The
kilowatt hour (symbol
kWh,
kW·h, or
kW h) is a derived unit of
energy equal to 3.6
megajoules. If the energy is being transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt-hours is the product of the
power in kilo
watts and the time in hours. The kilowatt-hour is commonly used as a billing unit for energy delivered to consumers by
electric utilities.