BTUs, or British thermal units, is a measurement of energy. It measures the amount of energy that is needed to heat 1 lb. of water by a single degree of Fahrenheit. It is used in a variety of industries, such as water, power, air conditioning and heating. For conversions, a single BTU is worth 1.06 kilojoules, but BTUs can also be determined by finding the number of watts that are generated from a certain machine.

Find the number of watts being output. In most cases, watts are measured in watts per hour or kilowatts per hour. If it is measured in watts per hour, multiply the number by 3,600 (60 seconds times 60 minutes) to find watts. If the measurement is kilowatts per hour, first multiply by 3,600 and then divide by 1,000 to convert kilowatts to watts. For example, consider 1 watt.

Multiply watts by 3.41. This is how many BTUs per hour are in 1 watt. By using that calculation, for the example of 1 watt, the BTUs per hour is 3.41.

Divide the number by 3,600 to convert BTUs per hour to simply BTUs. In the example of 1 watt, the BTU output is 0.0009485.