I'm not sure if this is a bug or not. If I put my Mac in "sleep" mode with a full battery and Parallels is open. The next morning (8 hours later) my battery is down to 20% and activity monitors shows that Parallels has used 50% of my battery while the system was in sleepstate, the other energy hog was activity monitor itself.. I would expect that if the Mac is put to sleep: Parallels should completely power down.