How Much Horsepower Does A Horse Have?

It's almost impossible to see a car advertisement or read a SlashGear automotive review without hearing about how many horsepower an engine has. This measurement has been around since the 18th century, when inventor James Watt adapted the term from its existing use to measure the power of waterwheels. At the time, the term was sometimes used to measure the power generated by waterwheels, which were driven by moving water from a stream or waterfall. Watt popularized the term in an effort to quantify the output of his innovative steam engine design. With the help of assistant John Desaguliers, Watt estimated that a horse could lift 33,000 pounds one foot in one minute, and made that his standard — although he might have been better off calling his new unit of measurement "personpower." 

According to the University of Calgary's Energy Education web page, a human can produce a little over one horsepower, and a horse can generate up to 15 horsepower.

Watt wanted the measurement to reflect how much work a horse could average over a full day, further defining the unit as "the amount of work required from a horse to pull 150 pounds out of a hole that was 220 feet deep." At the time, people were regularly asking Watt how many horses his steam engine could replace, so he devised horsepower as a way of answering that question. Many years later, another standardized measure of energy output was named for Watt. One Watt is equal to one joule of work done in one second. A joule is a different measure of energy output equal to the force required to move one nNwton a distance of one meter, and equals about 0.74 foot-pounds. One horsepower equals 746 Watts; the Watt became an international standard in 1960.

The other common measurement of engine power used in the auto industry is torque. While torque measures the amount of energy an engine produces, horsepower quantifies how it is applied over time. So while the Koenigsegg Jesko Absolut pictured above has a twin-turbo V8 engine rated at 1,600 horsepower, that is more akin to the capability of several dozen horses than it is to a team of 1,600.