My bill went up 90$ US after adding a single 1,000 watter. Now I'm running about 3,000 watts of HPS @ 12/12 and about 1,200 watts of T5HO @ 24/0 and my bill is about 410$ a month. Also, there are about 8 box fans and 3 inline sixxers hooked up as well as a 10,000 BTU a/c, pumps, etc.