A quantitative measure of electric current flow equivalent to one thousand watts being used continuously for a period on one hour; the unit most commonly used to measure electrical energy, as opposed to kilowatt, which is simply a measure of available power. Customer billings for all but the largest consumers are usually based in part or in total on the number of kilowatt-hours of electricity used. The standard unit of current flow used in physics is the joule, but since a joule is only equivalent to one watt-second, kilowatt-hour has become a much more convenient standard.

A kilowatt-hour of energy typically costs between two and twenty cents depending on where and when it is purchased and by whom. This much energy will operate a 40-watt lightbulb for a full day, a 19" color television for about four hours, a personal computer for 2-1/2 hours, an electric hairdryer for 30 to 60 minutes, an electric razor for 36 hours, a clothes dryer for 15 minutes, a microfurnace heater for 40 minutes, a clock radio for up to several days, a portable stereo for as long as a week, and a telephone answering machine for as long as a month.

While most consumers express surprise at the relatively low cost of energy for these common devices, environmental experts and energy planners alike caution that customer costs for energy in North America, which are among the lowest in the world, don't necessarily reflect the real cost of energy. Some claim that future costs of undoing any environmental damage done through most types of commercial energy generation could add dramatically to the total cost of energy over the long term.

The kilowatt-hour is the base unit for nearly all measurements of energy volume both inside and outside the energy industry, although other values are occasionally used. Related terms include:

Termtitle=watt-hour: One-thousandth of a kilowatt-hour, often used to measure the consumption of low-power Termdata=electronic devices. One watt-hour is equivalent to 3,600 joules of energy.

Termtitle=megawatt-hour (MWh): one thousand kilowatt-hours; typically enough to power several residential Termdata=blocks for a day

Termtitle=gigawatt-hour (GWH): one million kilowatt-hours; the standard unit used to measure the capacity of Termdata=transmission systems and generating facilities, and consumption levels in urban areas.

See also:

power, watt, joule