PowerTOP reports that the majority of wakeups are being caused by
[kernel scheduler], and
What are these, and can I do anything to reduce the number of wakeups they are causing?
Seems to be normal... at least last time when I tried to hunt down this problem I read somewhere the exact explanation... And as far as I can remember it was not a problem.
Tough you can find a documentation here: Ubuntu help
Also you could run powertop as sudo and look for the C-States. If they are in idle at lowest it should be ok.