Converters
Convert power between watts, kilowatts, horsepower, and BTU per hour.
Enter your numbers to see the answer.
Power converter guide
The power converter relates watts, kilowatts, horsepower, and BTU per hour, the four units that appear on motor plates, generator labels, heater boxes, and air-conditioner specifications. Power is energy per unit time; the SI unit, the watt, is one joule per second. Horsepower here is the mechanical (imperial) horsepower of exactly 550 foot-pounds-force per second, which works out to 745.699872 W; the metric horsepower (PS) used for European car engines is a slightly smaller 735.49875 W. BTU per hour is a heating and cooling rate: 1 BTU/h is 0.29307107 W, so 1 kW is 3,412.14 BTU/h. Everything runs through watts. Use it to compare a heater rated in BTU/h with one rated in kW, size a generator for a motor listed in horsepower, or read a European datasheet in kW. Power is not energy: a rating in kW says how fast a device uses energy, and the electricity bill charges for kWh, which is power multiplied by hours.
Power (to) = power (from) × watts per from-unit ÷ watts per to-unit. Factors (W): watt 1, kilowatt 1,000, horsepower 745.699872, BTU/h 0.29307107.
Worked example with the defaults: 1,000 watts to kilowatts. Divide by the watts in a kilowatt: 1,000 ÷ 1,000 = 1 kW, the displayed figure. The detail rows give the same power as 1,000 ÷ 745.699872 = 1.34 hp and 1,000 ÷ 0.29307107 = 3,412.14 BTU/h. A 12,000 BTU/h air conditioner (one refrigeration ton) is 12,000 × 0.29307107 = 3,516.85 W, or 3.52 kW. A 150 hp engine is 150 × 745.699872 = 111,854.98 W, which the kW option shows as 111.85 kW.
Enter the rating as a decimal in W, kW, hp, or BTU/h. Milliwatts divide by 1,000 to watts; megawatts multiply by 1,000 to kilowatts. The hp option is mechanical horsepower (745.7 W); for a metric-horsepower (PS or CV) figure multiply by 0.98632 first, and for boiler horsepower (9,809.5 W) use watts. “BTU” on an appliance box always means BTU per hour. Refrigeration tons are 12,000 BTU/h each and are covered by the AC cooling capacity converter.
Unit conversion is exact when the conversion factor is exact, so the only real uncertainty here is rounding and the precision of your input. Where a unit has more than one definition — US versus imperial measures, or short versus metric tons — the wrong variant produces a plausible-looking but wrong answer. The units note above states which definition this page uses. On this page the figure rests entirely on value, from and to, so start there if the power converter returns something you did not expect.
Good to know: kW and kWh are different quantities. A 2 kW heater draws 2 kW; running it for 3 hours uses 6 kWh, and this tool converts only the first. An appliance’s electrical input in watts is not its heating or cooling output in BTU/h once efficiency enters: a heat pump can deliver 3 kW of heat from 1 kW of electricity. Car horsepower figures may be SAE net, DIN, or PS, which differ by a few percent, and this converter does not adjust for that.
Conversion results use stated mathematical factors and display precision. For regulated, medical, engineering, or contractual work, confirm the required standard and precision.
Sources
How it works
Convert power between watts, kilowatts, horsepower, and BTU per hour. This tool explains the calculation so you can adjust the assumptions to match your situation.
Worked example
With Value = 1000 · From = W · To = kW → 1 kW (1,000 W converted to kW). Change an input above and this example updates with your numbers.
Common questions
One mechanical horsepower is 745.7 W (exactly 745.699872 W, from 550 ft·lbf/s). So 100 hp is 74.57 kW and 1 kW is 1.341 hp. A metric horsepower (PS) is 735.5 W, so a 300 PS engine is 295.9 hp.
Multiply by 3,412.14; 1 kW = 3,412.14 BTU/h because 1 BTU/h = 0.29307107 W. A 5 kW heater is 17,060.71 BTU/h. Going the other way, divide BTU/h by 3,412.14, so a 12,000 BTU/h unit is 3.52 kW.
Yes. Kilo means one thousand, so 1,000 W = 1 kW, 1,500 W = 1.5 kW, and 1,000,000 W = 1 MW. The converter shows 1,000 W as 1 kW, 1.34 hp, and 3,412.14 BTU/h, all the same rate of energy use.
A kilowatt is a rate, like speed; a kilowatt-hour is an amount, like distance. A 1.5 kW kettle boiling for 4 minutes uses 1.5 × 4 ÷ 60 = 0.1 kWh. Utilities bill kWh; this page converts kW.
12,000 BTU/h, or 3.52 kW, the rate needed to melt one short ton of ice in 24 hours. A 2-ton unit is 24,000 BTU/h or 7.03 kW, and a 3-ton unit is 36,000 BTU/h or 10.55 kW.