Aquarium Running Cost Calculator
Add up what your tank actually costs each month: always-on equipment like filters and pumps, lights on their photoperiod, the heater's real duty cycle, and optionally the water for your weekly changes.
The 30% heater duty cycle is a starting estimate — actual runtime depends on how far room temperature sits below your target (a cold basement can push it past 50%; a warm room in summer can drop it near zero). Salt mix for marine tanks isn't included.
Where the money actually goes
For most heated tanks the heater dominates the electricity bill, but not because of its headline wattage — a 150 W heater doesn't draw 150 W around the clock. It cycles on and off to hold temperature, and its duty cycle depends on the gap between room and water temperature. In a comfortable living room 30% is a reasonable estimate; in a cold basement it can exceed 50%, and in a warm summer room it can approach zero. Filters, return pumps, and wavemakers are smaller draws individually but run 24 hours a day, so their totals add up more than people expect.
Water is usually the cheap part on municipal supply — the US average works out to roughly half a cent per gallon — but it's worth counting if you buy RO/DI water or run large tanks with big weekly changes. This calculator uses the same energy model as the AquaLens app's equipment dashboard, which computes it automatically from your logged hardware and even estimates the heater duty cycle from your room and target temperatures.