Therm (EC)
The therm (EC) is 100,000 Btu (International Table), or about 105.5 megajoules (MJ). Gas in the United Kingdom was historically billed in therms, and the EC stands for European Community, to tell it apart from the US therm.
Calories (20°C)
A Calorie (20°C) is sometimes referred to as a small calorie or gram calorie. It is a unit of energy defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius from 19.5°C to 20.5°C.