The average cost of a therm of natural gas changes on a regular basis due to fluctuating energy prices. In February 2015, for example, the average cost of a therm of utility gas was $1.087, according to the Bureau of Labor Statistics. One year previously, the price averaged $1.175.
A therm is a common unit of measurement used to communicate the cost of natural gas, as reported by the U.S. Energy Information Administration. One therm equals 100,000 BTUs (British thermal units). Many utility companies display prices based on therms, though other units of measurement are also used, such as Ccf, which equals 100 cubic feet, and Mcf (1,000 cubit feet). The letter C refers to 100 cubic feet.