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Monthly cost of running a home water pump from its horsepower, motor efficiency, tank size and daily fills.
This calculator works out what a domestic water pump costs to run by separating two things people usually confuse: the horsepower on the nameplate is shaft output, while the meter records motor input, which is higher by the motor's efficiency. A 1 HP pump at 72% motor efficiency draws about 1.04 kW, not 0.75 kW. Runtime is derived from the physical job — tank litres divided by flow rate — and the pump equation (density × 9.81 × flow × head) checks how much of that electricity actually becomes lifted water.
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Costing a 1 HP pump at 746 W understates the bill by nearly 40% — motor efficiency is applied explicitly.
A per-kilolitre figure lets you compare pumping cost directly against a tanker delivery or a borewell.
Wire-to-water efficiency flags an oversized pump, a choked foot valve or an undersized delivery line.
About 1.04 units an hour, assuming a typical single-phase motor efficiency of 72%. The arithmetic is 1 HP × 745.7 W ÷ 0.72, which comes to 1036 W — the 746 W figure people quote is the shaft output, not what the meter sees.
Roughly 17 minutes at a flow of 60 litres a minute, which is typical for a 1 HP pump lifting to about 25 metres. Flow drops sharply as head rises, so the same pump on a fifth floor may need twice as long — time one fill with a stopwatch to get your real number.
Per hour, yes, in almost direct proportion to horsepower. Per tank filled, not necessarily: a larger pump moves the same water in less time, so if the flow rises proportionally the energy per thousand litres barely changes. An oversized pump only wastes money when it is throttled or runs far off its best efficiency point.
Three reasons, in order of how often they apply: the nameplate figure is shaft power and the motor adds its own losses; low supply voltage makes the motor draw more current for the same work; and a worn impeller, choked strainer or partly closed valve pushes the pump off its efficiency curve so it runs longer for the same tank.
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