test four (medium, 8.45 pound supplemental test load,
fastest drying settings). One of the Emerging Technology Award dryers and the ENERGY STAR certified dryer
performed worse than several conventional dryers.
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
CO
MB
INED
EN
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Y F
AC
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(C
EF)
DURATION (MIN)
"Eco" Run Time vs. CEF Values
European HP
Emerging Tech Dryers
ENERGY STAR Dryer
Baseline Dryers
Baseline Gas Dryer
Emerging Tech Award "Worst Case"
Setting CEF ≥ 3.73
Emerging Tech Award Normal Setting CEF ≥ 4.3
Emerging Tech Award "Best Case" Setting CEF ≥ 5.3
EPA ENERGY STAR CEF = 3.93
11
Figure 8. CEF versus drying time for all dryers tested using supplemental test four (medium, 8.45 lb supplemental
test load, “fastest” drying settings).
Overall, performance on the realistic tests was significantly different than the D2 tests. Not only was the rank order
of efficiency changed within a category, but in many cases, supposedly more efficient dryers were actually less
efficient than conventional dryers under some test conditions. This demonstrates the critical importance of testing
dryers with realistic clothing under a variety of settings and load sizes, all of which are encountered in the field. For
most dryers, the difference in CEF and drying time is greater for the different load sizes than for the different
settings. However, dryers may behave differently in the future, so we believe it is still important to test different
settings.
Repeatability
We have calculated the variation7 based on a number of repeat tests across all the dryers.
8 Table 1 shows the
variation for each of the five tests. In three out of the four supplemental tests, the variation is actually less than the
D2 test.
Table 1. Variation for DOE D2 test and each Supplemental test.
Test D2 Small Large Eco Fast
Variation 5.1% 5.4% 2.8% 3.0% 2.3%
Number of data
points
25 6 8 17 5
7 Coefficient of variation, i.e. the standard deviation (SD) divided by the mean. 8 Some of the repeat tests went out of tolerance for environmental controls for a limited amount of time, but the average value
over the run was always in tolerance. If anything, this overstates the variability and applies equally to D2 and supplemental tests,
so the comparison between D2 and supplemental tests is still valid.
1
2
3
4
5
6
7
0 10 20 30 40 50 60 70 80 90 100 110 120
CO
MB
INED
EN
ERG
Y F
AC
TOR
(C
EF)
DURATION (MIN)
"Fastest" Run Time vs. CEF Values
European HPEmerging Tech DryersENERGY STAR DryerBaseline DryersBaseline Gas Dryer
Emerging Tech Award "Worst Case" Setting CEF ≥ 3.73
Emerging Tech Award Normal Setting CEF ≥ 4.3
Emerging Tech Award "Best Case" Setting CEF ≥ 5.3
EPA ENERGY STAR CEF = 3.93
12
In order to calculate the overall variation in the UCEF, we use the conventional method of adding variations.9
Generally, adding more tests reduces the percent variation in the average CEF. Even when starting with the variation
of the DOE value, adding the greater variation of the small realistic test still decreases the variation in the average
CEF (see Table 2). Then as more realistic tests are added, the uncertainty in the UCEF falls even further.
Table 2. Variation for suites of tests.
Test suite D2 D2 + 1 realistic D2 + 2 realistic D2 + 3 realistic D2 + 4 realistic
Variation in
average CEF
5.1% 3.7% 2.6% 2.1% 1.8%
This analysis shows that with the four supplemental tests, the overall repeatability is better than with the single DOE
D2 test.
The current testing burden for dryer manufacturers is a single DOE D2 test per unit.10
Our proposal is to add four
supplemental tests, for a total of five tests. While this would increase the overall number of tests, we believe
additional testing is both justified and necessary based on laboratory tests that have uncovered significant changes in
relative energy use when a clothes dryer is tested with loads that will be more realistic of actual customer use.
Additionally, the additional testing would still be significantly less than the test burden required for a clothes
washer.
We do not yet have data on reproducibility to characterize the variation between test labs. Therefore, we recommend
that the DOE repeat some of these tests to assess reproducibility. However, we note that both the D2 and the
supplemental tests would have added variation due to differences in test labs and dryer units (within the same
model). Even if there is greater variation between batches of clothing associated with realistic clothing, the overall
repeatability of the average CEF could be better with realistic clothing because of the better repeatability. Even if
overall repeatability with realistic clothing is not as good as the D2 test procedure, the added accuracy (see NEEA
comment letter December 15, 2014) of the realistic tests is well worth the small increase in variation.
