Doing a little math to see what it costs to run my tank...
3 MH bulbs - 900w x 6 hrs per day
2 VHO bulbs - 187w x 11 hrs per day
Return pump - 141w x 24 hrs per day
3 Vortech pumps - 63w x 24 hrs per day
Calcium Reactor - 65w x 24 hrs per day
3 Fuge lights - 62w x 8 hrs per day
2 Skimmer pumps - 116w x 24 hrs per day
Prop light - 147w x 7 hrs per day
2 Icecap Fans - 12w x 7 hrs per day
All of the above runs 19.3 kWh per day, or 579 kWh per month.
Take that number times $.124375 and it adds up to $72 of basic operational cost.
Not included are a handful of tiny pumps running the suncoral tank, phosban reactors, flow in the prop section and refugium, which is probably around 100w for about $9 a month more, which puts the tank at $81.
In the winter, I run a couple of heaters which definitely cost me money. I only use two and they don't have a lot of wattage, thus they run longer than they should have to trying to bring the tank temperature up to 79.5 so they can shut off again. I probably need two 500w heaters so they can do the job quickly and save money, but what I have is a 300w & a 250w heater. That's something I'll need to resolve this fall, and make sure the DJ power strips can handle the extra wattage load, if they were to kick on during the lighting period. For now, the heaters are turned off for the summer months. My tank doesn't drop below 78.5F at night.
The window A/C unit definitely adds to the monthly expense during the hot months. If the circulation fan is running, it uses 116w of power. When the compressor kicks on, it uses 727w. If the garage is closed, it works even harder and uses something closer to 780+w of power. Last year, I measured the window A/C with a Kill-o-watt for two weeks straight to find out how long the compressor was on versus how long just the circulation fan was running, and it was pretty much 50/50. I hate to even calculate this one. 303 kWh equaling $38 a month.
During June, I was been able to turn off the window a/c during the late night hours, and turn it on daily around 1pm. One day I forgot and didn't turn it on until 3:30pm, after the lights had been on for some time and the fish room was getting toasty. However, the tank was 79.8F, which is due to the fact that my lights are 18" off the water. I don't really want to test the theory of what will happen if the A/C unit is off for the full day with the fish room closed up, but I do have the Aqua Controller II set to turn off the lights if the tank reaches 83F.
Add on the live rock cooking vat and the quarantine tank of 36 kWh and the angled tank of 73 kWh, and it looks like my little hobby is soaking up 1063 kWh per month, which is about $132 per month. My electricity rates are about to jump up slightly, which will put it around $149 per month in total electricity usage.
My three Vortechs combined use $5.64 of electricity a month to provide all the flow in my reef. The one Vortech on the angled tank costs $0.62 a month at a mere 6 watts of power. :)