Kilowatt-hour (kWh)

Metric (SI)Current unit

3.6 million joules, the energy used by a 1,000-watt appliance in an hour. The billing unit for household electricity.

1 kilowatt-hour = 3,600,000 joules (exactly).

About the kilowatt-hour

Before it was a line on every power bill, the kilowatt-hour had a British nickname: the Board of Trade unit, abbreviated B.T.U. after the government body that regulated the electricity industry until 1942, when the Ministry of Power took over. In India it is still often called simply a unit, and a million of them, written MU, is a gigawatt-hour.

A kilowatt-hour is the energy of a 1 kW device running for an hour, which is 3.6 MJ, or about 3,412 British thermal units. A 100 W television watched for 10 hours uses one, and boiling a liter of water in an electric kettle takes about 0.1. In 2020 the average US household used 893 kWh a month, an average continuous draw of about 1.22 kW.

Utilities multiply the kilowatt-hours consumed by a price per kWh, and larger customers may also pay for peak demand. One common error is writing kW/h, which would mean kilowatts per hour, a rate of change of power, not energy.

Sources: Wikipedia: Kilowatt-hour; Wikipedia: British thermal unit; Wikipedia: Watt-hour

Kilowatt-hour conversion chart

1 kilowatt-hour expressed in every other energy unit:

More Metric (SI) units

• joule (energy)
• kilojoule (energy)
• megajoule (energy)
• gigajoule (energy)
• millijoule (energy)
• watt-hour (energy)
• megawatt-hour (energy)
• tonne of oil equivalent (energy)
• meter (length)
• kilometer (length)
• centimeter (length)
• millimeter (length)
• micrometer (length)
• nanometer (length)
• picometer (length)
• decimeter (length)

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