How do you calculate the power of a centrifugal pump?

The input power, that is, the power required to operate the pump should be stated in Hp (horsepower) on the pump’s nameplate. It can also be calculated by the 3-phase power equation:
P(in Hp) = VI(1.7c) = Rated Voltage x Rated Current x 1.73/ %Efficiency
If this is a consumer grade pump that operates on 120Vac, then the equation becomes P = VI, simply multiply the operating voltage, 120 x current (which is the number followed by the letter “A”.
The output power, which really is not technically power, but rated in Gpm (gallons per minute), or capacity should also be on the nameplate. If you have the make, model, and (not necessarily needed) the serial number (also on the nameplate) you could call the manufacturer’s customer service dept. As an application engineer, I have contacted countless manufacturers, and service dept’s for assistance. It is now big deal to them, they will be happy to answer your questions.

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