What does therm mean?
A therm is a unit of heat or thermal energy equal to 100,000 British thermal units, commonly used in the United States when measuring or pricing natural gas. Its name suggests temperature, but a therm actually measures the quantity of energy released as heat rather than how hot something is. The unit appears in household energy bills, utility tariffs, appliance specifications, and discussions of fuel consumption. For example, a gas company may charge a set rate for each therm a customer uses during a billing period. The term is particularly associated with North American natural-gas markets, although it can be used more broadly in technical discussions of heat and energy. Knowing what a therm represents helps distinguish it from a temperature measurement, such as degrees Fahrenheit or Celsius, and from related words such as thermal and thermometer.
nounA unit of heat or thermal energy equal to 100,000 British thermal units (BTUs), used especially in the United States for measuring and pricing natural gas.
- A unit of heat or thermal energy equal to 100,000 British thermal units, used particularly for measuring and pricing natural gas.
"The gas company charged a fixed rate for each therm consumed."
"The heating bill rose because the household used more than two therms in December."
"The appliance's specifications list its energy consumption in therms per year."
The standard plural is therms, especially when stating fuel consumption or gas-billing quantities.
"The property used 18 therms last month."
A therm measures energy, not temperature: despite its name, one therm is a quantity of heat equal to 100,000 British thermal units.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does therm come from?
The English word therm comes from Greek θερμή (thermē), meaning “heat,” which is related to θερμός (thermos), meaning “hot.” The same root appears in English words such as thermal, thermometer, and thermos. In modern usage, therm developed as a practical unit for expressing the amount of heat contained in fuel, especially natural gas, rather than as a term for a temperature or a hot spring.
Related word forms
How therm is actually used
The term is especially common in North American natural-gas and utility contexts. It is technical in origin but widely understood by consumers, and it should not be confused with a measurement of temperature.
Easily confused with therm
A therm measures an amount of heat or energy, whereas a term can mean a period of time, a word, or a condition.
A therm is a unit of energy, while thermal is an adjective relating to heat or temperature.