Check out the new EVGA PSU Academy page. This page has more information about EVGA Powersupplies, and can be a handy guide when selecting your next PSU unit 
 
http://www.evga.com/articles/00722/academy.asp
 

 
Awesome guide.         

Great Guide.

Real nice guide.  Lots of good info there...

Nice work this is a great write up.  

well it is missing how you figure out what size PS you need. 650watt and up supports 2 way SLI. So if I'm doing 2 980s in SLI I can use a 650W?

Great guide!  Thanks for that...

well, I am no expert on mining.
But my understanding is that you are predominately using the GPU.
 
So, while you might be maxing out both cards at one time (say in excess of 400 watts in this case...more than SLI...(because it is very difficult to use both cards 100% due to the sharing involved in sli) you will not be maxing out the rest of the system at the same time.  When mining the CPU load will be very low...correct?
 
even so, 750 watts should be plenty even if you use the cpu.
 
One caveat:
 
I have not seen mining results with Maxwell. I do not know if the optimizations of Maxwell translate into the continuous loads of mining...AMD cards were optimal for litecoin even though they were beat by FERMI in many other benchmarks...
Just saying: make sure you read up on the type of mining you are doing, if MAXWELL architecture is optimal. ;)
 

However with mining you do not run in sli, you run one thread per gpu and you will max them both out.
 
Yes, that is what I was saying when I mentioned that the SLI wattage would be a lower number. Sorry for the confusion.
 
An alternate approach to reading the reviews, is to buy a $20 kill-o-watt meter.
With your OC, you might be pushing 220-240 watts when mining.
Since you have a card, and a rig, it is very simple to figure out.
 
Just be sure to figure the difference between AC and DC load based on your PSU efficiency.
 
For example, if when mining with one card on your rig you show 320 watts AC, and you are running an older bronze PSU...multiply by .85 to get the DC load. 320x.85 = 272 watts DC load
Do the same for your idle load and subtract and you determine how much mining on a card is required.
Say you show 85 watts web browsing idle...85x.85=72 watts DC
 
So in this case adding a second card would require an additional 200 watts DC.
Anyway, if you are mining...a 750 watt is plenty for the two cards. ;)
Say for the sake of argument 500 watts for the two cards...even with a good 650 watt, that leaves you 150 watts for the rig...on the high side for a modern intel rig under light load. :)
Now if you had a high CPU OC and wanted to fold on the CPU at the same time...things would be tighter for sure.
 
EDIT:
The g2 1000 watt is a Plat unit that EVGA sells as gold because it was just on the line.
So you could get 92% rather than 90% efficiency.
While on sale with rebates, it is still $50 more than the 750 sale price
http://www.newegg.com/Product/Product.aspx?Item=N82E16817438010
 
You would save about $12 a year in electric cost if you were mining 24/7/365
so, a four year payback for the additional $50 ;)
 
 
 
 

http://extreme.outervision.com/psucalculatorlite.jsp

 
Nice read. Thanks.