I have the a/c and one computer on the circuit in the shop (its outside). I have two other circuits coming through the wall from the inside of the house running the other three computers. I did it all non-destructively, since I rent. 
Two of my computers only support 4 cards as you can see. The other two support 6 and 7 each. Those small computers are part of the high power ratio. Also the computer rocking 7 cards is all 5830s (@900/300) which are power hungry. That computer is pulling something like 1200 watts IIRC and only getting 2029 Mh/s.
I've been much more concerned with getting my hardware cheaply then getting the setup electrically efficient. Most of the year I welcome the heat anyway. This summer is going to be harder though...
Two of my computers only support 4 cards as you can see. The other two support 6 and 7 each. Those small computers are part of the high power ratio. Also the computer rocking 7 cards is all 5830s (@900/300) which are power hungry. That computer is pulling something like 1200 watts IIRC and only getting 2029 Mh/s.
I've been much more concerned with getting my hardware cheaply then getting the setup electrically efficient. Most of the year I welcome the heat anyway. This summer is going to be harder though...