This document summarizes past, current, and planned research on improving the energy efficiency of residential clothes dryers. It describes several studies conducted between 2009-2013 by organizations like PG&E, NEEA, DOE, NRDC, and CLASP that tested modifications to conventional dryers in laboratories and in homes. Key findings include that a modified conventional dryer can reduce energy use by 20%, heat pump dryers use 50-60% less energy than conventional dryers, and automatic dryer features and test procedures can significantly affect measured energy consumption. Upcoming research will test European heat pump dryer models and develop standards for commercial clothes dryers.

1. Residential Clothes Dryer Summit: Moving Forward Together
Over the past two years, energy efficiency advocates and program administrators have funded technical
research on clothes dryer energy efficiency. The table below provides a summary of past, current, and
planned research:
Research Area
Dryer
Modification
(2012-2013)
Field Study
(2011-2012)
Research Entity
The California
Statewide Codes
and Standards
Team, including
Pacific Gas &
Electric Company
(PG&E), Southern
California Edison
(SCE), San Diego
Gas and Electric
(SDG&E), and
Southern
California Gas
Company
Northwest Energy
Efficiency Alliance
(NEEA)
Description
PG&E’s technical consultant, Ecova,
modified two conventional dryers to
assess the impact on energy
consumption. Modifications included
the following:
 Adding insulation;
 Adding a heat exchanger; and,
 Re-routing the air flow;
KEY FINDINGS:
A modified conventional dryer can
reduce energy consumption by 20%.
NEEA conducted a field study on
consumer clothes dryer usage. The
study collected data from 50
households in four states.
KEY FINDINGS:
The study provides data on how
consumers in the Northwest use their
dryers, the energy consumption of
clothes dryers in the field, remaining
moisture content of clothes entering
the dryers, dryer cycle times, and the
size and nature of the clothes loads
being dried. Data indicates the number
of dryer loads per year and energy use
per load is higher than DOE and EPA
assumptions.
1
http://www.energystar.gov
Link to Results
Link1
Link2
Link3

2. Field Study
(2013-20??)
US Department of
Energy (DOE)
The Florida Solar Energy Center (FSEC)
is currently monitoring the energy
consumption of several homes in
Florida through DOE’s Building America
program. FSEC is measuring the
energy consumption of clothes dryers
and HVAC systems and replacing
equipment with higher efficiency
models as part of a phased, deep
energy retrofit project.
Field Study
(20??-2013)
The California
Investor Owned
Utilities (IOUs)
Statewide Codes
and Standards
Team
Laboratory
Testing
(2011-2012)
Collaborative
Labeling and
Appliance
Standards
Program (CLASP)
The California IOUs’ technical
consultant, Heschong Mahone Group
(HMG), conducted field testing of
commercial clothes dryers in California
and plans to release a proposal for
mandatory commercial clothes dryer
standards as part of the California Title
20 appliance standards process.
CLASP’s technical consultant, Ecova,
compared the energy consumption
and performance of North American
conventional dryers and that of
European heat pump dryers. Ecova
also assessed the impact of test cloth
that more closely resembles the type
of laundry dried in the real world.
Link4
Link5
KEY FINDINGS:
Heat pump dryers use 50 to 60% less
energy than the average conventional
dryer. Drying laundry that more closely
resembles the real world significantly
increases dryer energy consumption
and drying time.
2
3
http://www.energystar.gov
http://www.regulations.gov/contentStreamer?objectId=0900006481235b48&disposition=attachment&contentTy
pe=pdf
4
http://www.ba-pirc.org/overview/index.htm
5
http://www.clasponline.org/en/Resources/Resources/SLHeadlines/SEDI-Transforms-North-American-Market-forSuper-Efficient-Dryers

3. Laboratory
Testing
(2009-2011)
Natural Resources
Defense Council
(NRDC)
NRDC’s technical consultant, Ecova,
assessed the impact of test load
composition, fuel type, and automatic
termination on the energy
consumption of dryers.
Link6
KEY FINDINGS:
The composition of laundry
significantly increases dryer energy
consumption. In addition, a correctly
functioning automatic termination
feature substantively reduces dryer
energy consumption. Furthermore,
natural gas dryers have significantly
lower source energy and greenhouse
emissions than electric dryers.
Laboratory
Testing
(2012-2013)
Northwest Energy
Efficiency Alliance
(NEEA)
NEEA’s technical consultant, Ecova,
tested several dryers with a modified
test procedure that more closely
aligned with the type of drying
conditions identified in the NEEA field
study above. Ecova plans to conduct
additional testing on two European
heat pump dryers. One uses
supplementary electric resistance heat
and the other uses a variable speed
compressor, both of which reduce
drying time.
Link7
KEY FINDINGS:
Each dryer responded differently to
the NEEA test procedure, indicating
that it may be difficult to predict how
dryers perform in the real world using
results from the DOE federal test
procedure.
6
7
http://www.appliance-standards.org/sites/default/files/NRDC_Ecova_dryer_study_0.PDF
http://www.energystar.gov/