What is hydraulic power?

Hydraulic power (also called water power) is the useful mechanical power transferred to the fluid: P = ρ·g·Q·H, where ρ is density (kg/m³), g = 9.81 m/s², Q is volumetric flow (m³/s) and H is the total dynamic head (m). It does not include pump or motor losses.

How is shaft (brake) power calculated?

Shaft power equals hydraulic power divided by the pump's hydraulic efficiency: P_shaft = P_hyd / η_pump. This is the mechanical power the motor must deliver to the pump shaft to achieve the desired flow and head.

What is a typical pump efficiency?

Centrifugal pumps typically operate at 55–85% efficiency near their best efficiency point (BEP). Small pumps and pumps far off their BEP can drop below 40%. Always size pumps to operate within ±10% of BEP.

Why does the calculator separate pump and motor efficiency?

Hydraulic, shaft and electrical input power are three different points in the energy chain. Separating them lets you isolate where losses occur — useful for retrofit decisions like upgrading to a premium-efficiency (IE3/IE4) motor or installing a VFD.