The price on the S7's vs the hash rate of the S5 set up on their site is what I was using as a gauge tbh. Three s5+ miners putting out 7.7 TH vs one S7 at 4.5TH. The price difference I think is $600 so not too bad for the extra 3.2TH. I really want to start out with at minimum 20TH. How is the noise and heat factor off of your S5 btw?
I have a area I have made for mining. If you do 20 TH I can tell you from experience if you have hot summer day's you will need to find way's to cool it down. I did it with sheer cfm of lots of fan's and a great exhaust. If you are lucky you climate allows evaporation cooling, mine does not.
Again to do this you really need to know a lot more about your electricity. I knew I had 100 amps just for mining in my mining area. Then another 200 in house if I wanted to put any miners in house.
The only thing i can recommend and what i am setting up for next summer is putting all the exhaust of your miner strait through a window and keep the ambiant temp lower with a strong A/C.
I have mixed results at the moment since i have a very bad A/C, as in the ambient temp is still higher than exterior, but i'm still able to run 7000 watts in a small appartment while keeping the miners in good shape.
At the moment temperature is FINALLY going down, so for the next 8 months i can just keep everything cool by using outdoor temps, but for summer, some good A/C will be required to keep my farm quiet enough.