What the tank costs to run per month, added up across every piece of equipment.
| Equipment | kWh/month | Cost/month | Share |
|---|---|---|---|
| Heater | 65.8 | $11.18 | 34% |
| Lights | 45.7 | $7.76 | 24% |
| Return pump | 25.6 | $4.35 | 13% |
| Powerheads | 29.2 | $4.97 | 15% |
| Skimmer | 14.6 | $2.48 | 8% |
| Everything else | 11.0 | $1.86 | 6% |
This covers power and salt only. Test kits, food, additives, RO filters, carbon, and replacement equipment usually add as much again. The heater and the lights are almost always the two biggest lines.
kWh/month = Σ(watts × hours per day) ÷ 1000 × 30.44 = 191.8 kWh
Energy is watts times hours. A kilowatt hour is a thousand watts for one hour, so kWh = watts × hours ÷ 1000. Multiply by 30.44, the average days in a month, and by your rate.
Heater duty cycle is the one number people guess wrong. A correctly sized heater in a heated room runs 20 to 40 percent of the time. In a cold garage it can run most of the day, which changes the bill considerably.
LED fixtures draw their rated wattage only at full output. Running at 60 percent intensity draws roughly 60 percent of the power, so a ramped photoperiod costs less than hours times rated watts suggests. The figure here is deliberately conservative.
Pumps draw close to their rating continuously, which is why a large return pump costs more over a year than a large light. A 60 watt return pump running all year is 525 kWh.
DC pumps at reduced speed draw considerably less than AC pumps throttled with a valve. Throttling an AC pump wastes the difference as heat in the tank, which the chiller then has to remove.
Salt cost per gallon is the bucket price divided by the gallons it makes at your salinity, and brands differ by more than the price per bucket suggests. Check the yield, not just the sticker.