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Calculating the Costs Aquarium.Net Oct 96

Dana Riddle takes you through the costs of running an aquarium with this handy worksheet, Oct. 1996 Index for Aquarium Net, Aquarium Net has numerous articles written by the leading authors for the advanced aquarist

Calculating the Costs

by Dana Riddle

It is often said that the good things in life are free. Aquarists, knowing that their aquaria are one of the good things, will likely disagree. Although they know well that an aquarium can be enjoyable and enlightening, it would be a disservice to say it is free. In fact, a full-blown reef aquarium can be down-right expensive.

When the aquarium and related equipment is purchased, understanding the cost is easy. Most of us practice price-comparison shopping. Not so obvious are the operating costs, more specifically, those monthly charges you'll pay to your electric utility each month. When considering the operating costs, that powerhead you purchased for, say, $29.95 may not be the bargain it appears to be. A more expensive unit might cost more but could be less expensive to own over the equipment's lifetime. The same can be said for system pumps - those that provide water flow to the aquarium or its filtration system. For example, I compared the operating cost of 3 different pumps being used or sold at a local shop. I won't mention brand names, but these are the actual operating costs per day:

Pump A - 38 cents per day

Pump B - $3.25 per day

Pump C - $1.32 per day

Its pretty obvious that just buying any pump without comparing electricity consumption can be an expensive mistake.

At the end of this article, I'll have a short estimation chart for your use. The "average" reef aquarium will probably use an "advanced" lighting system, a circulation pump, a powerhead or two, a heater and maybe a chiller. We'll examine the costs associated with this equipment after a quick review of terminology.


An in-depth class on electrical terms and meanings is beyond the scope (and my capabilities) of this short article. However, the hobbyist should be familiar with the terminology and be able to use conversion factors.

Power companies charge you by the kilowatt hour (abbreviated as kwH). A 1,000 watt light bulb burning for 1 hour uses 1 kwH. Prices vary for a kilowatt-hour. Here in the Atlanta area, residential customers pay 10 to 12 cents per kwH. Industrial users may pay as little as 2 cents per kwH. Many utilities state your cost per kwH on your bill, if not, divide your bill (less tax) by the number of kwH used to arrive at your cost.

Some equipment will not list its wattage on the information plate. All is not lost, however. If the plate lists the amperage and voltage, use this formula:

Amperage X voltage = wattage

For example, a pump pulling 4 amps at 115 volts uses 460 watts.

If horsepower is all that is listed, use this formula:

Horsepower X 0.75 = kilowatts

For instance, a chiller listed at 1/4 (0.25) horsepower = 0.25 X 0.75 = 0.1875 kw or 187.5 watts.


Estimating your lighting cost appears to be straight forward. In reality, it gets pretty complicated when we consider ballast efficiencies. Electronic ballasts are usually more efficient than tar ballasts - we'll leave it at that. For estimating costs, use the total bulb wattage times the hour of hours they are on. For example, an aquarium might use 1 - 175 watt metal halide bulb for 10 hours and 2-110 watt VHO florescent bulbs for 12 hours.


175 watts X 10 hours = 1,750 watts = 1.75 kwH

2 X 110 X 12 hours = 2,640 watts = 2.64 kwH

Total kwH = 4.39 kwH per day X 10 cents per kwH = 43.9 cents per day to operate.

Some lighting systems use a small, computer fan for cooling. Be sure to include this wattage in your estimations.

System Pumps

Pumps can be the largest power consumer of any single piece of equipment in an aquarium system. Shop wisely when purchasing a pump. However, don't make a purchase based entirely upon purchasing price or operating cost. If the pump is noisy and operates an aquarium in your bedroom, both the pump and your spouse may not let you get any sleep. Spare parts availability should also be examined. So, several factors should influence your decision. Just be aware that, as seen in our example above, operating a pump could cost over $100 monthly.


These small, submersible centrifugal pumps are often used to provide circulation in a reef aquarium. Generally, these are much less expensive to operate than system pumps. But be sure to do your homework.

Check the gallons-per-hour rating and divide by wattage to determine the most cost-efficient powerhead. In some cases, it is better to buy a larger powerhead that is capable of being throttled.


Heater selection is usually made on a watts-per-gallon estimate. There are many problems with this simple guide (for reasons beyond the scope of this article). If the heater is of more wattage than actually required, the heater will cycle on and off many times during the day. This can lead to premature heater failure. On-off cycles should be minimal. It also makes it much easier to estimate electrical cost.


As with heaters, chiller selection is usually based on a delta temperature requirement which cannot possibly include every particular of your aquarium. Chiller on-off cycles should be minimal as well or you'll be replacing an expensive compressor with distressing regularity. Chillers are generally rated by horsepower; use the conversion factor listed earlier in this article.

Other Equipment

Don't forget to evaluate other devices - wavemakers, self-powered protein skimmers, ozonizers, etc. These can add up to a substantial amount of power!

Estimation Sheet


Metal Halides:

Total wattage ____ X ______ "burn" time (hours) = _____ Æ 1,000 = _______ kwH


Total wattage____X____"burn" time (hours) = ______ Æ 1,000 =_____ kw

Cooling fan:

Wattage_____ X run time (hours) = _______ Æ 1,000 = _____ kwH


Wattage X 24 hours (or best estimate) = ______ Æ 1,000 =______kwH


Wattage X 24 hours (or best estimate) = ________ Æ 1,000 = ______ kwH

System Pump:

Wattage X 24 hours = ________ Æ 1,000 = ______ kwH


Wattage _____ X ____ number of powerheads X 24 hours (or best estimate) = ____kwH Æ 1,000 = _______ kwH

Miscellaneous Devices

Total wattage X 24 hours (or best estimate) = ______ Æ 1,000 = kwH

Total kwH _______ X ______ (cost per kwH) X 24 = _____ Cost per day

Now that you've completed this exercise, you can either show or hide (just kidding) the answer from your spouse. If you're considering the latter choice, perhaps a reevaluation of your equipment choices is in order.

Created by liquid
Last modified 2006-11-20 03:04