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What Is a BTU?


A BTU is the basic measurement used for rating how much energy it takes to produce heat. It’s used in determining the efficiency of air conditioning equipment, furnaces, and any appliances that heat—such as water heaters, ovens, and fireplaces. Here is what it means and how to convert BTUs into other energy measurements.

gas burners in furnace© Carolina K. Smith M.d. | Dreamstime.com

Gas burners produce significant BTUs in this furnace’s heat exchanger.

A BTU, short for British Thermal Unit, is a standardized measurement of energy. Technically, 1 BTU is roughly equal to the amount of energy required to raise 1 pound of water 1 degree F.

In North America, the BTU is used to describe both the heat content of fuels and the power of heating and cooling appliances such as furnaces, air conditioners, water heaters, stoves, fireplaces, and barbecues. When used as this type of measurement, the term “BTU” actually refers to BTUs per hour (BTU/h).

When buying a heating or cooling appliance, be sure you understand whether the stated BTU capacity refers to the unit’s input or output. An input BTU refers to the fuel used; an output BTU measures the heat (or cooling) created.

Converting BTUs to Other Energy Measurements

In some cases, it’s necessary to convert BTUs into another form of measurement. Here are a few helpful conversions:

HA2016 Central-Heating-System---Repair or Fix

• 1 BTU equals 252 to 253 calories
• 1 BTU equals .293071 watt hours
• 1 watt is approximately 3.41214 BTU hours
• 1,000 BTU hours equal approximately 293.071 watts
• 1 therm equals 100,000 BTUs
• 1 “ton” of cooling equals 12,000 BTUs per hour
• 1 standard cubic foot of natural gas yields 1,030 BTUs

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