Power usage should scale approximately with application utilization.
However...
Just as an example, my last electric bill said the price per thousand watt hours was 3.125 cents, even at full utilization from the lowest power to the highest power chips you said was only 60 watts difference.
There are 8,760 hours in a year. So even if your PC was on 24 hour as day the whole time at max utilization, you would save you 16 dollars a year... not even worth considering, especially considering you don't know the rest of the systems power utilization which is going to be very different from just the processor. I wouldn't even look at the wattage used when buying a chip, with one caveat.. That wattage is almost entirely lost as heat, heat is bad for electronics.