The green line in Figure 2 represents a proposed specification/standard line that increases
efficiency stringency (CEF) with drying time. The orange dotted line represents a baseline for
vented full size electric dryers that is based on drying time and CEF data represented in
ENERGY STAR’s analysis, as well as new data that we collected.
7
The blue lines represents
EPA’s ENERGY STAR Final Draft Version 1.0 specification plus supplement for vented full
size electric clothes dryers (CEF = 3.93 and <80 minutes). For our proposal, we took this
baseline curve fit and multiplied both the intercept and coefficient to the drying time by 1.25,
representing 20 percent energy savings
8
(see Figure 2). Note that the Samsung 2013 Emerging
Technology Award winning dryer is on the trend line for conventional dryers slowed down, and
would not qualify for ENERGY STAR as proposed or our sloping line proposal.
Improved motor, more efficient blower blades, and lower pressure drop ducting inside the
dryer benefit even to the no-heat case. Our proposed criteria does not to give additional energy
use allowance for even faster drying time than typical dryers (the horizontal section of the green
line in Figure 2). To ensure that energy savings promised by a specification or standard are
preserved in day-to-day operation, it is essential to test each dryer on multiple modes. We
recommend testing the dryers in fast, medium, and slow modes, as defined below (see shaded
regions in Figure 2). Three test repetitions at each of these modes would require a total of nine
test runs.
9
This is not overly burdensome on manufacturers relative to the value of the resulting
energy savings; indeed it is the same number of tests DOE and ENERGY STAR already require
for clothes washers, where efficient models yield smaller lifetime energy savings than clothes
dryers relative to less efficient models.
Slow mode: the user manual should indicate the slow test settings. This could be an eco-
mode or the lowest available temperature that performs automatic termination. The CEF
must be greater than or equal to 5.0 and on or above the specification line (see yellow and
green shaded regions in Figure 2);
Medium mode: use the DOE appendix D2 test procedure. The CEF must be greater than
or equal to 4.0 and on or above the specification line, and less than 80 minutes (see blue
and green shaded regions in Figure 2);
Fast mode: the program selected should be the one indicated in the manual which dries
the clothing most quickly. Also, the technician should disable any energy-saving features.
The CEF must be greater than or equal to 4.0, on or above the specification line, and less
than 80 minutes. If there is no faster mode than that specified by appendix D2, the fast
test would not have to be performed (see blue and green shaded regions in Figure 2).
Proposed Tier 2 CEF Specification/standard Line for Vented Full Size Electric Dryers
Our testing, as well as that conducted and published by DOE, confirm that improved
automatic termination alone offers energy savings of roughly 17 percent and can trim
approximately five minutes off typical automatic termination cycle times. We illustrate the effect
of this improvement on Figure 3, below, highlighting the differences in energy efficiency and
7
This baseline does not include the advanced technologies of heat pump and exhaust heat exchanger.
8
20 percent energy savings corresponds to 0.8 times as much energy use. The reciprocal is 1.25 times as efficient, or
25 percent greater efficiency.
9
Alternate testing requirements could be proposed, including using more realistic clothing and varying load sizes
(see Dymond 2014, this conference).
809-©2014 ACEEE Summer Study on Energy Efficiency in Buildings