Originally Posted by donrapello
Yeah.. I tried that psu calc also and it gives me recommended minimum psu of 950. I've been running just fine with my HX750, 4.8Ghz + Sli OC'd
I'm pretty confident that OP would have no problems with that 850w psu.
I think those PSU calcs do calculate a little on the high side. They probably try to account for things like how long an average user might use the PSU (they do degrade over time), and they probably also try to err on the side of caution to make sure you definitely
don't buy a PSU that's going to be too weak. If they told you that your rig is going to pull 650W and that's exactly how much it does pull, a lot of people would then buy an exactly 650W PSU and have it fail after a year (or not work at all from the start). My guess is that they are estimating high to give you solid advice rather than recommending the bare minimum. They probably also try to account for a margin of error, plus the fact that a lot of PSUs are rated in peak wattage rather than continuous. Just a hunch though.