Power conversion is how you compare motors, heaters, and generators when one label shows watts and another shows horsepower or kilowatts. Power is energy per time — the rate at which work is done or electricity is delivered — so the same machine can be described in W, kW, or hp without changing its output. This guide is the category overview: formulas, a reference table (including hp↔kW), and tool links. For the full automotive and appliance walkthrough of horsepower and kilowatts, use the dedicated horsepower to kilowatts article.
Convert power now: Open the free Power Converter — watts, kilowatts, horsepower, and related units. No sign-up required.
What power conversion covers
Power measures how fast energy is used or produced. One watt equals one joule per second. Kilowatts suit household and industrial loads; horsepower remains common on engines and some motor nameplates. Converting power keeps those nameplates comparable when you size breakers, compare generators, or read mixed datasheets.
Energy (kWh, joules) is a total over time. If you need totals rather than rates, use the energy conversion guide instead.
Plain-language power formulas
- Watts ↔ kilowatts: divide W by 1,000 for kW. Multiply kW by 1,000 for W.
- Mechanical horsepower ↔ watts: 1 hp (mechanical) ≈ 745.7 W ≈ 0.7457 kW.
- Metric horsepower ↔ watts: 1 metric hp ≈ 735.5 W — slightly less than mechanical hp.
- Kilowatts ↔ mechanical horsepower: multiply kW by ≈ 1.341 for hp (or divide hp by 1.341 for kW).
Always match the horsepower convention on the nameplate (mechanical vs metric) before you trust a one-line factor.
Horsepower ↔ kilowatts reference table
Quick lookup for mechanical horsepower. For worked vehicle and appliance examples, see horsepower to kilowatts.
| hp (mech.) | kW (approx.) | W (approx.) |
|---|---|---|
| 0.5 | 0.373 | 373 |
| 1 | 0.746 | 746 |
| 5 | 3.728 | 3,728 |
| 10 | 7.457 | 7,457 |
| 50 | 37.285 | 37,285 |
| 100 | 74.570 | 74,570 |
Watts to kilowatts (everyday loads)
| W | kW |
|---|---|
| 100 | 0.10 |
| 500 | 0.50 |
| 1,500 | 1.50 |
| 3,000 | 3.00 |
| 7,500 | 7.50 |
Worked examples
Example 1 — space heater nameplate
A heater is rated 1,500 W. In kilowatts: 1,500 ÷ 1,000 = 1.5 kW. That is the rate; overnight energy use still depends on hours run (kW × hours = kWh).
Example 2 — small motor in horsepower
A pump motor is labeled 2 hp (mechanical). In kilowatts: 2 × 0.7457 ≈ 1.49 kW. Confirm whether the label means mechanical or metric hp before ordering a replacement.
Example 3 — generator listing in kW
A portable generator advertises 3.5 kW continuous. In mechanical horsepower: 3.5 × 1.341 ≈ 4.69 hp. Use continuous rating for load planning, not peak surge.
Common power conversion mistakes
- Confusing kW with kWh. Kilowatts are power; kilowatt-hours are energy.
- Ignoring mechanical vs metric horsepower. The factors differ (~745.7 W vs ~735.5 W).
- Comparing peak and continuous ratings. Convert the same rating type on both machines.
Power converter tools
Use the multi-unit Power Converter for watts, kilowatts, horsepower, and related pairs:
Related reading
- Horsepower to kilowatts — deep dive for hp↔kW use cases and examples
- Engineering unit conversion reference — bridges force, power, and pressure
- Unit conversion chart & calculator guide — full category map