What word is the definition of 100,000 BTUs?

The word for 100,000 BTUs is a therm. It is a traditional unit used to measure heat energy, especially in discussions of natural gas, heating systems, and household energy consumption.

One therm equals 100,000 British thermal units, or BTUs. A BTU is approximately the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit, though the precise definition depends on the measurement convention being used. In practical energy billing, the therm is more important than the small-unit definition.

Natural-gas utilities commonly use therms when calculating customer usage. A gas bill may therefore list consumption in therms rather than showing the much larger number of individual BTUs. The unit is also used in energy-efficiency comparisons and heating-fuel calculations.

A common mix-up is confusing a therm with a thermal unit or with a tonne of refrigeration. The spelling matters: “therm” is the energy unit, while “BTU” is the smaller underlying unit. One therm is also approximately 29.3 kilowatt-hours of energy.