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Home Energy Magazine Online September/October 1999
letters
Guarantee Gets Attention
I enjoyed your article on Tucson Power Company's
Energy Cost Guarantee program ("Southwest Utility
Offers Energy Cost Guarantee," Mar/Apr '99, p. 24). However, I do have
some questions about it. First, the article didn't specify who estimates
the guaranteed energy cost for heating and cooling, and how they do it.
Do they run Elite software for each house?
Also, how do you identify the energy consumption
for heating and cooling? Is an extra meter necessary? Finally, how do you
check the thermostat setting?
Kaoru Kawamoto
Osaka Gas Company
Osaka, Japan
Author Christina Farnsworth responds:
Tucson Electric Power (TEP) uses Elite software
on each house, and it is TEP that guarantees the dollar amount of utility
usage for each house.
As stated in the article, TEP uses the months
of April and November, when there is little need for either heating or
cooling, to determine the home's baseline energy use for operating all
electric devices except those used for heating and cooling. In this way,
no extra meters are needed.
TEP relies on the homeowner's honesty rather
than on any meters or monitoring of thermostat settings. This seems to
be working, since so far TEP has had to pay back just a few dollars on
utilities for only two homes. TEP reserves the right to install meters
and monitor HVAC use should it feel that such measures are necessary. So
far, it hasn't been necessary.
Star Status for Blower Doors?
Is there an EPA or Energy Star approval or certification
for blower door tests?
Jeff Beilen
jefb@mindspring.com
Sam Rashkin, Energy Star Homes program manager,
responds:
EPA does not have an Energy Star approval
or certification for blower door tests. Rather than endorsing testing procedures,
Energy Star programs focus on labeling highly efficient products (such
as homes, appliances, equipment, lights, and so forth). The goal for the
broad range of Energy Star programs administered by the U.S. Environmental
Protection Agency and the U.S. Department of Energy is to establish Energy
Star as the symbol for energy efficiency for easy consumer decision making.
Note that blower door testing is largely addressed by the Home Energy Rating
System (HERS) industry. Effectively, every HERS rater is trained and certified
to provide blower door testing by an accredited state, regional, or national
HERS provider.
Time's Arrow Pricks the Rule of Thumb
I read your helpful magazine from cover to cover.
In an issue from last year (May/June '98), which I had forgotten under
a pile, in the article "Taking Control of Energy
Use," p. 23, there is a 3% rule of thumb about savings with set-back
thermostats. I am not a technician, but I think that you cannot obtain
a said saving for every degree Fahrenheit of setback without mention of
another important factor--isn't time, or duration, missing in the article?
To obtain 3% savings, the setback has to last for how long--eight hours?
Congratulations for your otherwise well-documented
work.
André Dupuis, Editor
Inter-mécanique du bâtiment
Montreal, Quebec, Canada
Author Lori Marsh responds:
Unfortunately, the answer is not simple. The
3% savings for every degree Fahrenheit of setback is a rough estimate that
assumes that the average temperature difference (between inside and outside
the house), which the heating or cooling system must overcome over the
entire heating or cooling season, is about 33°F. Therefore, each degree
of setback, over the entire heating/cooling season, represents a reduction
of about 3% of the total load. Obviously, the 3% rule will hold better
for some climate zones than for others. It works pretty well in 4,000-
to 5,000-heating-degree-day climates.
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