Other Energy-related Units
Several other units are commonly used to indicate power or energy capacity or use in specific application areas. All the SI prefixes may be applied to the watt-hour: a megawatt hour is 1 million W·h, (symbols MW·h, MW h) a milliwatt hour is 1/1000 W·h, and has the symbol mW·h or mW h, and so on.
Average annual power production or consumption can be expressed in kilowatt hours per year; for example, when comparing the energy efficiency of household appliances whose power consumption varies with time or the season of the year, or the energy produced by a distributed power source. One kilowatt hour per year equals about 114.08 milliwatts applied constantly during one year.
The energy content of a battery is usually expressed indirectly by its capacity in ampere-hours; to convert watt hours (W·h) to ampere hour (A·h), the watt hour value must be divided by the voltage of the power source. This value is approximate since the voltage is not constant during discharge of a battery.
The Board of Trade unit (BOTU) is an obsolete UK synonym for kilowatt hour. The term derives from the name of the Board of Trade which regulated the electricity industry until 1942 when the Ministry of Power took over. The B.O.T.U. should not be confused with the British thermal unit or BTU, which is a much smaller quantity of thermal energy. To further the confusion, at least as late as 1937, Board of Trade unit was simply abbreviated BTU.
Burnup of nuclear fuel is normally quoted in megawatt-days per tonne (MW·d/MTU), where tonne refers to a metric ton of uranium metal or its equivalent, and megawatt refers to the entire thermal output, not the fraction which is converted to electricity.
Read more about this topic: Kilowatt Hour
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