Well i have free power so... depends i guess.
Hope your not stealing it....Are you getting solar power? Or you at a college dorm that includes utilities? Or at a company using mining as a way to test hardware?
I'm also interested to know too, I find it so hard to reduce my electricity bills.
Just use your electricity during off peak hours and partial peak hours, that should help. Look at your electric bill for that info. Nothing is free in life.
In my place, only commercial have off peak. For resident its all the same.
In my area of California, we have off peak hours from 9pm to 10am M-F. Weekends, off-peak more of the 2 days except for a part of the afternoon. On peak hours are M-F from 1pm to 7pm, until winter time. Rates in my area are as follows: $0.1323/kwhr Off Peak, $0.153/kwhr Partial Peak and $0.3125/kwhr On Peak....
An R9 280X has been added to the hardware comparison page. With OpenGL, it's either as good as the original 7970s or better. At this point, it seems to be way better than the 7970s. It looks like whatever they changed has fixed the original 7970 issues.
https://litecoin.info/Mining_hardware_comparisonThat's pretty impress at I=13..Wonder what it does at I=18?...Maybe 800~900 kh/s....
I believe I=13 would be the highest point, some card just don't work well in high intensity.
If it's like the HD 7970, it can do I=18, even I=20....But on average, most single GPU cards can do at least I=18...I do I=80 on my 2x HD 5870's and HD 5850...