I have a few rigs left over from the scrypt and other alt coin mining days that I keep simply for playing around with and recently switched over to mining Eth. Currently I have 6 AMD 7970 GPU's running and I make roughly 1 Eth per day from each of them, or 6 Eth daily total when pointing to a pool. I should also point out this include present pool bonuses that are being offered so in the future this will go down somewhat with both increased competition and removal of bonuses. I am probably currently mining 5.2 Eth per day and get ~.8 bonus.
So in my situation, and already having the equipment (meaning no initial investment to pay back) I get the following:
6 x 7970 GPU's running at ~200 watt draw each (from wall including overhead of CPU/MB): 1,200 watts/hr
My electricity is fairly high in my area at $0.13 kw/h, so I have: 1.2 kw/h x $0.13 x 24 hours = $3.75/day (rounded up) in power costs.
Eth has been selling for between $0.80 - $1.60 in the past month, lets use $1.20 average: 6 Eth /day * $1.20 = $7.20
So on average, for the past month or two I have been not quite doubling my money $7.20 income - $3.75 power = $3.45/day profit.
It is winter here, so I do get a bit of benefit from the extra heat which I do not take into consideration in my calculations, but as you can see if I didn't already have the equipment it would not be worth the investment in hardware. Of course Eth could go up in price, but often the hash rates catch up to keep the profits from mining minimal, so you would be better off just buying them and speculating on price appreciation if that is your goal.
I will keep at it until the break even price goes below 0, as I look at it currently as getting half priced Ethereum, but again this is from more the hobbyist perspective than someone trying to make any money off of it.
What are the frequency and voltage of your cards? Your electricity is cheaper compared to those in some western Europe.
Core clock 1025 / memory 1375 voltage is slightly undervolted from the scrypt mining days. I tried playing around with the settings when I first started mining Ethereum but didn't really see any appreciable difference in hashrate. I haven't tried lowering voltage much more, as they were tweaked before to run scrypt without crashing if I went much lower and the power draw right now is not too bad. Each card had its own sweet-spot on voltage so it was a pain to dial in each one (thus my hesitation to do it again) but most were just a bit under stock anyway.
Yeah, I am sure I am not at the highest electricity rates in the world, but I also know there are plenty of people who pay half what I do, and in some countries I have seen as low as 2-3 cents per KWh. Since it is winter, I do get the extra benefit of the heat being put to a good purpose.
I will also add that with the recent price hike, my Eth per day has declined to about 5 Eth per day, down from the 6 that I was earning previously. Of course with Eth now selling at $2.50 each, my gross daily income from mining is 5 x $2.50 or $12.50/day, so with power rates staying constant my net income has increased to around $8.75 a day. Still not enough to consider buying more cards, but at least it is the most profitable GPU coin we have had in some time.
