Electrical Horsepower to Horsepower (hp (E) to hp)
1 electrical horsepower equals 1.000402479 horsepower (rounded).
How to convert electrical horsepower to horsepower
To convert electrical horsepower to horsepower, multiply the number of electrical horsepower by 1.000402479. The factor is rounded to 10 significant digits. To go the other way, multiply horsepower by 0.9995976831 (rounded).
horsepower = electrical horsepower × 1.000402479
Example: 10 electrical horsepower = 10.00402479 horsepower.
Several different horsepower units exist. This site lists mechanical (745.7 W), metric (735.5 W) and electrical (746 W) horsepower separately.
About these units
Electrical Horsepower (hp (E))
Exactly 746 watts, the horsepower used for electrical power.
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.
1 electrical horsepower = 746 watts (exactly).
Sources: Wikipedia: Horsepower; NIST SP 811, Appendix B.8
Horsepower (hp)
The mechanical horsepower: 550 foot-pounds per second, about 745.7 watts. James Watt coined it to compare steam engines with draft horses.
Horsepower was a sales pitch before it was a unit. Late in the 18th century the Scottish engineer James Watt adopted the term to compare the output of steam engines with the draft horses they replaced. His 1782 experiments found that a brewery horse could produce 32,400 foot-pounds-force per minute, and in 1783 he and Matthew Boulton standardized the figure at 33,000 foot-pounds-force per minute. Customers could then be told how many horses an engine would replace.
That figure works out to 550 foot-pounds-force per second, or about 745.7 watts: the power needed to lift 550 pounds by one foot in one second. Several cousins exist, including metric horsepower and electrical horsepower, defined as exactly 746 W. Car ratings added more confusion. Early British taxable horsepower was a formula based on bore and cylinder count, not measured output, and American ratings before 1972 used SAE gross brake horsepower, measured without accessories. In the European Union, horsepower may be used only as a supplementary unit under Directive 80/181/EEC, in force from 1 January 2010.
1 horsepower = 745.6998716 watts (approximately).
Sources: Wikipedia: Horsepower; Wikipedia: Metric horsepower
Related conversions
- Horsepower to electrical horsepower (reverse)
- Electrical horsepower to watts
- Electrical horsepower to kilowatts
- Watts to horsepower
- Kilowatts to horsepower
- Megawatts to horsepower
- Gigawatts to horsepower
- Metric horsepower to horsepower
- BTU per hour to horsepower
- Milliwatts to horsepower
- Foot-pounds per second to horsepower
- Tons of refrigeration to horsepower
- Kilocalories per hour to horsepower
- Calories per second to horsepower
- Ergs per second to horsepower
See all power units.