Low-energy pond pump: how much does it really cost in electricity?

A filter pump runs 24 hours a day, often from March to November, sometimes all year round. It is the appliance that weighs most heavily on a pond's electricity bill. Before you buy, or to find out whether it is worth replacing an old pump, here is how to work out what it really costs you.

Calculating the cost of your pump

Take the power rating in watts shown on the label or in the manual. Example for a 100 W pump running all year round:

• 100 W × 24 h × 365 days ÷ 1,000 = 876 kWh per year.
• At €0.35 per kWh, that comes to about €300 a year.

Replace €0.35 with the price in your contract. Over ten years, an energy-hungry pump can cost far more in electricity than it did to buy.

Standard or low-energy: the difference

Indicative example: always compare at the same flow rate and at the head height of your own installation. In this example, the saving exceeds €180 a year.

What really drives a pump's consumption

• An oversized flow rate: the usual rule is to pass the entire pond volume through the filter in 1 to 2 hours, more often for koi. Beyond that, you are paying for nothing.
• Head height and hoses: a hose that is too narrow or too long reduces the actual flow rate, and people compensate with a more powerful pump.
• A clogged intake strainer: the pump strains and delivers less.
• Motor technology: modern permanent-magnet motors with adjustable speed use much less power.

Also worth reading

To choose the right flow rate before comparing consumption, read How to choose a pump for your pond?.

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Should you replace an old pump that still works?

Do the maths: if the annual saving covers the price of the new pump within two to four seasons, replacing it pays off, even if the old one is still running. It is also a chance to review the flow rate you actually need.

Calculating over your actual season

The 365-day calculation gives the maximum. If you switch off filtration over winter, redo the formula with your actual running period. From March to November, count roughly 275 days:

• 100 W x 24 h x 275 days ÷ 1,000 = 660 kWh, or about €231 at €0.35.
• 40 W x 24 h x 275 days ÷ 1,000 = 264 kWh, or about €92 at €0.35.

The difference remains clear over a single season: about €139 a year in this example, versus €184 over the full year. Remember to add everything up: the pump is not alone on the circuit. A UV lamp, an aerator or a skimmer also use power. For example, a small 8 W aerator adds about 70 kWh over a full year, and a 36 W UV about 315 kWh. For aeration, see also How much power does a pond aerator use?

The right flow rate before the right model

This is the simplest lever: a properly sized pump saves you paying for power you do not need. Apply the rule from this article, which is to pass the pond volume through the filter in 1 to 2 hours. For a 10 m³ pond with goldfish, you therefore aim for 5,000 to 10,000 litres per hour at the filter, more with koi.

Be careful with the advertised figure: the flow rate on a product page is a maximum, measured with no head height and no hose length. As soon as the water has to rise to the filter, the actual flow drops. So choose from the flow curve, at your head height. Our pump and filter flow rate table helps you make that choice.

Comparing two pumps the right way

• Look at the flow rate at your head height, not the maximum flow rate.
• Divide that flow rate by the watts consumed: you get the litres moved per watt, a directly comparable figure.
• Check that the pump can handle the debris in your installation.
• Look at the safety features, such as dry-run protection.
• Compare the total cost over several seasons, not just the purchase price.

Frequently asked questions

— Can I switch the pump off at night to save money?

No, unless the pond has no fish. The filter bacteria need a continuous flow of water, and night is when oxygen is in shortest supply.

— Is a variable-speed pump worthwhile?

Yes: you reduce the flow in winter or when the pond has a light load, and consumption drops accordingly.

— What about a solar pump?

It suits small ponds without fish or water features. For continuous filtration, a mains-powered eco pump remains more reliable.

In summary

• Annual cost = power × hours × days ÷ 1,000 × price per kWh.
• An eco pump with the right flow rate often pays for itself within a few seasons.
• A suitable flow rate and wide enough hoses matter as much as the pump.

Last updated: 27 September 2026.