A horsepower is a unit of measurement, used to indicate an amount of power or work/time. One horsepower is equivalent to 746 watts, or 2,545 BTUs (British Thermal Units) per hour. This measurement has been attributed to James Watt, one of the inventors of the steam engine; Watt worked in a coal mine and created the measurement to describe the amount of work the 'average' work horse could do in an hour.

Gorgonzola notes that one horsepower is also equivalent to 550 ft-lb/sec2.