vertexx :
The difference in "Active Idle" power consumption between the FX-6350 and I3-3225 based systems is not quite 20 Watts. That's "Active" idle. I'm sure if you leave your system on 24x7, you'll be in various power saving states less than that.
Except stock AMD CPUs are nowhere near Intel stock performance in moderately threaded applications and once you overclock AMD CPUs to match, AMD's power efficiency drops off the cliff.
As for idle, I repeated multiple times that the $100+/year saving is mostly for people who DON'T IDLE much. In my case, once all my junk is loaded, my CPU rarely gets a chance to drop below 50% load so it spends most of its cores spend their limited idle time in C1 state with the CPU clock pegged at 3.4GHz.