Where I live, it's still hot enough outside to require running the A/C, so until it gets colder outside, any additional heat produced by my rig is an additional cost, because the A/C has to run that much more.
This. Man i'm considering in splurging on a bigger A/C to compensate for the added heat in my "computer room", it is currently running for 16h a day so i can survive this heat, that's 21KW/h a day and my humble 4 card rig is using 21.6KW/h a day, thats 42.6KW/h to generate 0.5BTC on average. Thank God in Venezuela we pay $0.011 per KW/h
