Pump Wire-to-Water Efficiency Calculator
Wire-to-water efficiency is the fraction of your electric bill that actually becomes water power. Enter the duty point and metered kW to find it — and what the losses cost.
Wire-to-Water Efficiency
| Item | Value |
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How the calculation works
Water (specific gravity = 1)
Water horsepower = Q (gpm) × TDH (ft) ÷ 3960
Input horsepower = input (kW) × 1.341
Wire-to-water efficiency = water hp ÷ input hp × 100
Wasted power = input (kW) − water hp ÷ 1.341
With motor efficiency given: pump-only efficiency ≈ wire-to-water ÷ motor efficiency × 100
Water horsepower = Q (gpm) × TDH (ft) ÷ 3960
Input horsepower = input (kW) × 1.341
Wire-to-water efficiency = water hp ÷ input hp × 100
Wasted power = input (kW) − water hp ÷ 1.341
With motor efficiency given: pump-only efficiency ≈ wire-to-water ÷ motor efficiency × 100
Notes & limitations
The 3,960 constant converts gpm × ft of water head to horsepower (Hydraulic Institute convention). 1 kW = 1.341 hp.
- The 3,960 constant is for water (SG = 1). For other fluids use water hp = Q × H × SG ÷ 3960.
- Meter the kW at the same operating point as the flow and head readings — efficiency changes across the pump curve, and throttled or VFD operation moves the point.
- Typical wire-to-water efficiency for well-matched pump/motor sets is roughly 50–75%. Persistently low values point to an oversized pump, worn impeller, or a motor running far from its rated load.
- This tool reports overall efficiency only. It does not separate hydraulic, mechanical, and electrical losses without additional measurements.
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