Power is the source or means of supplying energy. The measurement of electrical power is the measurement of the amount of work done by electrical energy. A common measure of power is horsepower, but electrical power is usually measured in Watts.
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© 2012 Consumers Energy
For most purposes, the energy used in buildings by electrical power is measured in kWh. This is how electricity is bought and sold.
Remember, a Watt (or kiloWatt) is an instantaneous measure of the level of power being expended at any one time, and a Watt-hour (or kiloWatt-hour) is a measure of the amount of energy expended over time. A useful analogy is the speedometer and odometer in an automobile. The “speedometer” could be marked in kW (how fast they are being used), and the odometer would show kWh (how many were used at the end of the trip). Much as electricity is sold by the utility to the consumer, an automobile rental is based on the total mileage driven, and not the top speed!