OK, I live in California, have been Bitcoin mining since late June / early July, was (at one point) sucking about 40 Amps (20 from one circuit and 20 from another) to power a total of 8 mining rigs, subsequently got kicked out of the single room office I had been renting (not just for Bitcoin mining), now I'm mining in another rented office on only 3 rigs. It's still hot in there :-)
I kind of doubt that anybody reads this...
That June/July period would have been very profitable for your 7.5GHash/s system ...
Initially I had only a 2 GHash setup, give or take, and was still in the process of building rigs when the Bitcoin exchange rate plummeted to $3.
I think I spent between 4 and 5 grand on hardware, but recouped only about 1 grand by selling Bitcoins. In the end I had a 5 GHash setup consisting of 8 computers, most (but not all) of them with 4 graphics cards in them, most (but not all) 5830 cards. Some cards were 6790 cards (a waste of money). I did not overclock, but still encountered cooling problems. This party ended when they gave me a 3 day notice to vacate due to "breach of contract", using the office for other purposes than is written in the [boilerplate] lease contract. I complied with the 3 day notice, since my lease had just expired and the contract did say "no right to holdover". So, legally, I was on very thin ice there.
And I continued to suffer from MASSIVE outages, either due to DDoS on the mining pools I was mining at, or due to the Comcast cable connection throttling, or whatever. I was constantly switching mining pools, it was not even funny. Some mornings I would come to the office and all the rigs were idle and the room was almost cold...