EVs and Horsepower? How to Convert kW to HP

When most people think about automotive performance, horsepower figures come to mind. We have used the HP figures for generations to compare the engine power of different vehicles. First adopted in the 18th century to measure the output of steam engines, horsepower became one of the headline metrics for automotive marketing.

Many car manufacturers are using the transition to EVs as a clean slate, and you will often see electric motor power stated in kilowatts (kW) instead of horsepower. Both metrics measure power, or the rate at which work is being done. But how do kW and HP compare? How do we convert kW to HP to get a relative idea of the performance of an electric vehicle?

Horsepower was Derived from Watts

Horsepower is actually based on watts. Going back to our 18th-century story; watts of power was kind of difficult to visualize, and at the time horses were commonly used for transport and field work. So it was determined that an average horse could sustain a power output of 745.7 watts (0.745 kW), and the horsepower was born as a measurement unit of engine power.

That means you can calculate the number of kW of a gasoline engine by multiplying the hp bt 0.745, and conversely, you can multiply the motor kW by 1.34 to get the horsepower figure of a motor.

Since EV battery capacity is measured in kWh (kilowatt hours), it made sense to the industry to provide motor power in kilowatts (kW). This also allows other interesting calculations without having to convert units. For example; an EV motor that is generating 25 kW driving on the highway will deplete a 75 kWh battery in approximately 3 hours.

Examples of Common EVs and their Power Output in kW and HP