This is a question received by Intel Software Network Support, along with the response supplied by one of our experts at Intel:
Q. Is power consumpition higher if CPU utilization is higher?
A. Yes, with an increase in CPU usage, you go to higher processor frequency states (P-States), which draw more voltage and hence power is higher as well when running in balanced/adaptive mode.
You need to consider multiple factors when analyzing this. If you are talking about a workload that can finish as fast as possible (e.g. a fixed data set like MP3 encoding), even if the CPU load is higher it's better to run as fast as possible and then go idle, instead of running for a longer period of time at a lower P-State.
If you are asking about a fixed time application, such as DVD playback or MP3 playback, then yes, reducing CPU usage will help save power. The key point is to let the OS and GVIII control the P-States and do not change the operating frequency from within the applications.
Some further reading that may help you: