Buzz
The term 'horsepower' is familiar to even the most casual car fans as a measure of an engine’s power output. Generally, the higher the horsepower, the more likely a car can outperform a Tesla in a race.
But what exactly does 'horsepower' mean, and how much power does a horse truly have?
According to Science Focus, the idea of horsepower was conceived in the 1700s by engineer James Watt, the namesake of the unit of power. This concept was designed to persuade people accustomed to the labor of horses to switch to Watt’s improved steam engine. By highlighting that a machine could outperform several horses in terms of work capacity, it offered a comparison that enticed people to buy the new technology. After all, if a machine could replace the efforts of multiple horses, why not take advantage of it?
To understand what 'horsepower' actually means, it's important to remember that power refers to the amount of energy transferred (or 'work') during a specific time period. James Watt asserted that a horse could turn a large mill wheel 2.5 times per minute. From this, he determined the total amount of work a horse could perform in an average day, which he called 'horsepower.' Watt concluded that one horsepower was equivalent to 33,000 foot-pounds per minute, or the energy required to lift 33,000 pounds by one foot in one minute.
For those who aren’t mathematically inclined, think of it this way: imagine a horse lifting a 33-pound weight up to 1,000 feet in the air within a minute. That’s what one horsepower looks like.
This is essentially the standard measurement used in modern cars, alongside metric horsepower, which quantifies the power needed to lift a 75-kilogram mass by 1 meter in one second.
So, does one horse have exactly one horsepower? Not exactly. It depends on how much work the horse can do within a given time period. Data from the 1925 Iowa State Fair showed that a horse could reach up to 15 horsepower, though that level is not sustainable. One horsepower refers to the amount of work a horse can perform over an average workday. The higher the horsepower, the faster the rate of work.
For cars, horsepower typically indicates how fast a car can accelerate, although not necessarily from a complete stop. (For that, torque is more relevant.) A car’s horsepower generally refers to its peak output.
Would there ever be a reason to prefer a lower horsepower number? Occasionally. In cars, it could lead to better fuel efficiency. With horses, it might result in a smoother, more comfortable ride.
