Btu (I.T.)
The British thermal unit (International Table), Btu (IT), is about 1,055 joules, roughly the energy needed to warm one pound of water by one degree Fahrenheit. In the United States air conditioners and furnaces are rated in Btu per hour.
Therms (UK)
The therm (UK) is a unit of heat energy primarily used in the United Kingdom to measure the energy content of natural gas. It is defined as 100,000 British thermal units (BTUs) which is approximately 105.5 megajoules (MJ).