IES
Mechanical Engineering2D

Pump Efficiency Calculator

Calculate pump hydraulic efficiency, wire-to-water efficiency, and energy losses.

Inputs
Enter your values below
Result
Pump Efficiency
—
Enter values and click Calculate
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Formula
density × flow × 9.81 × head ÷ power_input × 100
Result unit: %

Efficiency η = Hydraulic Power / Shaft Power × 100%. Hydraulic = ρQgh (W); power_input converted to W by engine. Result in percent.

Introduction

Calculate pump efficiency from hydraulic output power and input shaft power. Typical centrifugal pump best efficiency point (BEP) is 70-85%. Wire-to-water efficiency also accounts for motor efficiency.

How This Calculator Works

Efficiency η = Hydraulic Power / Shaft Power × 100%. Hydraulic = ρQgh (W); power_input converted to W by engine. Result in percent.

Step-by-step process:

  1. Enter your input values in the calculator above
  2. The engine converts all inputs to SI base units (meters, kg, Pa)
  3. The formula is evaluated: density * flow * 9.81 * head / power_input * 100
  4. Result is formatted with the appropriate unit and precision

Calculation Example

100 m³/h × 50m head, 22 kW shaft input: 62.1% efficiency. Hydraulic power = 13.65 kW.

Inputs: flow=100, head=50, power_input=22, density=1000
Result: 62.1 %

Unit Conversion for Pump Efficiency

**Power units**

- 1 kW = 1.341 hp

- 1 hp = 0.7457 kW

- 1 kW = 1000 W

**Flow units**

- 1 m³/h = 0.2778 L/s = 4.403 US gpm

**Pressure units**

- 1 bar = 100 kPa = 14.5038 psi

Hydraulic power P = ρgQH/η requires consistent SI units: density in kg/m³, flow in m³/s, head in m, giving power in W. Convert to kW or hp afterwards.

Engineering Applications

  • •Pump performance evaluation
  • •Energy audits
  • •Pump replacement decisions
  • •Operating cost estimation

Frequently Asked Questions

What is good pump efficiency?

Centrifugal pumps: 70-85% at BEP for medium/large pumps; 50-70% for small pumps. Positive displacement: 65-80%.

What is wire-to-water efficiency?

It includes motor efficiency: η_total = η_pump × η_motor. Typical motor efficiency is 85-95%, so wire-to-water is 60-75%.

How do I convert power between kW and hp?

1 kW = 1.341 hp. For example, 15 kW = 20.1 hp. Conversely, divide hp by 1.341 to get kW. Efficiency is a dimensionless ratio and does not depend on the power unit used.

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Engineering Disclaimer: Calculations are for reference and educational purposes only. Always verify results independently for engineering design. See full disclaimer.
Reviewed by: Industrial Engineering Team
References: ASME B31.3, ASTM A36, Perry's Chemical Engineers' Handbook