Lecture Seventeen Physics 100 Fall 2012 Electric Power and Energy
Watt x hour or a kilowatt-hour is a unit of energy which can be converted into a Joule.
The Watt-Hour or W·hr is a unit of energy. This makes sense because it is a unit of power (the watt) multiplied by a unit of time (an hour). If you operate a 1 watt device for 1 hour you use 1 watt-hour of energy. If you operate a 60 watt light bulb for 2 hours you have used 120 watt-hours of energy.
The kilowatt-hour (kW·hr) is also a unit of energy. It is 1000 (kilo) watt-hours. If you run a 100 watt bulb for 10 hours you use 1000 watt-hours or 1 kilowatt-hour of energy. You electric bill is typically written in terms of kilowatt-hours. A typical rate for electricity in the US is 12 to 17 cents per kilowatt-hour.
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