What Is Horsepower and Why is it Important?

A key metric in terms of automotive performance, horsepower measures how fast a vehicle’s engine can produce the force needed to propel it forward and perform various tasks. Horsepower indicates a vehicle’s potential for speed, acceleration, and overall performance. Learn more about how horsepower is calculated, how it applies to different engines, and what it means for your driving experience.

How Does Horsepower Work?

Horsepower measures engine capabilities and how fast a vehicle can deliver force to accelerate, tow a load, or provide traction on slippery surfaces or difficult terrain. The higher a vehicle’s horsepower, the more power it can generate within seconds.

How is Horsepower Calculated?

As a numerical equation, horsepower is calculated by multiplying an engine’s rotations per minute (RPM) by its torque: 

Horsepower = RPM x Torque 

In practical terms, horsepower factors into helping keep drivers safe on the road or more easily operate under challenging conditions. For example, a car with higher horsepower can accelerate faster to merge easily into heavy highway traffic or respond quickly to avoid debris or hazards in the road. Likewise, ample horsepower generates greater stability when navigating rocky, muddy, or steep off-road terrain. 

Subaru has a reputation for exceptional safety, reliability, and performance. Every Subaru vehicle applies thoughtful engineering principles that leverage horsepower to enhance the driving experience in numerous ways. 

  • Emergency maneuvering: Horsepower makes it possible to execute swift emergency maneuvers, such as quick acceleration, steering to avoid obstacles, or sudden braking to respond to unexpected weather, traffic, and road conditions.
  • Tackling steep inclines: Subaru SUVs can scale steep inclines and maintain traction through steep hill descents, even when carrying passengers and cargo. These horsepower capabilities are further enhanced with X-MODE®, a powerful feature that works alongside our Subaru Symmetrical All-Wheel Drive.
  • Confident towing: Subaru vehicles with the highest horsepower engines, including the Ascent and Outback Wilderness, offer the most robust towing capabilities, allowing drivers to haul trailers, campers, or boats with ease.
  • Off-road adventure-ready: Our SUVs, including the Crosstrek and Forester, are built for off-roading. Their increased horsepower helps them easily conquer tough trails and terrain while maintaining stability and control.
  • Thrilling performance: The extra horsepower packed into our Subaru WRX and BRZ performance sports cars help them deliver precision handling, quick acceleration, and impressive responsiveness for an exhilarating experience on winding roads or recreational racetracks.

What is the History of Horsepower?

The idea of horsepower dates back to the late 18th century in Scotland during the Industrial Revolution. Engineer James Watt, who helped develop the steam engine, coined the unit of measurement to express the rate at which a horse could haul coal out of a coal mine and to compare the steam engine’s efficiency when doing the same task. 

Watt approximated calculations as a means to market the power of a steam engine as a replacement for workhorses, capable of moving substantially more pounds-per-foot at the rate of one foot per second compared. As modern machinery evolved, the concept of horsepower became a standard way to evaluate power across a variety of engines, including internal combustion engines, electric motors, and hybrid systems.

How Does Horsepower Work for Different Types of Engines?

Different types of engines generate and deliver horsepower in different ways due to their distinct designs and components. In traditional gasoline-powered combustion engines, horsepower is a product of many factors including engine placement, compression ratio, and fuel delivery. By contrast, electric motors produce horsepower by converting electrical energy into mechanical power. Hybrid engines incorporate both internal combustion and electric motor technologies to produce a combined horsepower measurement.

Horsepower for Gas Powered Cars

Gasoline-powered vehicles generate horsepower as a result of internal combustion within the engine. The size of the engine, along with its cylinder configuration and fuel delivery systems are among the factors that influence how much horsepower an engine can produce. Modifications and enhancements to the engine such as turbochargers can also increase a vehicle’s horsepower output. For combustion engine vehicles, peak horsepower is typically expressed in relation to its engine speed. 

Diesel engines also produce horsepower through combustion and are subject to the same variables. However, they are typically capable of generating more horsepower due to higher air compression and the different type of fuel used. Diesel vehicles tend to be noisier and produce more emissions, making them a less compelling option for drivers who don’t need the extra power.

Horsepower for Electric Vehicles

Electric vehicles (EVs) like the Subaru Solterra produce horsepower by converting electrical energy into mechanical power. Because there is no internal combustion, electric motors can deliver smooth, instantaneous horsepower and torque at impressive levels, remaining efficient without producing any emissions. EVs also offer regenerative braking, where kinetic energy is converted back into electrical energy during braking for ultimate efficiency.

Horsepower for Hybrid Vehicles

Vehicles equipped with hybrid systems combine both an internal combustion engine and an electric motor to generate power. Their horsepower is typically expressed as a combined output. The two power sources are meant to transition seamlessly between one another as needed, with the gasoline engine taking over from the electric motor at higher speeds or when additional power is needed. Many hybrids also incorporate regenerative braking to enhance efficiency.

Explore Our Subaru Vehicles

Whether you’re commuting to work or embarking on weekend off-road adventures, Subaru vehicles are all equipped with ample horsepower to support our Symmetrical All-Wheel Drive system and other safety and performance features. 

Check out our full lineup of vehicles to compare horsepower specs.