If you’re wondering why the electricity bill goes up when you add a fountain, filter or waterfall, the answer comes down to three things: the pump’s wattage, how many hours it runs and the resistance (head and plumbing losses) the pump works against. This article shows the simple maths to turn watts into pounds, uses real pump examples to give a sense of likely running costs, and explains how pump selection, installation and extra equipment (filters, UVCs) affect your total energy use.
Short answer
It depends — watts, hours and how hard the pump works
A pond pump's electricity use depends on its power rating (watts), how many hours a day you run it, and how hard it has to work to move water (the pump’s operating point, which depends on flow and total dynamic head). Small feature pumps can draw only a few watts; larger pond and fountain pumps can draw tens or even over a hundred watts. Add filters, UVC clarifiers and any other electrically driven equipment, and you have the pond’s total running cost.
Below is a simple calculation to convert pump watts into kilowatt‑hours (kWh) and cost, followed by worked examples using real product power figures so you can see typical monthly figures.
The simple maths
How to calculate kWh and cost (worked examples)
Use this straightforward method:
1) Convert watts to kilowatts: watts ÷ 1,000 = kW.
2) Multiply kW by hours run = kWh used.
3) Multiply kWh by your electricity unit price (£/kWh) = cost.
Formula (hourly): cost per hour = (£/kWh) × (watts ÷ 1,000). Monthly cost = hourly cost × hours per month. For continuous 24/7 running, a typical month uses about 720 hours (24 × 30).
Worked examples (using manufacturer power figures):
Aquarius Eco Premium 6500 — manufacturer lists power 15–55 W. At 15 W: 0.015 kW × 720 h = 10.8 kWh; at 55 W: 0.055 kW × 720 h = 39.6 kWh. Using £0.30/kWh as an example electricity price, those monthly costs would be about £3.24 (15 W) and £11.88 (55 W).
AquaMax Eco Premium 17000 — listed 18–140 W. At the low end, the monthly cost is small; at the high end, it is substantially larger. This illustrates how the same pump family can have a very different draw depending on the operating point.
PondJet Eco Premium (floating fountain) — listed at 150 W. Example: 0.150 kW × 720 h = 108 kWh per month; at £0.30/kWh that’s about £32.40/month.
FiltoMatic CWS 14000 (filter with UVC) — filter 27 W + UVC 24 W = 51 W continuous nominal; cleaning cycle peaks at 54 W. At 51 W continuous: 0.051 kW × 720 h = 36.72 kWh → about £11.02/month at £0.30/kWh. The manufacturer also highlights demand‑driven UVC control that can reduce running hours and save energy.
Note these are worked examples using published product wattages and an example unit price. Your actual cost depends on the pump’s operating point (where it sits on its flow/head curve), how many hours you run it and your local electricity tariff.
Performance matters
Flow, head and efficiency — why a pump’s draw can change
A pump’s labelled wattage is not a single fixed number in normal use. The electrical draw depends on the flow it must deliver against the pond’s total dynamic head (TDH) — the vertical lift plus friction from plumbing, fittings and filters. The harder the pump has to work, generally the more power it draws.
Manufacturers provide pump curves showing flow versus head; selecting a pump that operates near its best‑efficiency point gives the most litres per kWh. Oversizing a pump can waste energy if you throttle it back with valves; undersizing can overwork the unit and shorten its life.
For help matching flow and head to your pond layout see PondStuff’s guides on pump flow and head: Pond pump flow rate explained and Pond pump head height explained, and our note on choosing a pump size: What size pond pump do I need?.
All the bits add up
Include filters, UVCs and extra pumps in your running cost
Don’t forget that the pump is often only part of the electrical picture. External filters with integrated pumps, separate filter pumps, UVC clarifiers and automatic cleaning cycles all add to consumption. The FiltoMatic example above shows the combined power of a filter and UVC — and that a cleaning cycle can temporarily increase draw.
