Build a transparent daily and annual running-cost scenario using your own equipment and tariff.
A thermostatic heater is not normally drawing its rated wattage every minute. Duty cycle matters, while filters commonly run continuously and lights run for a chosen schedule. This tool keeps those patterns separate.
A 150 W heater active 35% of the time averages 52.5 W across the day. Add a 12 W filter running continuously and a 25 W light for eight hours, then apply your own tariff.
Changing heater duty cycle, tariff and lighting hours makes the biggest assumptions visible.
Room temperature, lid design, airflow, target water temperature and season can change heater run time. A plug-in energy monitor is more reliable than an estimate when you need measured consumption.
Air pumps, UV units, wavemakers, dosing equipment and smart-plug standby use are not included unless you add them elsewhere. The result is a planning scenario, not a utility-bill guarantee.
Start with the wattages printed on your equipment and your own electricity tariff. The weak point is usually the heater duty cycle: a thermostatic heater switches on and off, so it rarely behaves like a device drawing its full rated wattage every minute of the day.
If running cost matters, a plug-in energy monitor can replace the duty-cycle guess with a measured figure. Recheck in a colder period as room temperature changes how hard the heater works. Variable-speed pumps and dimmable lights can also use less than their label maximum depending on their settings.
Standing charges are excluded because they are household charges you pay regardless of the aquarium. Additional equipment such as air pumps, UV units, dosing pumps, CO₂ solenoids, wavemakers or chillers should be added separately if they are significant.