As we increase the voltage supplied to hit higher clock rates, the power consumption of these processors increases beyond the specs set forth by AMD and Intel.
Every CPU is different of course, but we generally noticed higher idle power numbers across the board versus past processor reviews with chips running at stock settings. Of course, you have to be careful in comparing this setup to the one used in my Phenom II X6 1090T story, for example. We’re using twice as much memory, a dual-GPU graphics card, and a much more aggressive processor cooler.
Under load, the Core i7-875K uses the most power, followed fairly closely by the Phenom II X6. Even at 4.66 GHz, the 32 nm Core i5-655K is much easier on the energy bill.