Electrical Horsepower (hp (E))

US & ImperialCurrent unit

Exactly 746 watts, the horsepower used for electrical power.

1 electrical horsepower = 746 watts (exactly).

About the electrical horsepower

Electrical horsepower exists because electric motors needed a rating that fits neatly with watts. Mechanical horsepower goes back to James Watt, who compared steam engines with brewery horses and, with Matthew Boulton, settled on 33,000 foot-pounds per minute in 1783. That works out to about 745.7 watts. The electrical version rounds the figure to exactly 746 watts, so that motor ratings convert cleanly to kilowatts.

The difference from the mechanical unit is under 0.05 percent, far smaller than the gap to the metric horsepower of about 735.5 watts, which is roughly 98.6 percent of the imperial one. A motor nameplate normally states shaft output, not the electrical power drawn from the supply, and US nameplates use horsepower where most other countries use watts or kilowatts. NIST lists the electric horsepower as exactly 746 watts.

Sources: Wikipedia: Horsepower; NIST SP 811, Appendix B.8

Electrical Horsepower conversion chart

1 electrical horsepower expressed in every other power unit:

More US & Imperial units

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