How big a PSU do i need to add a second 980ti to my rig?

[BottomsUp]

I have a CorsairTX 650 now. i6700k, a hand full of SSDs, 980ti and thinking of adding a second 980ti.

Thanks

 

[Koween]

Use the http://www.evga.com/power-meter/ calculator. I think the minimum is around 750w, recommended around 850w. Going by just the tdp you would get something around 250w per gpu and 100w for the cpu, so a total of 600w. Now, afaik, the tdp isn't really accurate when it comes to max power consumption, but it's close. Add in the efficiency curve of PSUs (don't want to run the psu at max capacity nor at very low capacity for optimum efficiency) and you get somewhere around 800w.
I used it some time ago when I needed a new psu for a 5820k and a 980ti - I remember thinking "should get a psu that would support 980ti sli" and went with a 850w unit.

 

[Tsumi]

Depends on how far you're going to overclock. If completely stock (including stock processor), you can get away with your current 650 watt PSU. Overclocking with no voltage increases, minimum of 750 watts. Anything beyond that and you want to be in the 850 watt range.

 

[caw2007]

I ran mine with a Corsair HX850 with no problems. They were water cooled MSI Gaming Xs.