The decrease would be so unbelievably small that it would not make a difference.
The truth is that every intel chip has what is called a VID and this varys from chip to chip and it is the voltage required to operate the chip. Usually higher numbered models are binned and will run at higher speeds with a lower VID.
So it is possible that the 2.3Ghz could actually take less power than the 2.2 or whatever.
The amount of power used has very little to do with the rated speed.