How to calculate pumping power

Written by james wiley
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How to calculate pumping power
(pump image by Aleksander Nordaas from

Pump power is expressed in the unit of watts--more specifically, kilowatts. The actual calculations of pump power are simple once all the variables involved are identified. Certain tests or calculations may need to be performed in order to determine certain variables such as flow capacity and the density of the fluid. The measurement for the differential head should be indicated in the pump manual and the gravity measurement is always constant.

Skill level:
Moderately Easy

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  1. 1

    Identify the flow capacity (in m3/hour), the density of the fluid (in kg/m3), and the measurement for the differential head (in m). The measurement of gravity is constant (9.81m/s2). These numbers are vital to determining the pump power (Ph, measured in kW).

  2. 2

    Multiply the flow capacity by the density of the fluid, the constant for gravity and the measurement for the differential head.

  3. 3

    Divide the number obtained in Step 2--where you multiplied gravity and all the variables--by 3.6 million. The resulting number is the pump power for your specific pump, measured in kilowatts.

  4. 4

    Divide the pump power by the pump efficiency if you want to determine the shaft power of the pump.

Tips and warnings

  • In the kg/m3 measurement, the "3" refers to cubed.

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