| This page will lead
you through the process of figuring out how much
a specific appliance is costing you for a specific
amount of time. If some of the words are unfamiliar
to you, you might want to look at the list of
helpful terms.
STEP ONE • Determine the wattage
of the appliance
Since the wattage of a machine determines the
electrical usage per hour, the first thing to
do is to find out the wattage. Look at the serial
plate of the appliance to get this information.
If the serial plate doesn't list watts, you can
multiply volts times amps to get watts.
STEP TWO • Calculate kilowatt hour
use of the appliance
This step requires you to do some math. Or, if
you'd like, you can use our calculator
for this step.
The basic formula to find kilowatt hour use is:
kWh use = watts x hours / 1000
| Example
A: |
A light uses 100 watts and is left on
15 hours. How many kWhs are used?
kWh use = (100 watts x 15 hours) / 1000
= 1.5 kWh |
|
Example B:
|
A microwave oven uses 1,450 watts and you
use it for 30 minutes. How many kWhs are
used?
kWh use = (1,450 watts x 0.5 hours) / 1000
= 0.725 kWh
|
|
Example C:
|
A 1/2 horsepower motor on a ventilation
fan operates for 8 hours. How many kWhs
are used?
kWh use = 1 kW per HP x 0.5 HP x 8 hours
= 4.0 kWh
|
STEP THREE • Calculate average
cost of a kilowatt hour
Get out your last electric bill and divide your
electric bill by the number of kilowatt hours
you used. This will give you an average cost per
kilowatt hour. Average kWh cost = $ amount of
bill kWh used Example: $96 bill 1200 kWh = $0.08
per kWh
STEP FOUR • Find the cost of the appliance
Using the information that you found in steps
2 and 3, you can calculate the cost of the use
of the appliance as you specified in step 2.
| Example
A: |
The cost of the use of the light = 1.5
kWh x $0.08 = $0.12 = 12 cents |
|
Example B:
|
The cost of the use of the microwave = 0.725
kWh x $0.08 = $0.058 = 5.8 cents
|
|
Example C:
|
The cost of the use of the motor = 4.0 kWh
x $0.08 = $0.32 = 32 cents
|
HELPFUL TERMS • Some
electrifying words to know
| Watt: |
W |
A basic unit of electrical
power used for measuring work done. |
| Kilowatt: |
kW |
1,000 watts Megawatt (MW) 1,000 kilowatts
or 1 million watts. |
| Kilowatt Hour: |
kWh |
A unit of work or energy equal to using
1,000 watts for one hour. Your bill is computed
according to the number of kWhs that you
use. |
| Horsepower: |
h.p. |
A unit equal to 746 watts. Usually used
to measure the power of motors. |
| Ampere: |
Amp. |
The measure of current flowing through
a wire. |
| Voltage: |
Volt |
The force which moves electric current
through a conductor from the origin to the
point of use. |
|
