On March 8th I added a water heater and have maintained the temperature between 72F - 80F. My utility bill begins and ends on the 20th of each month, so the heater was added midway through the cycle.
The tanks are well insulated R11 and the grow room is insulated at R19. The heater was only required several hours a day. The weather has been slightly warmer than normal, but many days were near freezing and the glazing is not finished so I have a fair amount of infiltration.
All of these variables detract from an accurate assessment, but it is my conclusion that the cost of maintaining the heat for tropical fish and an ideal grow bed temperature is adding about 120 KWH/month or $34/month during the winter.
Recently my efforts have been to cool rather than heat. I'm using an evaporative cooling system which consumes about 180KWH/month at a cost of about $50/month.
My plants were lanky and pale, so on March 18 I added 270W of supplemental lighting, and they have improved. I have also added one more light for the duck weed bringing the total to about 300W.
I have been running the lights for 18 hours a day which is consuming about 5.4KW/day. This additional usage pushed me into the next tier and adds an extra 4 cents per Kilo-Watt, but I'll use my average cost of $0.28/KWH for these calculations. I'd estimate the supplemental lighting adds about 160KWH/month or $45.00/month. I will reduce this or discontinue supplemental lighting when the long Summer days arrive.
In order to reduce costs I'll look into solar or propane heating, and I may be able to reduce the hours I supplement light or find a better glazing design. Currently I have 40 sq ft of South facing vertical glazing in front of 25 sq ft of grow bed. Direct sunlight is cut short by the winter season as well as the solid insulated walls and ceiling.
In addition to lighting and temperature control the pump also consumes about 36KWH/month or about $10/month and tank lights at about 16KWH/month or $4.50
Adding this all up I get
$40.00 - Temperature Control
$45.00 - Lights
$10.00 - Pump
$ 4.50 - Tank Lights
$99.50 - Total utility per month.
I feel the options are:
- Find a way to direct more light onto the grow bed
- Build additional grow beds outdoors for use only in the Summer
- Experiment with less supplemental lighting to find the minimum amount required.
- Change my crop seasonally and switch to cold water fish.
I am currently running the indoor grow room as well as a pond and have begun construction of an outdoor cold water aquaponic system using IBC's. I should be able to compare the costs and production in a few months, but it seems obvious to me that the only way to make aquaponics cost effective is to raise fish that are adapted to your climate and plant seasonal crops.
Even without the additional cost of supplemental lighting my costs would still be about $50.00/month. That is probably a break even point considering the cost of food and other items such as test kits.
I have enjoyed doing this and will continue to look at it as a $1200/year hobby with food as a benefit.
Additional advancement may come from recent technology as found in these links
Solar Grow Tube