Accurately compute pump hydraulic power (kW) and required shaft power (kW) based on flow rate, head, fluid density, and pump efficiency. Ideal for centrifugal pump selection, energy audits, and system design.
The hydraulic power (Phyd) represents the energy transferred to the fluid per unit time, while the shaft power (Pshaft) is the mechanical power input at the pump shaft. The difference is due to pump efficiency (η), which accounts for hydraulic, volumetric, and mechanical losses. Accurate power calculation is essential for motor sizing, energy consumption forecasts, and system optimization.
These equations derive from the Bernoulli principle and are standardised by the Hydraulic Institute (HI) and ISO 9906. Proper pump sizing reduces energy waste — a 5% efficiency increase can save thousands of kWh annually in industrial settings.
A municipal plant operates a centrifugal pump at Q = 320 m³/h, H = 12 m, ρ = 1020 kg/m³, η = 68%. Using our calculator, Phyd = (1020×9.81×0.0889×12)/1000 ≈ 10.67 kW, Pshaft ≈ 15.69 kW. After impeller trimming and η improvement to 74%, the shaft power dropped to 14.42 kW, saving over 11,000 kWh/year. This tool provides immediate insight into energy efficiency measures.
An agricultural project needs Q = 150 m³/h, H = 45 m, water density. With η = 72%, required shaft power = 25.5 kW. The nearest standard motor is 30 kW. The calculator’s motor power estimate includes 10% service factor, ensuring reliable operation under voltage variations.
| Pump type | Typical efficiency range | Notes |
|---|---|---|
| Centrifugal (large, >100 kW) | 75% – 88% | High flow, low viscosity |
| Centrifugal (small, <10 kW) | 50% – 70% | Domestic or light industrial |
| Positive displacement | 65% – 85% | Steady flow regardless of pressure |
| Slurry / Abrasive pumps | 45% – 65% | Wear reduces efficiency |
| Submersible pumps | 55% – 75% | Motor cooling integrated |