Energy formula for each device
Multiply watts by quantity, daily runtime, and days, then divide by 1,000 to get kWh. Multiply kWh by your planning rate for estimated cost.
Enter always-on filters and timed lights as separate devices.
- Energy (kWh) = W × quantity × hours × days ÷ 1,000
- Estimated cost = energy × entered rate
Heater and filter example
A 100 W heater averaging 8 hours daily uses 24 kWh in 30 days. A 10 W filter running continuously uses 7.2 kWh, for 31.2 kWh combined.
At a flat rate of 0.15 per kWh, the simple estimate is 4.68, while a real bill may use tiered household pricing.
Estimating heater runtime
Thermostat heaters cycle off at the target temperature, so entering 24 hours may overestimate use. Consider season, room temperature, lid, and insulation.
A smart plug that records several days of kWh provides a better input when available.
Limits of the estimate
A flat-rate result excludes base charges, taxes, environmental charges, and household tiers. Compare bills or meter readings to isolate the aquarium's real effect.
Do not disable filtration or necessary temperature control solely to reduce the estimate.
Inventory wattage and real operating time
List every powered device—heater, filter, air pump, light, fan, sterilizer, and feeder—and read watts from the device or adapter. Rated output may differ from actual draw, so measure several days with a power monitor when available. Add individual devices or measure the whole strip.
Filters and air pumps often run continuously; lights follow a timer; heaters and coolers cycle with temperature. Treating a 100 W heater as continuously on may suit a winter worst case but overstates normal use. When duty cycle is unknown, compare 25%, 50%, and 75% cases.
- Distinguish label watts from measured average
- Separate continuous and timed devices
- Use duty-cycle scenarios for heating and cooling
Convert to kWh and estimate monthly cost
Daily energy equals watts times hours divided by 1,000. A 20 W filter for 24 hours uses 0.48 kWh per day or 14.4 kWh in 30 days. A 40 W light for eight hours adds 9.6 kWh monthly, making about 24 kWh together.
Multiply total kWh by the entered unit price for a reference cost. A real bill can include tiered pricing, base charges, tax, and seasonal rules. To estimate incremental aquarium use, compare similar-season household bills while noting changes in other appliances.
- kWh = watts × hours ÷ 1,000
- Monthly energy = daily energy × days
- Billing rules can differ from a flat unit price
Estimate heater consumption realistically
Heater use depends on room-to-water temperature difference, tank size, lid, insulation, flow, and ventilation. The same 100 W heater cycles briefly in a warm room and much longer near a cold wall. Measure three to seven days and scale the result rather than relying only on rated power.
Do not reduce cost by abruptly lowering safe livestock temperature or turning off filtration. Start with lids, pipe insulation, reduced drafts, and efficient lighting schedules. Because electricity is close to water, prioritize rated equipment, residual-current protection, splash control, and drip loops.
- Record room and water temperature difference
- Measure 3–7 days and scale to a month
- Prioritize livestock and electrical safety
Use results as a monthly equipment ledger
Record device, watts, daily hours, monthly kWh, and cost, then update summer and winter separately. Comparing totals before and after a proposed device shows its likely running cost. For multiple tanks, keep both tank subtotals and a household total.
When estimates differ from bills, check heater duty cycle, omitted fans or dehumidifiers, timer changes, and kW/W errors. Refresh unit prices from a recent bill because tariffs vary by contract and usage. The calculator does not replace the utility bill or certify equipment safety and sizing.
A power monitor may not capture startup or tiny standby loads perfectly. Multi-day kWh is usually more useful than one instant watt reading; follow the meter rating and electrical safety rules around water.
- Maintain seasonal device records
- Compare incremental cost before adding equipment
- Update inputs from measured use and recent bills