Therm

The therm (symbol thm) is a non-SI unit of heat energy. It was defined in the United States in 1968 as the energy equivalent of 1000 cubic feet of natural gas at standard temperature and pressure. In the US gas industry its SI equivalent is defined as exactly 100,000 BTU or 105.4804 megajoules at 59° Fahrenheit. In the European Union it was defined in 1979 as exactly 100,000 BTU and exactly 105.5060 megajoules. The unit was abolished in the United Kingdom in 1999.