Some modern units have demand‑driven controls or timers, so the UVC or cleaning function runs only when needed; the manufacturer of the FiltoMatic cites “up to 40%” energy savings when the UVC runs on demand compared with continuous operation. That is a manufacturer claim for that product — similar smart control can reduce overall energy use on other systems too.
When budgeting, add the wattage of every electrical device that runs with the pump rather than assuming the pump is the only load to count.
Pond type matters
Ornamental, fish and wildlife ponds — different needs and costs
How much you need to circulate and filter water depends on the pond’s purpose.
Wildlife ponds: these often don't require pumps or filters—simpler, passive systems are often best for amphibians and invertebrates. If you do add a pump (for a small water feature or shallow cascade), keep it low impact, protect intakes so frogs and tadpoles can’t be sucked in, and use power only when necessary.
Ornamental garden ponds: moderate circulation can help reduce blanket algae and duckweed. As a rule of thumb cited by conservation bodies, circulating roughly half the pond volume per hour is often effective against many algal species — use this carefully as a guideline rather than an absolute rule. If you aim for a specific turnover, choose a pump capable of that flow at your actual head.
Fish and koi ponds: ponds containing fish generally need robust filtration and reliable circulation to maintain oxygen and water quality; that usually means larger pumps and possibly multiple pieces of equipment, so running costs tend to be higher. Because goldfish and koi systems have different needs, consult specialist guidance and manufacturer sizing information when planning koi pond equipment.
Our Pond Volume Calculator can help you estimate how much water you have to circulate: Pond Volume Calculator. Also see Do I need a pond filter? if you’re unsure whether a filter is required for your pond type.
Practical savings
Ways to reduce pump electricity use without risking pond health
Small changes to how you size, install and run a pump can make a noticeable difference to energy use:
Choose the right pump size for the required flow and head required —avoid wildly oversizing. See What size pond pump do I need?.
Reduce head losses with smooth, straight pipe runs, correctly sized pipework, and minimal restrictive fittings. Less friction means the pump works less hard.
Where appropriate, use a variable‑speed or ‘eco’ pump and run at the lowest speed that still meets your circulation needs; many modern ‘eco’ pumps are designed to be efficient across a range of flows.
Time or reduce pump run hours if you don’t need 24/7 operation — see our guide Should you run a pond pump 24 hours a day? for when continuous running is helpful and when you might reduce hours safely.
Keep pump and filter clean and service them regularly — blocked intakes and dirty impellers reduce efficiency and increase draw.
Consider demand‑controlled UVCs or timers for cleaning cycles rather than continuous operation.
When adding a waterfall or decorative feature, read the advice on pump selection for falls — features often require more head and thus more power: How to choose a pond pump for a waterfall.
These adjustments can lower your electricity use while keeping water quality and fish welfare intact.
Safety first
Electrical installation and legal considerations
A qualified electrician should install any permanent electrics for a pond—fixed sockets, buried cabling, or mains connections. Connect outdoor equipment to a suitable residual‑current device (RCD) and use outdoor‑rated cable and fittings. Follow the pump manufacturer’s installation instructions, including specified cable lengths and whether the pump may be operated submerged or only dry.
Planning and safety also mean checking for buried services before digging and observing guidance about working near overhead power lines. If wildlife uses your pond, take extra care over intake protection so animals aren’t harmed.
Do not attempt non‑qualified electrical work yourself; incorrect wiring risks electric shock and appliance damage, and can endanger pond wildlife and fish if circulation fails.
When to call a pro
Get expert help with complex systems or persistent problems
If you have a large koi system, multiple pumps, an automated filter with UVCs, or you’re getting unexpectedly high electricity bills, it’s worth asking a pond specialist or the pump manufacturer for help. A professional can calculate the total dynamic head for your plumbing layout, recommend a pump that runs near its best‑efficiency point, and advise on controllers or variable‑speed drives that could save money.
If you suspect your pump is underperforming or overheating, switch it off and ask a technician to inspect it — failing pumps can cause water‑quality collapses that affect fish. For safety or wiring concerns always use a qualified electrician rather than attempting DIY fixes.