Btu (15°C)
The Btu (15°C) is a specific variant of Btu to reflect the energy needed to raise the temperature of water at 15 degrees Celsius by one degree.
Therm (EC)
The Therm (EC) is a unit of energy primarily used in the United Kingdom for billing purposes in the gas industry. It is defined as 105.5 megajoules (MJ). The "EC" in Therm (EC) stands for European Community as it was created to standardize within European countries.