Reef tank electricity cost calculator
Most UK articles still use the 2022 price cap. Work out what your pumps, light, heaters and skimmer cost to run at today’s price, and which one costs the most.
Formulas and sources last checked . How we check
Calculator
Result
A month£31.34
- A year
- £376
- A day
- £1.03, 3.91 kWh
- Biggest user
- Heaters (average), 37 per cent
Electricity only. Salt, RO/DI cartridges and waste water, test kits, food and replacement kit come on top.
How much does a reef tank cost to run in the UK?
Each device uses its average watts times its hours a day, divided by 1,000, in kilowatt hours (kWh). Add them up and multiply by your unit price. For a heater or a light that dims, use the average, not the label: a 200 W heater that is on a third of the time averages about 67 W. The daily standing charge is left out, because you pay it with or without a tank.
kWh a day = sum of (watts x hours) / 1000cost a day = kWh a day x pence per kWh / 100cost a month = cost a day x 365 / 12
Worked example: a 200 litre mixed reef
- Return pump 30 W, two wavemakers at 15 W and a skimmer at 15 W, all day: 75 W x 24 = 1.8 kWh.
- A 100 W LED at 75 per cent for 9 hours: 0.68 kWh. Heaters averaging 60 W: 1.44 kWh.
- About 3.9 kWh a day. At 26.32p, that is about £1.03 a day, £31 a month or £376 a year, before salt, RO water, tests and food.
These are our estimates for a typical set-up; a plug-in energy meter on your own tank gives the real figures.
Why do other guides give higher costs?
Practical Fishkeeping’s electricity guide works through a 120 cm tank at £25.06 a month at 34p per kWh, the 2022 to 2023 cap. The Ofgem cap for 1 October to 31 December 2026 is 26.32p per kWh (seen in a search summary of Ofgem’s notice), so the same tank costs less to run now. Prices change every three months; update the price above from your bill.
What are the limits?
Other calculators
- Salt mixGrams of salt for a batch, and what your refractometer or hydrometer should read.
- Salinity correctionHow much water to swap, day by day, at a safe pace.
- Water change effectWhat a change, or a run of changes, does to a reading.
- ATO reservoir safetyHow far salinity falls if a stuck pump empties the reservoir.
- Dosing from a test resultMillilitres to bring alkalinity, calcium or magnesium back to target.
- Daily consumptionHow much your tank uses a day, and the daily dose to match.
- Unit converterdKH, meq/L, ppm, SG, ppt, litres and gallons, Celsius and Fahrenheit.
- Tank volumeLitres from the tank size, and the net water after rock, sand and sump.
- Heater sizeWatts for a UK room, split across heaters so one stuck on is not a disaster.
- Light hours and PARPhotoperiod, ramps, daily light and PAR by coral group.
- Stocking and compatibilityCheck a list of fish against each other, the tank and your corals.