With that being said, have you ever wondered what exactly a therm is? When researching companies and plans in your area, the term "therm" is most often associated with the published price, as in price per therm. A therm is a unit for quantity of heat that equals 100,000 British thermal units (BTU). A BTU is an amount of energy needed to raise one pound of nearly frozen water (39 degrees Fahrenheit) by one degree Fahrenheit. A therm is equal to 100 cubic feet of natural gas, and is used by gas companies to determine your actual natural gas usage.