0.13 USD per KWH
If your power is over $0.10 I would not recommend getting into the Bitcoin mining business, at least not for now.
Antminer S5 can get you 1.15 TH/s with about 600W of power usage. Your power costs would be about $56.00 per month and your monthly profit would be only $25.00 based on the current Bitcoin rate and difficulty. This month the difficulty is expected to increase, so your profit would even decrease.
You can use the profit calculator here - http://www.coinwarz.com/calculators/bitcoin-mining-calculator/?h=1155.00&p=600.00&pc=0.13&pf=0.00&d=47610564513.47130000&r=25.00000000&er=221.98970000&hc=400
You probably won't even get the money back for the hardware you would spend.
was about to say that's not cheap at all . for that many miners to be safe he would need a building out side his home or i would, one with 3 240 lines at 50 amps or better and at least two 120 lines for external add ons to plug in stuff to be safe, would even need a business account in my state for that much power usage per month which is cheaper then homes get here. I'm at 8.55 cents per KWH to me that's to much compared to some in US at 4 cents per kwh .Id kill for that if i could get it and not move to Washington state.
SO to the OP bear in mind if you plan to run that many in your home there is a lot more involved then just plugging that many miners in your home .if that's the plan, but then there that's poss of blocks being hit sooner and faster with that much hash pumping out all the time
.difficulty in 6.5 days: 48882648479.1 or less so not to bad but still the power cost would be a nite mare for me .