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Replacing an engine with an electric motor? Horsepower is horsepower – or is it?

Publication date: 
June 2017
Chuck Yung, EASA Senior Technical Support Specialist
Type of media: 

When a customer calls and wants to replace his diesel or gasoline engine with an electric motor to drive a piece of machinery, it’s easy to assume that “horsepower is horsepower.” Not so fast! It turns out that there are many different ways to measure power. The term horsepower was adopted by James Watt in the late 1700s to compare the output of steam engines to draft horses. Aside from North America, most of the world uses the International System of Units (SI) unit watt to describe power output. Since the 1700s, we have mechanical hp, kW, metric hp, electric hp, hydraulic hp, drawbar hp, brake hp, shaft hp and even variants of taxable hp. Leave it to governments to want a piece of the action.

The purpose of this article is to increase awareness about the many factors which must be considered when making such a seemingly simple substitution. 

AC motors
DC motors