What is Horsepower in Cars

When it comes to cars, the first metric we associate when determining whether or not a vehicle is powerful or fast is horsepower. It’s ingrained into our memory from an early age, and it’s such a natural association, it’s often an afterthought. But have you ever stopped to wonder what exactly horsepower is?

In all actuality, horsepower is a completely made-up measurement. The term was created by James Watt, a steam engine pioneer who was looking to find a way to compare the effectiveness of his steam engines compared to that of a horse, which previously did the work of these engines. Watt went on to define one horsepower as being the equivalent of the energy expended by a single horse lifting 33,000 pounds one foot in the air from the surface of the Earth in one minute. 

Sounds pretty elaborate, right? Well, that’s because it sort of is. In light of this, let’s discuss what horsepower is in more detail to help you gain a better knowledge of how it affects your vehicle’s performance.

What is Horsepower?

What horsepower really is can be actually be found within its namesake. As its title implies, it’s a unit of power, so in essence, HP, BHP, PS, CV, and kW all refer to the amount of power produced by an engine. In layman’s terms, horsepower can be deemed how much ‘work’ and engine can do. The general rule of thumb is that the higher the horsepower, the faster a vehicle can go. 

But keep in mind, power also affects acceleration. So not only does power affect a vehicle’s top-end speed, but it also affects acceleration. In most cases, the higher the horsepower, the quicker a car can gain speed.

What is HP Compared to BHP?

Some of you may wonder what BHP is and what the acronym is referring to. Traditionally speaking, BHP stands for ‘brake horsepower’ which has been used as a term for the definitive measurement of an engine’s power. It’s distinctive from traditional horsepower because it takes into account power loss due to friction. BHP is measured through the process of running an engine up to full revving RPM, then letting the vehicle naturally slow down to a dead stop without applying the brake.

As if having to analyze HP and BHP wasn’t enough, both Japanese and European carmakers use a metric measurement of horsepower that only complicates matters further. Many European automakers list the power of the vehicle engines using the German term PS (which means ‘pferdestarke’, the literal German translation of ‘horsepower’. The fight between standard vs metric continues!

Torque vs Horsepower: What’s the Difference?

Though similar in some facets, torque and power are different in many ways. They both are what engines produce when you turn the ignition and press your foot down on the accelerator. This process creates air and fuel that is ignited in the combustion chambers, causing the crankshaft, transmission, and drive axles to engage and, essentially, turn the wheels by spinning the axle. 

This action is all credited to the miracle of energy conversion. Once mankind came up with the ingenious idea to convert fossil fuel into the world’s largest source of energy, this desire to optimize energy conversion became a keen interest to scientists and ambitious entrepreneurs alike.

When differentiating torque and horsepower, keep these key differences in mind.

  • Energy is defined as the capacity for doing work. So in the case of an engine, it performs the work formerly done by horses. Work in this instance is the result of a force that acts over some distance
  • Torque is defined as a rotating force produced by the crankshaft of an engine. So the more torque an engine can produce, the greater its capacity to perform work. The measurement of torque is similar to work but a little bit different. Being that torque is a vector - meaning it acts in a certain direction - it’s quantified by the measurement units of pound-feet and newton-meters.
  • Power can be defined as how rapidly work is being accomplished. Eighteenth-century inventor James Watt - whose last name is synonymous with one of the world’s most recognized metrics of power - bestowed upon us the equivalency we mentioned earlier.

Here’s another way to think about horsepower vs. torque: When you are twisting off the cap on a new pickle jar. When you are trying to open the jar and using all your strength to get the cap off, this is applying torque—regardless of whether the cap comes off or not. On the other hand, horsepower only exists when movement is produced. In our pickle jar example, torque is necessary to loosen the lid. Horsepower would be the action of your hand spinning the lid off quickly.

Why Does Horsepower in Cars Matter?

In general terms, the more horsepower that a car has, the better its acceleration. Horsepower is a strong factor in the overall performance of a vehicle. This is one of the primary reasons that car marketing focuses on horsepower ratings for high-performance models. But keep in mind, there are still additional factors at work. Engines in high-performance vehicles are tuned in a way that the horsepower and torque ratings complement each other fluidly, providing a well-balanced experience for the driver.