Calculate the daily, monthly, and yearly electricity cost of your aquarium from heater, light, filter, and pump wattages, with realistic heater duty cycles and a quick estimate by tank size.
Aquarium Energy Cost Formula
For the heater, which is thermostat controlled and cycles on and off, the calculator applies a duty cycle instead of assuming full wattage all day:
- C is the electricity cost ($)
- W is the device wattage (watts)
- h is the hours the device runs per day
- d is the number of days (30 for a month, 365 for a year)
- R is your electricity rate ($ per kWh)
- DC is the heater duty cycle (%), the share of the day the heating element is actually on
The full setup mode applies the first formula to each piece of equipment (lighting, filter, air pump, and other gear) and the duty cycle version to the heater, then sums everything into a daily, monthly, and yearly total with a per-device breakdown. The single device mode applies the base formula to one item, which is useful for checking whether a specific pump or light is worth upgrading. The quick estimate mode skips wattages entirely and multiplies your tank volume by a typical average draw per gallon: 1.2 W for unheated coldwater tanks, 3.2 W for heated tropical freshwater, 4.0 W for planted tanks with strong lighting, and 6.0 W for saltwater reef tanks.
Typical Equipment Wattages and Heater Duty Cycles
The first table shows common wattage ranges for aquarium equipment and what each costs per month at the U.S. average rate of about $0.17 per kWh.
| Equipment | Typical wattage | Hours per day | Monthly cost at $0.17/kWh |
|---|---|---|---|
| Heater (thermostat cycles) | 50 – 300 W | 24 (about 45% on) | $2.75 – $16.52 |
| LED lighting | 10 – 60 W | 8 – 10 | $0.51 – $3.06 |
| Filter / return pump | 5 – 80 W | 24 | $0.61 – $9.79 |
| Air pump | 2 – 10 W | 24 | $0.24 – $1.22 |
| UV sterilizer | 8 – 25 W | 24 | $0.98 – $3.06 |
| Wavemaker / powerhead | 5 – 40 W | 24 | $0.61 – $4.90 |
The heater is usually the largest and least understood cost because it does not run continuously. The duty cycle depends mostly on the gap between room temperature and tank temperature. The second table shows realistic duty cycles for a 200 W heater and what each scenario costs per month at $0.17 per kWh, so you can pick the right run pattern in the calculator.
| Room-to-tank temperature gap | Typical duty cycle | Effective draw (200 W heater) | Monthly cost at $0.17/kWh |
|---|---|---|---|
| 2 – 5 F (warm room) | ~35% | 70 W | $8.57 |
| 6 – 10 F (typical home) | ~45% | 90 W | $11.02 |
| 11 – 15 F (cool room) | ~60% | 120 W | $14.69 |
| 16 F or more, or open-top tank | ~75% | 150 W | $18.36 |
Example Problems
Example 1: Itemized tropical freshwater setup. You run a 150 W heater in a typical home (45% duty cycle), a 30 W light for 10 hours per day, a 20 W filter, and a 5 W air pump, and you pay $0.17 per kWh.
- Heater: 150 * 24 * 0.45 / 1000 = 1.62 kWh per day
- Light: 30 * 10 / 1000 = 0.30 kWh per day
- Filter: 20 * 24 / 1000 = 0.48 kWh per day
- Air pump: 5 * 24 / 1000 = 0.12 kWh per day
The total is 2.52 kWh per day, which is an average continuous draw of 105 W. Monthly use is 2.52 * 30 = 75.6 kWh, so the monthly cost is 75.6 * 0.17 = $12.85. Yearly use is 919.8 kWh, or $156.37 per year.
Example 2: Quick estimate for a reef tank. You have a 55 gallon saltwater reef and pay $0.15 per kWh. Using the reef average of 6.0 W per gallon, the average draw is 55 * 6 = 330 W. Daily use is 330 * 24 / 1000 = 7.92 kWh. Monthly use is 7.92 * 30 = 237.6 kWh, so the monthly cost is 237.6 * 0.15 = $35.64, and the yearly cost is 2890.8 * 0.15 = $433.62.
FAQ
Why not just multiply heater wattage by 24 hours?
Because an aquarium heater has a thermostat, it only draws power while the water is below the set point. In a typical home the element is on roughly 45% of the time, so multiplying wattage by 24 hours can overstate heater cost by more than double. If your room stays warm or the tank has a tight lid, the duty cycle drops further; a cool room, an open top, or strong surface agitation pushes it higher because evaporation removes heat quickly.
What uses the most electricity in an aquarium?
In heated tanks the heater is almost always the biggest consumer, followed by lighting. In reef tanks, high-output lighting, return pumps, and wavemakers can rival or exceed the heater, which is why a reef averages around 6 W per gallon while a heated tropical freshwater tank averages closer to 3 W per gallon. Filters and air pumps are cheap to run because their wattages are low even though they run 24 hours a day.
How can I lower my aquarium’s energy cost?
The biggest savings come from reducing heat loss: add a tight-fitting glass lid to cut evaporative cooling, keep the tank away from drafts and exterior walls, and consider insulating the back and sides of larger tanks. Each degree you lower the set point (within the safe range for your fish) reduces heater runtime. Beyond heating, switch older fluorescent fixtures to LED, put lights on a timer at 8 to 10 hours, and replace aging AC pumps with efficient DC models, which often draw half the wattage for the same flow.