What Is a Therm?

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 roughly the energy equivalent of burning 100 cubic feet of natural gas, and is used by gas companies to determine your actual natural gas usage. The actual natural gas usage might be slightly more or less than 100 cubic feet depending on the conditions when the gas is burned, which is why therms are used as a unit. Natural gas meters measure volume and not energy content, so actual energy use is calculated by converting volume used to therms.