exelent calculations, so this means you have found a very good way to earn out of mining, which miners do you use ?
GPUs :p
I assume you are not going to be mining bitcoin with this setup (likely will use a multi pool with scrypt based coins or some other algo).
I would not at all be surprised to see the difficulty increase as a faster pace this winter as people start to use their ASICs that are no longer energy efficient enough to mine more BTC then they cost in electricity again to help heat their home.
That might be true if the older machines had some relevance. I replaced 5 BFL Singles doing 300GH/s and pulling 1500 Watts with just 1 Antminer S3 doing 450GH/S with just 350Watts.
Even if every Avalon, BFL, AM Blade and block eruptor came back online it would be less than 10PH/s.
Also as winter comes to the north, southern hemisphere like Venezuela with cheap power goes to summer - so minimal season effect.