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Fish Tank Electricity Cost Calculator

Estimate the electricity used by your aquarium heater, filter, lights and air pump. Give each device its own active hours and use your actual electricity price.

Starting inputs are examples. Replace them with your own figures before using the result.

Heater

Average input watts — HeaterActive hours per day — Heater

Filter

Average input watts — FilterActive hours per day — Filter

Lights

Average input watts — LightsActive hours per day — Lights

Air pump / other

Average input watts — Air pump / otherActive hours per day — Air pump / other

Your price and period

Electricity price per kWhPrice entered asCurrency units (e.g. 0.30)Cents / pence (e.g. 30)Number of daysCurrency label

Example price only. Enter your own tariff. Currency is a label, not an exchange conversion.

Enter your figures and select Calculate.

Already measured your aquarium's electricity?

Enter the whole aquarium's measured kWh and the number of days measured. This separate calculation replaces the device estimate above; do not add the two results together.

Measured energy (kWh)Days covered by the readingDays to estimateElectricity price per kWhPrice entered asCurrency units (e.g. 0.30)Cents / pence (e.g. 30)Currency label

Starting values are a teaching example, not an actual reading. The estimate assumes the measured average continues over the chosen period.

Enter a reading and select Calculate from measured kWh.

For example, 9 kWh measured over 7 days averages about 1.286 kWh a day. At the same average for 30 days and an assumed 0.30 per kWh, the energy charge is approximately 11.57 in the chosen currency. Fixed charges, taxes and tariff differences are excluded.

Worked aquarium example

The starting values are fictional: a 100 W heater active for 8 hours uses 0.80 kWh; a 10 W filter for 24 hours uses 0.24 kWh; 15 W lighting for 8 hours uses 0.12 kWh; and a 5 W pump for 24 hours uses 0.12 kWh. Total: 1.28 kWh/day, or 38.4 kWh in 30 days. At an assumed 0.30 per kWh, that is 11.52 in the chosen currency.

Heater hours are not plugged-in hours

A thermostatic heater can remain plugged in while switching its heating element on and off. Enter equivalent full-power heating hours, not automatically 24. If you have measured average power across the full day instead, enter that average and 24 hours. Use one method, not both.

To explore uncertainty, try 4, 8 and 12 heater-active hours with the other example inputs unchanged. The 30-day costs become 7.92, 11.52 and 15.12 at 0.30 per kWh. These are sensitivity examples, not temperature-based predictions.

Keep the tank's needs first

This calculator estimates electricity costs; it does not specify safe temperatures, filtration schedules or equipment sizes. Do not reduce essential heating, aeration or filtration merely to lower a displayed cost. Follow equipment instructions and species-appropriate care. Room temperature, tank conditions and equipment change actual use.

Can I use measured daily kWh instead?

Yes: use the measured-kWh section above with the total reading and the days it covers. Do not add the individual device estimates again. Keep electrical connections dry and use measurement equipment suitable for the installation and load.

Use your own electricity price

Choose currency units for a price such as 0.30 per kWh, or cents/pence for a price such as 30 per kWh. Both represent the same rate. Changing the currency label does not convert money. Fixed charges, taxes and billing adjustments are excluded unless already included in your entered variable rate.

For peak/off-peak or tiered tariffs, calculate each applicable energy block separately. This flat-rate tool cannot reproduce every utility bill. The chosen number of days repeats the same daily pattern; adjust it for weekends, holidays or seasonal use.

Formula and measurement

For each row: kWh per day = watts × active hours ÷ 1,000. Add the rows, multiply by days, then multiply by price per kWh. Use average input power measured at the wall where possible. A suitable energy monitor recording complete-day kWh can be more informative than a short watt reading. Do not double-count equipment included in a whole-system reading.

The US Energy Information Administration explains watts and kilowatt-hours. Read our appliance electricity units guide for another worked example.

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Original calculator and teaching examples prepared 7 November 2026. Calculations run in your browser; this tool does not send your entries to a server. Site advertising and analytics are described in the privacy policy.