Horsepower – History and Trivia


Hello everyone, Winnie Griggs here. Last moth I did a post on the Transcontinental Railroad. While I was doing my research I came across a little footnote on the term horsepower, one of those little trivia nuggets that led me down a rabbit trail. Today I thought I’d share the results of that little research sidetrack.

The concept of horsepower was created in the eighteenth century by a man named James Watt. And believe it or not, it was created as a last ditch marketing gimmick.

In the 1760s, Watt was tasked with repairing a defective steam engine. But Watt was an enterprising inventor and noted some inefficiency problems with the overall design that he thought he could correct.

So instead of completing his assigned task, Watt created a new and improved steam engine that was far and away better than anything on the market at that time. However he had trouble finding any customers willing to give his product a try. The problem was, previous steam engines had failed, in sometimes spectacular ways, making folks unwilling to replace their familiar and reliable horses with yet another version of the engine.

But Watt was not one to give up easily. He decided the answer to his marketing problem was to come up with a unit of measure that would allow him to compare his engine to horses. He poured a lot of time and thought into how he would do this. Watt eventually came up with a unit of measure that was defined as the power exerted by a single horse to move 33,000 pounds of material one foot in one minute. He dubbed this unit of measure the horsepower.


His calculations went something like this: He had observed ponies at a coal mine and  figured out that on average the animals were able to move 220 pounds of product over a mineshaft 100 feet long in one minute. By his calculation, that was equivalent to 22,000 pounds over one foot in one minute. Then he made one additional tweak to his calculation – he figured a horse could do 50 percent more work than a pony, thus his new horsepower measurement would equal 33,000 foot-pounds of force per minute.

As you can see, the manner in which he computed his horsepower measurement was not truly scientific, nor was it entirely accurate, but the important thing to Watt was that it gave him a method to convey the power of his engine in a manner people could visualize. Armed with this new way of measuring his engine’s power, he claimed his machine had the power of ten horses, in other words ten horsepower. It worked – people were receptive to this new way of looking at his engine and so were willing to reconsider the value of his machine.  This tactic proved so successful that his competitors began using horsepower in their advertisements and sales pitches too.  And this unscientific measurement that was developed as a marketing tactic is still in use today, more than 240 years later.

A couple of additional bits of trivia

  • Because of The Watt Engine’s rapid incorporation into many industries, many consider the Watt engine to be one of the defining developments of the Industrial Revolution.
  • James Watt was later recognized for his contributions to science and industry, the unit of power in the International System of Units, the watt, was named for him.
  • An actual horse’s peak power has been measured at  just under 15hp. However, for prolonged periods of time, the average horse can’t deliver even one horsepower.

There you have it, a short accounting of what I discovered about the origins of the term horsepower. So what do you think, did any of the information in this post surprise you?  Leave a comment to be entered in a drawing for a copy of any of my backlist books.