British thermal unit – “BTU”
The British thermal unit (BTU or Btu) is a traditional unit of energy equal to about 1055 joules. It is the amount of energy needed to cool or heat one pound of water by one degree Fahrenheit. In science, the joule, the SI unit of energy, has largely replaced the BTU.
The BTU unit is most often used as a measure of power (as BTU/h) in the power, steam generation, heating, and air conditioning industries, and also as a measure of agricultural energy production (BTU/kg).[verification needed] It is still used in metric English-speaking countries (such as Canada), and remains the standard unit of classification for air conditioning units manufactured and sold in many non-English-speaking metric countries.[verification needed] In North America, the heat value (energy content) of fuels is expressed in BTUs.
- One BTU is approximately:
- 1.054 to 1.060 kJ (kilojoules)
- 0.293071 W·h (watt hours)
- 252 to 253 cal (calories, or “little calories”)
- 0.25 kcal (kilocalories, “large calories,” or “food calories”)
- 25,031 to 25,160 ft·pdl (foot-poundal)
- 778 to 782 ft·lbf (foot-pounds-force)
- 5.40395 (lbf/in2)·ft3