Therm is a unit of energy measurement in the US customary system, and it is defined as the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit at a constant pressure of one atmosphere. One therm is equivalent to approximately 100,000 BTUs (British thermal units), which is a more commonly used unit for measuring energy in the United States. The term therm is often used to measure the energy consumption of natural gas or propane, as these fuels are commonly used for heating homes and buildings.
