The British thermal unit is the amount of heat required to raise the temperature of one pound of liquid water by one degree Fahrenheit. It is heavily used in the HVAC, plumbing, and gas industries to rate the heating and cooling capacity of appliances. While technically a unit of energy, technicians frequently use it as shorthand for BTU per hour when discussing power output.
Heard on the job
That furnace puts out 80,000 BTU, which is plenty for a house this size.
Insider tip
When an HVAC tech says a unit is a 12,000 BTU air conditioner, they actually mean 12,000 BTU per hour.
Also heard as
- British thermal unit