The Energy Story
The Energy Problem
The Energy Solution
Conserving
Electricity
Appliance
Efficiency
Renewable
Energy |
Conserving
Electricity
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When
you look on most of the appliances in your home, you will
see several numbers, including the volts (v), hertz (hz),
and the watts (w). Sometimes you may have to look in the manual
that came with that appliance to find these numbers. The main
number we need to figure out the energy that that appliance
uses is the watts, which is a unit of power.
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What is Power?
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The unit
for measuring energy in the metric system is the Joule (J)
or a newton meter (N m). The equations for various kinds of
energy yield joules, for example:
In order
to determine the energy used by an appliance, you also need
to know how long, or the time, that it was turned on. The
unit of the watt is a unit of power, or the energy used per
time. The equation for power is:
The unit
of a joule of energy is a very small amount of energy and
therefore the watt is a very small amount of power. While
many appliances are rated in watts, it is common to see power
measured in kilowatts (kw) or thousands of watts.
Rating
Your Appliance
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The electric
company actually bills you for the amount of energy that you
use. But your appliances are rated by the amount of power
that they use. You can easily find the amount of energy used
by solving the power equation for energy. You get:
Now
you can plug in the power in watts that you found on your
appliance and the time in hours. When you do that, the units
come out to be kilowatt hours (kw hr). While you could convert
the units into joules, it has become customary to leave the
energy in the units of kilowatt hours.
Now
all you need to know is how much your electric utility or
company charges you for energy. This will usually be in the
units of $ per kw hr. Then you just multiply the kw hrs by
the $ per kw hr, and you end up with the cost for that appliance
for the amount of time that you have used it.
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