Social Good Engineering Magazine: GineersNow Social Innovation GineersNow Engineering Magazine Issue No. 001 | Page 42

ELECTRO-MECHANICAL ENGINEERING
WHY DO WE CALL IT
“HORSEPOWER”
INSTEAD OF ANY
OTHER ANIMAL?
by Raymond Gerard del Valle
Photo Source: Pinterest
I
n this day and age of powerful
machines, there is a big chance
you’ve heard about horsepow-
er. From heavy machinery, to
cars, to air conditioners, to
lawnmowers, the term horse-
power is used to describe an
engine’s power. But, have you ever
wondered why of all animals the
horse was chosen as the benchmark
for power?

The reason was pretty
literal, actually. In the early 1780s,
Scottish engineer James Watt was
looking for a compelling way to
market his new invention – a steam
engine superior to the then classic
Newcomen steam engine. Many of
his prospective customers at that
time used horses to power their
operation, so Watt had to come up
with a new unit of measurement
that he could use to illustrate the
advantage of using his steam en-
gine as opposed to horses. Hence,
horsepower.

The way Watt came up
with the numbers he did is still up
for discussion, but after doing the
experiments that he did, he figured
out that a typical draft horse could
do about 32,400 foot-pounds of
work in 60 seconds, and maintain
that power rate for the entire work
day. That means that, by Watt’s
approximation, a draft horse could
lift 32,400 pounds of material one
foot in one minute. After doing
some rounding up, Watt settled for
33,000 foot-pounds per minute for
one horsepower (hp).

Of course, Watt’s esti-
mates were very generous, as the
horses involved in his experiments
were far from mutants! But that
wasn’t Watt’s original intention
anyway. By overestimating what
a typical horse could do, Watt
made sure that
his product would
always perform
better than the
real horses.
The unit of
measure horse-
power became
popular thanks
to the invaluable
contribution of
Watt’s engine
during the indus-
trial revolution.
Today, however,
the SI unit of
power, the Watt,
which was named
in tribute to James
Watt, is progres-
sively replacing
horsepower in
most applications.
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