The meaning of "Horsepower"

The term "Horsepower" was coined by James Watt, the Scottish engineer and inventor of the light bulb. In the early 18th century, steam engines revolutionized mining and manufacturing processes. Watt improved the efficiency of these machines by moving the condensation process outside the cylinder and incorporating centrifugal governors for maintaining a constant speed under varying loads.

He obtained a patent for his invention in 1769, which proved to be groundbreaking. Steam engines soon spread to various industries.

To illustrate the power of steam engines, Watt chose the work capacity of a horse pulling a load. The horsepower of his improved machines served as a marketing tool and justified their price by replacing the work of multiple horses. However, it is uncertain which horses he referred to—whether they were pit ponies used in mining, horses driving winding gears, or those lifting heavy coal sacks using pulleys.

Nevertheless, he arrived at a power of 33,000 foot-pounds per minute. This unit, abbreviated as ft·lb, ft·lbf, lb·ft, or lbf·ft, refers to the Anglo-American foot as a length measurement (30.48 cm) and an Anglo-American pound equal to 0.453592370 kg.

Converted to seconds, it equals 550 ft × lbf/s, which is equivalent to 76.04 kp·m/s (kilopond = weight force of 1 kg). When the metric system was adopted in continental Europe, the Anglo-American horsepower was adjusted to a value of 75 kp·m/s.

Thus, the European horsepower slightly differs from the horsepower commonly used in the Anglo-American region. In the DIN 66036 standard, 1 horsepower (hp) is defined as the power required to move a body with a mass of 75 kg against the standard acceleration due to gravity of 9.80665 m/s² at a speed of 1 m/s.

Machine vs. Horse: The similarities

Early on, horses (and cattle) were used as tools in agriculture and transportation, providing far greater work capacity than humans. They significantly increased agricultural yields, enabled faster travel over long distances, and opened up new trade opportunities. Horses also powered wheels to lift loads and served as beasts of burden and draft animals—essentially, they were the machines of our ancestors. Humans selectively bred horses to enhance their performance for specific purposes, leading to the development of specialized breeds.

With the advent of steam engines, horsepower became a benchmark for measuring their power.

These machines gradually replaced the labor of horses. Horsepower allowed for the illustration and comparison of machine power. Consequently, it made sense to use the unit for measuring the strength of emerging gasoline and diesel engines that replaced horses as the primary means of transport.

Horsepower to kilowatts (kW): Conversion process

As early as 1899, the International Electrical Congress recommended using watts and kilowatts (kW) instead of horsepower for power measurement. This recommendation quickly gained traction for electric motors (the power of electric cars is exclusively described in kW), but not for internal combustion engines. In the 1970s, European countries adopted the International System of Units (SI units), which includes kW.

However, internal combustion engines are still marketed with their horsepower rating, possibly because higher horsepower figures sound more powerful.

The usage of horsepower for internal combustion engines has likely become entrenched due to its ease of understanding and familiarity, unlikekW, which may be less intuitive. When buying a used vehicle, you will often come across the horsepower rating.

Manufacturers, importers, and dealers also predominantly use horsepower. However, in technical literature, horsepower has become almost obsolete. In vocational training, calculations related to motor power are done using kW, while horsepower plays a role in vehicle performance and usage.

To convert horsepower (hp) to the SI unit of kilowatts (kW), the following formulas apply:

• 1 horsepower = 0.735 kW

• The reverse is true for the conversion from kW to hp:

• 1 kW = 1.36 horsepower

• Alternatively, for a rough estimate:

• 1 horsepower ≈ 3/4 kW

• 1 kW ≈ 4/3 horsepower

How much horsepower does an average car have?

In theory, 60 to 70 horsepower would be sufficient for a vehicle's basic mobility. Imagine a team of 60 horses and what they could accomplish. However, the more horsepower a car has, the faster it can reach its top speed.

The acceleration of an engine also depends on its torque: the higher the torque, the faster the vehicle can reach 100 km/h. Torque is measured in Newton-meters (Nm) or in the Anglo-American system, pound-feet (lb/ft). Combustion engines require high engine speeds (revolutions per minute, rpm) to achieve maximum acceleration.

In contrast, electric vehicles provide instant acceleration due to their high torque.

The cars manufactured in 2020 had an average of 165 horsepower (hp), which is significantly more than what is required for basic transportation purposes. Vehicles with high horsepower are not only more expensive to purchase and maintain but also experience greater depreciation in the early years compared to lower horsepower models.

The increase in average horsepower is mainly attributed to the higher proportion of electric and hybrid vehicles, which have an average of 169 horsepower.

Your CARIFY Car

Horsepower (hp) is not just about speed but primarily about power. How much horsepower does each vehicle need? Let's take a closer look at our CARIFY offerings. With us, you can filter your desired vehicle based on horsepower.

• 0-100 horsepower: In this category, you will find predominantly small cars powered by gasoline, such as the Opel Corsa, Fiat 500, or VW Polo. Additionally, small hybrid models like the Suzuki Swift or Honda Jazz, as well as electric cars like the Smart Fortwo and VW Up, fall into this horsepower range. These small and lightweight vehicles are ideal for city driving and have low fuel consumption. For short-distance transportation, the VW Caddy Kombi with a diesel engine is suitable.

• 100-200 horsepower: Most of our vehicles at CARIFY fall into this horsepower category. You will find compact small cars as well as sedans, wagons, SUVs, and vans of all fuel types. They are all suitable for long-distance driving and can handle various loads.

• 201-300 horsepower: This category includes large SUVs, heavy sedans, and wagons, many of which have hybrid or electric drivetrains. Electric minivans and commercial vehicles are also considered high-horsepower vehicles, allowing you to reach high speeds and carry heavy loads on long-distance journeys.

• 300-2,000 horsepower: Spacious SUVs (gasoline, hybrids, and electric vehicles) are predominantly found in this category, as well as some sedans. If you prefer a particularly fast driving experience, you'll find sporty convertibles and coupés from renowned brands like Porsche, or Jaguar with high horsepower.

Conclusion

Horsepower will continue to be an easily understandable unit of measurement for some time, even as its usage decreases. This is due to the growing number of electric vehicles, which are measured in kilowatts (kW) for their power output.

At CARIFY, you can find car subscriptions with various levels of horsepower.