Horsepower-hour is a unit of energy or work equal to the work done by one horsepower in one hour. Horsepower is the unit of power in the English system of measurement. The SI unit of energy is the joule.
One joule = 3.73·10-7horsepower-hour.
The term horsepower was coined by James Watt (1736-1819), the Scottish inventor and mechanical engineer renowned for his improvements of the steam engine. A horse, harnessed to an appropriate machine, can lift 550 pounds at the rate of 1 foot per second.
1 horsepower-hour = 1.97·106 foot-pound
1 horsepower-hour = 6.42·102 kilocalorie (thermal)
1 horsepower-hour = 2.55·10s Btu (thermal)
1 horsepower-hour = 2.68·106 joules
1 horsepower-hour = 0.746 kilowatt-hours
1 horsepower-hour = 2.6813 ergs
1 horsepower-hour = 1.67·1025 electron-volts
1 horsepower-hour = 2.68·1013 dyne-centimeters