Btu (15.8°C, ISO)
The British Thermal Unit (Btu) is a traditional unit of heat, defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. The Btu (15.8°C, ISO) is a specific variant standardized by the International Organization for Standardization (ISO) based on the calorie defined at 15.8°C.
Therm (US)
The Therm (US) is a unit of heat energy commonly used in the United States, particularly in the context of natural gas consumption. It is the amount of energy equivalent to burning 100 cubic feet of natural gas and is equivalent to about 105,480,400 joules.