Watts to BTU per hour Converter

The watt is the SI unit of power: one joule of energy transferred each second. Its symbol is W, and it is the base from which every larger power unit is built.

Watt ratings appear on light bulbs, televisions, kettles, solar panels, inverters and small generators. Physics and engineering use the watt for every rate of energy transfer, from a laser to a motor.

Because power is a rate and energy is an amount, a watt multiplied by a duration gives energy in joules or watt-hours. Metric steps above the watt are exact powers of one thousand.

A frequent error treats the watt as a quantity of energy, so an appliance rating is read as consumption. Power needs a time period before it becomes an amount of energy.

Watts suit appliance and electronics figures, kilowatts suit generators, inverters and solar arrays, and megawatts suit grid capacity. Milliwatts cover indicator lights and small sensors. Reading a generator rating in watts rather than kilowatts multiplies the number by a thousand and misstates the scale.

One BTU per hour is exactly 0.29307107017222 watts, because one BTU is exactly 1,055.05585262 joules and an hour holds 3,600 seconds. The symbol is BTU/h.

Air conditioners, heat pumps, furnaces and chillers are rated in BTU per hour, and the figure on a room air conditioner describes its cooling capacity. Heating and cooling engineering uses the same unit for equipment sizing.

BTU per hour measures a rate, so it must be multiplied by a duration to produce an energy amount. Converting it to watts uses the exact factor, and 12,000 BTU per hour works out to about 3.5 kilowatts.

Treating BTU per hour as a unit of energy is a common error, since the same letters without the time element name an amount. A capacity rating and a consumption figure are therefore different quantities.

Cooling and heating capacities are quoted in BTU per hour, the electrical draw of the same equipment is quoted in kilowatts, and its motor may be quoted in horsepower. Choosing the wrong sibling changes the number by a factor of more than three.