Power Converter
Convert between Power units. Choose from 13 different units including Watts, Kilowatts, Megawatts.
Popular Conversions
All Units
| From | Watts (W) |
|---|---|
| Watts (W) | 1 |
| Kilowatts (kW) | 1000 |
| Megawatts (MW) | 1000000 |
| Gigawatts (GW) | 1000000000 |
| Milliwatts (mW) | 0.001 |
| Horsepower (mech.) (hp) | 745.7 |
| Horsepower (elec.) (hp(E)) | 746 |
| Horsepower (metric) (PS) | 735.499 |
| BTU per Hour (BTU/h) | 0.29307107 |
| BTU per Minute (BTU/min) | 17.584264 |
| Foot-Pounds per Second (ft·lbf/s) | 1.35582 |
| Calories per Second (cal/s) | 4.184 |
| Tons of Refrigeration (TR) | 3516.853 |
Energy with a stopwatch attached
Power is the rate at which energy is delivered or consumed: one watt equals one joule per second. That single definition has to cover everything from the microwatts in a hearing aid to the gigawatts leaving a nuclear plant, so engineers and marketers have layered on a small zoo of alternative units, most of them traceable to a specific industry.
James Watt's marketing problem
Around 1782, James Watt needed a way to sell steam engines to mine owners who thought in horses. He measured the rate at which a draft horse could lift coal from a pit and rounded the figure into the unit now called mechanical horsepower, equal to about 745.7 W. The number was generous to the horse but excellent for sales, and the unit outlived its original purpose by more than two centuries.
Continental Europe later adopted a slightly different definition, the metric horsepower (PS, Pferdestärke), equal to 735.5 W. American motor manufacturers settled on a third value, electrical horsepower, defined as exactly 746 W.
Where power units show up
Each industry has its dialect:
- Automotive: kW, metric PS in Europe, mechanical hp in the US and UK.
- HVAC: BTU per hour for heating and cooling output, and tons of refrigeration for chillers, where 1 TR equals 3,517 W.
- Electrical engineering: watts and kilowatts for real power, with kVA reserved for apparent power.
- Lab thermodynamics: calories per second still appears in older calorimetry papers.
Mistakes worth watching for
The horsepower trap is the most common: a 100 hp figure on a European brochure (PS) is not the same as 100 hp in an American catalogue (mechanical hp), and the difference of about 1.4 percent compounds in performance comparisons. The ton of refrigeration sounds like a mass but is a power; it derives from the rate at which one short ton of ice melts over 24 hours, absorbing roughly 3.517 kW. On motor nameplates, kW and kVA are not interchangeable: kVA is apparent power and only equals kW when the power factor is one, which real motors rarely achieve.