Viktor's calculation is for a laptop, of course. It look strongly as though it is affected by power saving features on the laptop, to give measurably lower power consumption at lower CPU usage.

Doing the same measurements on a PC without the ability to scale back the processor and manage power so carefully, the normal consumption is higher than the laptop, but the consumption at 100% is only fractionally higher. I think it was Graham who performed this calculation. Anyway, the results are in the forum FAQs. Anyway, the bottom line is that a PC can run at 100% for the same price as 60%. (Or, if there is a difference, then it is negligible. Note that all computers vary, and this may not hold true for everyone.)