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The British thermal unit
(BTU or Btu) is a traditional unit of energy
. It is approximately the amount of energy needed to heat one pound of water one degree Fahrenheit. One Btu is equal to about 1.06 kilojoules
. It is used in the power
and air conditioning
industries. In scientific contexts the BTU has largely been replaced by the SI
unit of energy, the joule
(J), though it may be used as a measure of agricultural energy production (BTU/kg). It is still used 'unofficially' in metric
English-speaking countries (such as Canada, the United Kingdom), and remains the standard unit of classification for air conditioning units manufactured and sold in many non-English-speaking metric countries.
In North America
, the term "BTU" is used to describe the heat value (energy
content) of fuels, and also to describe the power
of heating and cooling systems, such as furnaces, stoves, barbecue grills, and air conditioners. When used as a unit of power, BTU 'per hour' (BTU/h) is understood, though this is often abbreviated to just "BTU".
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