Horsepower is a unit of power, while kilowatt-hours is a unit of energy. To go from horsepower to kilowatt-hours, you need to know how long the power is being exerted. For example, a 100-horsepower engine running for five minutes would use significantly fewer kilowatt-hours than the same engine running for five hours.

Multiply the number of horsepower by the time the power is exerted. For example, if you have a 20-horsepower motor running for three hours, you would multiply 20 by 3 to get 60 horsepower-hours.

Multiply the number of horsepower-hours by 0.7457 kilowatts per horsepower-hour to convert to kilowatt-hours. In this example, you would multiply 60 by 0.7457 to get 44.742 kilowatt-hours.

Check your answer using an online calculator. Enter the horsepower and the appropriate amount of time, and the number of kilowatt-hours will be displayed.

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About the Author

Mark Kennan is a writer based in the Kansas City area, specializing in personal finance and business topics. He has been writing since 2009 and has been published by "Quicken," "TurboTax," and "The Motley Fool."

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