How Much Does It Cost to Run a Water Pump?

Most household pumps have a motor of 0.5 HP (0.37 kW) to 1 HP (0.75 kW). That rating is the motor's output. The pump draws more than that from the socket, because no motor is 100% efficient.

Pedrollo, for example, rates its 0.75 HP PKm 65 pump at 3.7 A and its 1 HP PKm 80 at 5.2 A on 230 V: up to about 850 W and 1,200 W from the socket. We use 750 W as a typical figure.

At 1 hour a day that's 0.75 kWh: about Rs 25 a day in Pakistan, $0.14 in the US and £0.20 in the UK. Over a month it comes to about 23 kWh, or Rs 755 in Pakistan.

In Pakistan, India and Bangladesh, a water motor usually lifts water from the mains supply or an underground tank to a tank on the roof. Rooftop tanks are also common across the Middle East, Africa and Southeast Asia, wherever mains pressure is low.

The cost depends on how much water you pump and how high. A 0.75 HP pump such as the Pedrollo PKm 65 moves about 1,800–2,400 litres an hour against 17–27 m of head (the height plus pipe friction it pumps against). It fills a 1,000-litre tank in roughly half an hour.

The higher the tank and the longer or narrower the pipes, the slower the flow. The motor then runs longer for the same amount of water.

Self-priming mini pumps sold in India, such as CRI's Selfy range, come in 0.37–0.75 kW (0.5–1 HP) sizes for a 220–240 V single-phase supply.

Elsewhere, pumps more often boost the water pressure in a home, draw water from a rainwater tank, as in much of rural Australia, or supply a private well, as in rural North America.

A pressure pump starts whenever a tap opens, so it runs in many short bursts. Its total running time depends on how much water you use, not on the clock.

Variable-speed boosters slow down when demand is low. Grundfos rates its SCALA2 3-45 at up to 550 W, but its published curves show it drawing well under 100 W at its lowest speeds.

In 120 V countries such as the US and Canada, a pump draws about twice the current of a 230 V pump of the same power. The cost depends only on the watts and the hours.

A pump's HP or kW rating is its motor's output. For the power it draws, look for the input power (P1) on the label, or multiply the volts by the amps for an upper limit. Use that figure and your own daily running time in the calculator.

• Fit a float switch or an automatic controller so the motor stops as soon as the tank is full, with no overflow.
• Fill the tank in one run rather than several short ones.
• Fix leaking taps, pipes and toilet valves. With a pressure pump, every leak makes the motor restart.
• Never let the pump run dry. It wastes power and can burn out the motor; many pumps offer dry-run protection.
• Keep pipes as short and straight as you can, use the pipe size the manual recommends, and clean the suction strainer.
• If you have solar panels or a time-of-use tariff, fill the tank in sunny or off-peak hours.

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