Because this test procedure more closely mimics behavior in the real world, it should also more accurately capture
the real-world savings of technologies that have not yet been commercialized, such as exhaust heat exchangers.
Additional recommendations
We encourage DOE to enable comparison of dryers by incorporating the use of CO2 emissions and TDV as metrics
of comparing dryers.
Natural gas represents an interim technology step, especially in new construction, that produces similar amounts of
CO2 emissions as today’s heat pumps, but is more cost-effective and enables faster drying time. TDV could
recognize dryers that move electrical consumption off peak.
We encourage the DOE to begin to consider an integrated washer-dryer test procedure.
Using the same realistic clothing load we developed for the dryer test procedure would provide additional data on
real-world washer performance. Furthermore, manufacturer test burden can actually be reduced because the clothing
could go directly from the washer to the dryer, avoiding the labor-intensive step of wetting the clothing for the dryer
to tight tolerances. Also, synergies between the washer and dryer in terms of energy efficiency and cycle time could
be better understood.
9 SDtot
2 = SD12 + … + SDn
2
10 For certification, two or three units of the same basic model must be tested.
13
Conclusions
To summarize, we encourage DOE to build on its recent work and test dryers with a variety of load sizes, settings,
and clothing compositions. Although increased, the energy testing burden would be less than what manufacturers
encounter when testing and certifying clothes washers to DOE, and the repeatability may be better than the current
D2 test procedure. The rank order of the efficiency of dryers changes significantly when using realistic clothing of
different load sizes and settings. Therefore, the supplemental testing is critical to determine real-world energy
savings of dryers. With industry vetting and anticipated use for utility rebate programs, supplemental tests one
through four of the NEEA / PG&E Utility Test Protocol are well-positioned to supplement the existing D2
procedure. Considering CO2 and TDV would also make for a more fair comparison between dryer technologies and
combining the washer and dryer test procedures would enable even more realism. We are grateful for the
opportunity to submit these comments and look forward to engaging further with DOE in the effort to improve the
energy efficiency of clothes dryers.
Sincerely,
Patrick Eilert
Principal, Codes and Standards
Pacific Gas and Electric Company
14
APPENDIX: SUPPLEMENTAL TEST PROCEDURE LANGUAGE
Utility Test Protocol for Residential Clothes Dryers Combined Supplemental and DOE D2 Test Procedures
Developed by ECOVA on behalf of NEEA and PG&E
Version 0.05
The Northwest Energy Efficiency Alliance (NEEA) and Pacific Gas and Electric (PG&E)
commissioned Ecova to expand on the U.S. Department of Energy’s (DOE) new residential
clothes dryer test procedure, Uniform Test Method for Measuring the Energy Consumption of
Clothes Dryers - Appendix D2, to include a wider range of drying modes and settings, and a
more diverse and challenging test load of mostly 100% cotton garments. This new, expanded
group of dryer tests, finalized in August of 2014 and named the Utility Test Protocol, produces a
final Utility Combined Energy Factor (UCEF). The UCEF is a weighted average the five
combined energy factors (CEF) calculated from the results of the five tests described in this
protocol.
NEEA and PG&E worked with Ecova to develop the Utility Test Protocol because the DOE’s
Appendix D2 only assesses dryer performance in a single mode with a uniform test load
composed of thin, half synthetic test cloths. NEEA collected field data showing that real world
dryer operation was significantly different, with consumers drying clothing loads of varying size,
cotton content, and clothing dimensionality under multiple dryer modes. The supplemental tests
more fully account for real world use conditions by testing dryers in a variety of operational
modes with a test load composed of realistic test articles. At this point, the supplemental tests are
only for full-sized dryers with automatic termination capability.
Appendix D2 was designed to assess dryer performance during auto-terminating operation with a
uniform test load and was added to Subpart B of Code of Federal Regulations Part 430, Uniform
Test Method for Measuring the Energy Consumption of Clothes Dryers on August 13th
, 2013.
NEEA and PG&E modeled the Utility Test Protocol after Appendix D2 to ensure consistency of
approach as much as possible, making it possible for laboratory technicians already familiar with
Appendix D2 to carry out the Utility Test Protocol without the need for new equipment or
retraining. This protocol remains largely unchanged from Appendix D2 in Sections 1 to 2.5 and
Sections 3.5 to 4.8. Sections 2.6, 2.7 and 3.4 were modified with additional language for the new
test loads, and Sections 3.3 and 4.9 for additional tests runs and post data processing.
These tests shall be performed on an individual unit (unit-to-unit variation does not need to be