Check out your previous electric bill to find out how much you are being charged per kilowatt-hour... ~12 cents is average in the U.S. Mars600 uses 278 watts. We will just say you have 1 running 24 hours (instead of 2 running 12 hours). 278/1000 = .278 kW so now we need to now multiply that .278 by 720 because we will be running .278 kW for 720 hours a month (30days x 24 hours = 720 hours) so now we're at 200.16 kWh/month multiply that by 12 cents because we're being charged 12 cents per kilowatt-hour and you're at $24 a month.
no problem. interesting video i just found talking about energy consumption ... most interesting was the "gas lamp routine" thing for vegging.
Now our tech had update the true watt of Mars 300 and 600. the actual watt of mars 300 is about 120w, the 600 is about 240w