An acronym for KiloWatt Hour. A measure of the amount of watts of energy used. Electricity is measured in units of power called watts. Like pennies, watts are pretty small. For most purposes, electricity is measured in kilowatts, or 1000-watt units. The watt or kilowatt rating on electrical devices, such as light bulbs, tells you how much electricity it requires. The higher the rating, the more electricity it uses. The number of kilowatts used is multiplied by the number of hours of use, and the result is a kilowatt-hour or KWH. The abbreviation is often lower or mixed case, kwh, KWh or kWh.