The kilowatt-hour is a composite unit of energy equal to one kilowatt (kW) sustained for (multiplied by) one hour.

[1][2] A widely used representation of the kilowatt-hour is kWh, derived from its component units, kilowatt and hour.

It is commonly used in billing for delivered energy to consumers by electric utility companies, and in commercial, educational, and scientific publications, and in the media.

[5] This common representation, however, does not comply with the style guide of the International System of Units (SI).

[6] An electric heater consuming 1,000 watts (1 kilowatt) operating for one hour uses one kilowatt-hour of energy.

The unit price of electricity charged by utility companies may depend on the customer's consumption profile over time.

[11] While smaller customer loads are usually billed only for energy, transmission services, and the rated capacity, larger consumers also pay for peak power consumption, the greatest power recorded in a fairly short time, such as 15 minutes.

In terms of human power, a healthy adult male manual laborer performs work equal to about half a kilowatt-hour over an eight-hour day.

Megawatt-hours (MWh), gigawatt-hours (GWh), and terawatt-hours (TWh) are often used for metering larger amounts of electrical energy to industrial customers and in power generation.

The terawatt-hour and petawatt-hour (PWh) units are large enough to conveniently express the annual electricity generation for whole countries and the world energy consumption.

A higher power output will cause the battery's stored energy to be depleted in a shorter time period.

It is used to measure the daily variation of demand (e.g. the slope of the duck curve), or ramp-up behavior of power plants.

[15][16] Several other units related to kilowatt-hour are commonly used to indicate power or energy capacity or use in specific application areas.

For example, it is useful to compare the energy efficiency of household appliances whose power consumption varies with time or the season of the year.