[quotemsg=10649957,0,421409]What does the Sandy Bridge CPU clock down to in order to help put this into perspective?[/quotemsg]
SB and IB both clock down to 1.6GHz, so clocking down to 800MHz is essentially going down to 1/2 of the idle clock. If paired with even lower voltages at 800MHz then it would mean massive power savings for 'always on' equipment.
I use my rig as both a gaming/production rig, as well as the home file server. Because of it's file server uses my machine is not ever allowed to go to sleep. Sandy Bridge is not a huge power hog, but my next upgrade should be to Skylake or Skymont in ~3-4 years, and the idle power on that should be essentially nothing.
The bigger issue for power use on computers is the GPU. My wife's last upgrade went from a Core2Duo with a 8600GT to an Ivy Bridge i3 with HD4000 graphics. Sure, the CPU takes less than 1/2 of the power at idle, but dropping the GPU made for massive gains in power consumption. Even my own rig went from a 9800GT to a GTX570 which has a pretty big drop in idle power consumption, but moving to a chip just 1 gen later would cut that in half again.