Power Converter
Convert watts, kilowatts, horsepower, BTU/h, and more.
- watts
- kw
- hp
- horsepower
- power
About Power Converter
Power is the rate at which energy is used or produced — energy per unit of time. Watts are the SI unit (one joule per second), but in everyday use power shows up in a confusing tangle of named units: kilowatts on power-station nameplates, horsepower on car engines and boat motors, BTU per hour on air conditioners and furnaces, and tons of refrigeration in commercial cooling.
To make it worse, "horsepower" itself comes in flavours — mechanical (the original imperial definition, ~745.7 W) and metric (PS, ~735.5 W) — which causes specs from different markets to disagree by a couple of percent. This converter handles the common power units side by side so you can compare a heat-pump rating in BTU/h with a generator rating in kilowatts without doing the arithmetic in your head.
How to use
Enter a power value and pick its unit — watts, kilowatts, megawatts, horsepower (mechanical), metric horsepower (PS), BTU per hour, foot-pounds per second, and more. The conversions panel lists the equivalent in every other unit.
Tap a row to switch the input to that unit, or use the copy button on any row to lift just its value. Useful for sizing HVAC equipment, comparing engine outputs across regions, or sanity-checking solar-panel or generator specs.
Frequently asked questions
How many watts is one horsepower?
One mechanical horsepower (the original imperial definition) is 745.7 watts. One metric horsepower (PS, used in much of continental Europe) is 735.5 watts — about 1.4% smaller. A 200 hp car from the US and a 200 PS car from Germany aren't quite the same machine, although the difference is usually within the margin of marketing-rounding.
What's the difference between energy and power?
Energy is the total amount of work done; power is the rate at which work is done. A 100-watt bulb burning for 10 hours uses one kilowatt-hour of energy. Power is always energy divided by time — joules per second, kilowatt-hours per hour, BTU per hour.
How many BTU/h does my air conditioner need?
A common rule of thumb is 20 BTU/h per square foot of cooled space, adjusted for ceiling height, insulation, and sun exposure. So a 300 ft² room typically wants a 6,000 BTU/h unit (about 1.75 kW). Window units are usually rated in BTU/h, while split systems are often rated in kW.
Why do some kettles use 3 kW while others use 1.5 kW?
Mains voltage. UK and European kettles run on 230 V and can comfortably draw 13 A — about 3 kW. North American outlets are 120 V at 15 A — about 1.8 kW — so kettles there boil noticeably slower for the same volume of water. Same kettle design, different power draw because of the supply.