Pump Efficiency Calculator

There is no universal efficiency threshold that is “good” for every pump. Expected efficiency depends on pump type, size, specific speed, flow, head, fluid, speed, and operating point. Compare the calculated value with the manufacturer's pump curve and with expected performance for the specific equipment.

Calculate hydraulic power from flow, head, density, and gravity, then divide hydraulic power by the pump shaft input power. Multiply the decimal ratio by 100 to express pump efficiency as a percentage.

The pump-level formula is η = P_hyd/P_shaft. For an incompressible liquid using head, P_hyd = ρgQH, so η = ρgQH/P_shaft. The denominator must represent shaft power, not uncorrected motor electrical input.

Hydraulic power is the useful rate of energy transfer from the pump to the fluid. For a liquid using head, it is ρgQH. If pressure rise is known directly, the incompressible form is ΔP × Q.

Use P_hyd = ρgQH with SI units, or P_hyd = ΔP × Q when the measured pressure rise is the appropriate hydraulic pressure increase across the pump. The two forms are related through ΔP = ρgH.

Motor efficiency compares mechanical shaft output with electrical input. Pump efficiency compares hydraulic output with shaft input. They are separate conversion stages, so multiplying them gives an idealized overall wire-to-water efficiency when other drivetrain losses are represented correctly.

No. Pump efficiency covers the pump's conversion of shaft power into hydraulic power. Overall system efficiency can also include motor, drive, controls, piping, valves, operating point, and system-level losses.

The Best Efficiency Point is the point or region on a pump performance curve where pump efficiency is highest for the stated speed and configuration. It is identified from the manufacturer's curve rather than assumed to equal rated flow.

Changing flow moves the operating point along the pump curve. Internal recirculation, hydraulic incidence, friction, leakage, and other loss mechanisms change with operating point, so pump efficiency is not constant across the full flow range.

No for a physically consistent pump-efficiency calculation. If the result exceeds 100%, hydraulic output is greater than the corresponding shaft input, indicating an input, unit, measurement, or reference error that should be checked.

Possible causes include operation away from BEP, wear, damaged or trimmed impellers, excessive clearances, recirculation, unsuitable pump selection, changed fluid properties, lower speed or wrong speed assumptions, and measurement errors.

Head is directly proportional to hydraulic power for fixed flow and density. Therefore, an error in measured or calculated head directly changes the computed hydraulic power and the resulting pump efficiency.

Density affects hydraulic power when head is used because P_hyd = ρgQH. If pressure rise is used directly with P_hyd = ΔP Q, density is not required for the power calculation, although it is needed to convert pressure rise to equivalent head.

Yes, if the relevant pressure rise across the pump is known for an incompressible fluid. Hydraulic power can be calculated as ΔP × Q, then divided by pump shaft input power to obtain efficiency.

Yes. With flow rate, head, fluid density, and pump shaft input power, calculate hydraulic power from ρgQH and divide by shaft input power.

If hydraulic power and pump efficiency are known, required shaft input is P_shaft = P_hyd/η_pump. If the desired input is motor electrical power, motor efficiency must also be considered.

First calculate the hydraulic duty from flow, head, and density. Divide that hydraulic power by the expected pump efficiency to obtain the required shaft input power. This is a duty calculation, not final motor sizing.

Shaft power is the mechanical power delivered to the pump shaft. It is the correct pump-input denominator for calculating pump hydraulic efficiency. It differs from the motor's upstream electrical input because the motor itself has losses.

Motor input power is electrical power supplied to the motor. Shaft power is the mechanical power that leaves the motor and reaches the pump shaft. Motor efficiency relates the two quantities.

Yes for basic centrifugal-pump duty and efficiency estimates when flow, head or pressure rise, density, and power information are appropriate. Final performance should still be checked against the manufacturer's curve at the actual speed and impeller configuration.

Yes. The calculator includes an editable approximate water-density reference near 20°C. Use actual density and operating data if temperature, pressure, dissolved solids, or fluid composition differ materially.

It can provide a preliminary performance calculation for many liquid pumping applications. Industrial audits and equipment decisions should also use calibrated measurements, actual pump curves, motor data, system operating conditions, and appropriate engineering procedures.

Wire-to-water efficiency is hydraulic power delivered to the fluid divided by electrical power entering the motor or drive system. It includes more of the energy-conversion chain than pump efficiency alone.

Wear can increase internal leakage, alter clearances, roughen flow passages, damage impeller surfaces, or change hydraulic performance. These effects can reduce the hydraulic output obtained for the same shaft input.

Impeller trimming changes the pump curve and can also change efficiency. The effect depends on pump design and trim amount, so use the manufacturer's trimmed-impeller performance data rather than assuming one fixed efficiency penalty.

Changing speed moves the operating point and changes flow, head, and power. Efficiency can also shift because the pump operates at a different part of its performance map. Manufacturer or tested data is preferable for precise evaluation.

Away from BEP, internal hydraulic losses, recirculation, incidence, flow separation, and other effects can increase. The exact efficiency decline depends on the pump and operating point, so the manufacturer curve should be used for comparison.

Yes, if the same hydraulic duty can be delivered with lower shaft and electrical input. Actual savings depend on operating hours, motor and drive efficiencies, system control, load variation, electricity tariff, and whether the duty itself changes.

Determine actual flow, head, speed, fluid, and shaft or electrical power, calculate field efficiency, then compare it with the manufacturer's efficiency at the corresponding operating point and configuration. Ensure both values use compatible power definitions.

Typically you need flow rate, differential head or pressure, fluid density, and pump shaft power. If only motor electrical input is measured, motor efficiency or more detailed electrical/drive data is needed to separate pump efficiency from overall efficiency.

Yes. Higher viscosity can alter hydraulic losses, flow, head, required power, and the pump curve. The simple efficiency formula still applies to measured quantities, but predicted performance may require manufacturer viscosity corrections or a more detailed pump model.

Yes. Pumps of different sizes and hydraulic designs can have different achievable efficiencies even at similar duty points. That is why universal “good efficiency” thresholds are not appropriate for every pump.

Review the units and measurements. Check flow conversion, head or pressure references, density, input-power basis, motor-efficiency assumptions, instrument accuracy, and whether all measurements represent the same operating condition.

The appropriate interval depends on equipment criticality, energy cost, maintenance strategy, service severity, and whether operating conditions change. Trending flow, head, power, vibration, and performance can help identify degradation before a formal efficiency test is repeated.

No. It can quantify a simplified efficiency estimate and potential energy differences. Replacement decisions should also consider reliability, maintenance, lifecycle cost, system requirements, control strategy, pump curve, operating hours, and the cost of modifying the system.