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.