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In our modern, high-tech society, we
don't think much about some of the electronic gadgets in our
homes. Take, for example, the ever-present thermostat—a
staple of American households for decades.
It usually takes the shape of an unassuming box on the wall,
but that modest device controls the comfort of your family
on the coldest day in January and the hottest day in July.
What Is a Thermostat?
It is a temperature-sensitive switch that controls a space
conditioning unit or system, such as a furnace, air conditioner,
or both. When the indoor temperature drops below or rises
above the thermostat setting, the switch moves to the "on"
position, and your furnace or air conditioner runs to warm
or cool the house air to the setting you selected for your
family's comfort. A thermostat, in its simplest form, must
be manually adjusted to change the indoor air temperature.
General Thermostat Operation
You can easily save energy in the winter by setting the thermostat
to 68°F (20°C) when you're at home and awake, and
lowering it when you're asleep or away. This strategy is effective
and inexpensive if you are willing to adjust the thermostat
by hand and wake up in a chilly house. In the summer, you
can follow the same strategy with central air conditioning,
too, by keeping your house warmer than normal when you are
away, and lowering the thermostat setting to 78°F (26°C)
only when you are at home and need cooling.
A common misconception associated with thermostats is that
a furnace works harder than normal to warm the space back
to a comfortable temperature after the thermostat has been
set back, resulting in little or no savings. This misconception
has been dispelled by years of research and numerous studies.
The fuel required to reheat a building to a comfortable temperature
is roughly equal to the fuel saved as the building drops to
the lower temperature. You save fuel between the time that
the temperature stabilizes at the lower level and the next
time heat is needed. So, the longer your house remains at
the lower temperature, the more energy you save.
Another misconception is that the higher you raise a thermostat,
the more heat the furnace will put out, or that the house
will warm up faster if the thermostat is raised higher. Furnaces
put out the same amount of heat no matter how high the thermostat
is set—the variable is how long it must stay on to reach
the set temperature.
In the winter, significant savings can be obtained by manually
or automatically reducing your thermostat's temperature setting
for as little as four hours per day. These savings can be
attributed to a building's heat loss in the winter, which
depends greatly on the difference between the inside and outside
temperatures. For example, if you set the temperature back
on your thermostat for an entire night, your energy savings
will be substantial. By turning your thermostat back 10°
to 15° for 8 hours, you can save about 5% to 15% a year
on your heating bill—a savings of as much as 1% for each
degree if the setback period is eight hours long. The percentage
of savings from setback is greater for buildings in milder
climates than for those in more severe climates. In the summer,
you can achieve similar savings by keeping the indoor temperature
a bit higher when you're away than you do when you're at home.
But there is a certain amount of inconvenience that results
from manually controlling the temperature on your thermostat.
This includes waking up in a cooler than normal house in the
winter and possibly forgetting to adjust the thermostat (during
any season) when you leave the house or go to bed.
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