BTU (British Thermal Unit)
A traditional unit of heat energy, approximately the energy needed to heat one pound of water by one degree Fahrenheit. One kWh equals about 3,412 BTU. Used to rate furnaces, water heaters, and heating/cooling systems.
Why It Matters
Furnace and water heater ratings use BTU, so understanding this unit helps compare gas vs electric appliances and estimate fuel costs.
Related Terms
kWh (Kilowatt-hour)
A unit of energy equal to 1,000 watts used for one hour. This is how utilities measure your electricity usage.
Therm
A unit of heat energy equal to 100,000 BTU. Natural gas bills for residential customers are typically measured in therms. One therm is roughly equivalent to 100 cubic feet (1 Ccf) of natural gas.
MMBtu (Million British Thermal Units)
A unit of energy commonly used to price natural gas. One MMBtu equals approximately 1,000 cubic feet of natural gas. U.S. natural gas prices are typically quoted in dollars per MMBtu.