Electricity is measured in units of power called watts. It
was named to honour James Watt, the inventor of the steam
engine. One watt is a very small amount of power. It would
require nearly 750 watts to equal one horsepower. A kilowatt
represents 1,000 watts. A kilowatt-hour (kWh) is equal to
the energy of 1,000 watts working for one hour. The amount
of electricity a power plant generates or a customer uses
over a period of time is measured in kilowatt-hours (kWh).
Kilowatt-hours are determined by multiplying the number of
kW's required by the number of hours of use. For example,
if you use a 40-watt light bulb 5 hours a day, you have used
200 watts of power, or .2 kilowatt-hours of electrical energy.