Btu (15.6°C)
The Btu (15.6°C) specifically refers to the energy needed to raise the temperature of water from 60°F (15.6°C) to 61°F.
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.