British Thermal Unit (BTU)
The British Thermal Unit (BTU or Btu) is a traditional unit of energy equal to about 1 055.05585 joules. It is approximately the amount of energy needed to heat 1 pound (0.454 kg) of water 1 °F (0.556 °C). The term “BTU” is also used to describe the heat value (energy content) of different fuels.
Prices of different fuels and their units of measure (dollars per ton of coal, dollars per barrel of crude, cents per gallon of gasoline, cents per thousand cubic feet of natural gas) can be easily compared when expressed as dollars and cents per million BTUs.