What is Horsepower?

By CarMoney June 30, 2021
What is Horsepower?

You’ve probably heard horsepower referred to in relation to your car before. But what is the difference between horsepower, brake-horsepower, kilowatts, pferdestarke, and chevaux vapeur? Our expert CarMoney guide explains all! 

In essence, they all refer to the amount of power a car’s engine produces. As a rule of thumb, the higher the hp is, the higher the top speed. Power also affects the car’s acceleration, so once again, the higher the hp, the quicker a car will gain speed. 

European and Japanese car manufacturers use a metric measurement of hp. Most quote their engines’ power using the German term PS (pferdestarke, the literal translation of ‘horsepower’), though some use the French term CV (chevaux vapeur).  

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Horsepower vs Brake Horsepower

Brake Horsepower (BHP):

You have likely heard the phrase brake horsepower (bhp) thrown around when talking about cars, and it has been used as the definitive measurement of engine power for a while. It’s different from hp because it takes into account power loss due to friction. It’s measured by running an engine up to full revs, then letting it naturally slow down to a dead stop. 

Horsepower (HP):

One hp is slightly more than one brake-horsepower. That’s why you’ll see, say, an Audi RS 3 listed as pumping out 400PS, but a British car magazine will quote a power figure of 394bhp.

Why the different measurements? No real reason, just people are set in their ways!

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What about Kilowatts?

Kilowatts have had an interesting history as they used to be the preferred measurement of power. However, many manufacturers now prefer to use horsepower due to the numbers being higher, and therefore sounding more impressive!

But kilowatts are making a comeback, mostly thanks to the rise in popularity of electric vehicles (EVs), as it’s the usual measurement for the power of a battery.

The Importance of Torque

In simple terms, torque is a different measurement of the work an engine can do, taken from a different part of the engine. It’s possible for an engine to have high power but low torque, or vice versa. Separate from hp, torque explains how strong the pull of an engine is. The best engines will have high amounts of power and torque.

Why is it called Horsepower?

A common question is often ‘is 1HP equal to a horse?’ and the answer is not quite. Horsepower is a term that was originally coined by James Watt, the Scottish engineer, in order to compare the power of a steam engine to that of a horse. It was then later adapted to engines of other kinds too, such as those now found in cars.

How do I work out the HP of my car?

You can often find the details for hp for various cars online, or, if you fancy a wee maths challenge, you can look to calculate hp with the following formula: 

Horsepower = Torque x RPM/5,252

How much Horsepower does a Human have?

It will of course depend on the health and fitness of the human in question, but a healthy human can produce around 1.2HP for a brief amount of time, and 0.1HP for a consistent period. Elite trained athletes may be able to manage up to 2.5HP briefly! 

Find a car on finance and review the horsepower of each before you decide on which vehicle is right for you. 

 

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