Horsepower and Watts

Although he was not first to use the horsepower name, James Watt was the first to apply specific measurement to it. During the 1780s, after making a vastly superior steam engine to the common Newcomen steam engine, Watt was looking for a way to market his invention, advertising the fact that his engine was superior and used about 75% less fuel than a similarly powered Newcomen.

He came up with a new unit of measurement that those in need of his engine understood, horse power, referring to powerful draft horses. He calculated how much power a typical draft horse could generate and figured out a typical draft horse could do about 32,400 foot-pounds of work per minute and maintain that power rate for a full workday. He then rounded up, going with 33,000 foot-pounds per minute for 1 horsepower. By overestimating what a horse could do he made sure that his product would always over deliver what he said when trying to get people to buy it.

Watt’s engine was revolutionary and played a huge role in the Industrial Revolution. His unit of measure of an engine’s power became popular. Today the SI unit of power, the Watt, which was named in homage to James Watt, has widely come to replace horsepower in most applications.