Enter the electrical input wattage for your heater, lights and pump. Give the heater’s estimated active percentage of a full day, and enter lighting and pump operating hours separately. A heater connected all day does not necessarily heat continuously. Set an absent device’s wattage to zero.
Enter your electricity price in currency units per kWh: for example, enter 0.30 for 30 pence or cents per kWh. The price has no default and must be supplied to calculate cost; all cost results use that same currency. Example equipment values are illustrative, not recommended aquarium settings.
Choose the number of days to estimate. The two fixed reference inputs remain at 1 day and 1 kWh.
For each device, multiply watts by active hours and divide by 1,000 to obtain kWh. Add the three energy amounts, multiply by the number of days, then multiply by your price per kWh. This follows the energy and cost method described by Virginia Cooperative Extension.
The aquarium-specific assumption is that heater active hours equal 24 multiplied by its duty fraction. For example, 25% means six active hours spread across the day; it does not prescribe a six-hour heater timer.
| Scenario | Heater | Lighting | Pump | Daily energy | Daily cost | 30-day energy | 30-day cost |
|---|---|---|---|---|---|---|---|
| Example A | 100 W × 24 h × 25% = 0.60 kWh | 20 W × 8 h = 0.16 kWh | 10 W × 24 h = 0.24 kWh | 1.00 kWh | 0.30 | 30.00 kWh | 9.00 |
| Example B: higher heater duty | 100 W × 24 h × 50% = 1.20 kWh | 20 W × 8 h = 0.16 kWh | 10 W × 24 h = 0.24 kWh | 1.60 kWh | 0.48 | 48.00 kWh | 14.40 |
| Example C: no heater | 0 W = 0.00 kWh | 20 W × 8 h = 0.16 kWh | 10 W × 24 h = 0.24 kWh | 0.40 kWh | 0.12 | 12.00 kWh | 3.60 |
Allowed inputs are 0–10,000 W per device, 0–100% heater duty, 0–24 operating hours per day for lights and pump, 1–3,660 whole days, and a nonnegative electricity price up to 10,000 currency units per kWh. These are calculator limits, not equipment or animal-care recommendations.
The estimate assumes constant power while each device is active, zero power while inactive, the same daily schedule throughout the period and one electricity price. Heater duty is supplied by you; the calculator does not predict it from tank volume or temperature. Changing room conditions, thermostat cycling, dimming, variable-speed pumps and standby consumption can change actual use. A measured average wattage should not also be reduced by a duty factor that already accounts for the same cycling.
Only the three entered loads are included. Fixed electricity charges, tariff tiers and time-of-use variation are excluded. Use 30 days for a 30-day estimate or 365 for a 365-day estimate; neither automatically predicts seasonal changes. A missing price leaves cost unavailable, not zero. Zero price is accepted only when intentionally entered. Invalid or out-of-range results must not be interpreted as zero.