Convert Watts to Electrical Horsepower
Convert Watts (W) to Electrical Horsepower (hp(E)) instantly and accurately.
Conversion Formula
hp(E) = W × 0.001340482574
About Watts
The watt (W) is the SI unit of power - 1 J/s - named after James Watt (1736-1819). Familiar power levels: smartphone charging 5-65 W; laptop 15-100 W; microwave 700-1,200 W; electric kettle 2,000-3,000 W; human resting metabolism ~80 W; peak sprint ~2,000 W. The now-obsolete 100 W incandescent bulb is replaced by a 10-15 W LED producing the same light. In AC circuits, reactive power uses the var and apparent power the VA, both derived from watts. 1 W = 1 J/s = 1 kg·m²/s³.
About Electrical Horsepower
The electrical horsepower (hp(E)) is defined as exactly 746 W - the US NEMA rounding used on electric motor nameplates. It differs from mechanical hp (745.7 W) by only 0.04%. Every NEMA-rated motor in the US carries a horsepower nameplate: a '5 hp motor' delivers 5 × 746 = 3,730 W. NEC motor branch-circuit sizing tables, overload relay selection, and starter ratings are all based on hp(E). Despite global kW adoption, US industrial motor infrastructure remains standardised in electrical horsepower. 1 hp(E) = 746 W.
Quick Reference Table
| Watts (W) | Electrical Horsepower (hp(E)) |
|---|---|
| 1 W | 0.00134048 hp(E) |
| 2 W | 0.00268097 hp(E) |
| 5 W | 0.00670241 hp(E) |
| 10 W | 0.0134048 hp(E) |
| 25 W | 0.0335121 hp(E) |
| 50 W | 0.0670241 hp(E) |
| 100 W | 0.134048 hp(E) |