BTU

BTU stands for British Thermal Unit, a traditional energy unit used to quantify heat. It is widely used in the United States and other parts of the English-speaking world to rate heating and cooling equipment, fuel energy content, and heat transfer. By definition, 1 BTU is the amount of heat required to raise the temperature of 1 pound of water by 1 degree Fahrenheit at standard atmospheric pressure.

In terms of energy, 1 BTU equals approximately 1,055 joules. In terms of power, heating or cooling capacity is commonly expressed as BTU per hour (BTU/h), with 1 BTU/h equal to about 0.293 watts. Conversely, 1 watt equals about 3.412 BTU/h. Larger units include the therm, defined as 100,000 BTU (roughly 29.3 kilowatt-hours). The refrigeration capacity unit, ton, equals 12,000 BTU/h, about 3.517 kilowatts.

BTU is not an SI unit; conversions are used when relating to joules, watts, or kilowatt-hours. In practical applications, devices and services are often rated in BTU/h, while energy content of fuels may be quoted in therms or BTUs. There are regional definitions and historical variants, such as BTU_IT, which can differ slightly from other definitions, so context is important for precise calculations. Overall, the BTU remains a common measure in HVAC, energy trading, and related fields.