Parallels as a root cause?
I need to run Parallels in Coherence mode constantly as a basic function of my job, and my late-model MBP (MacBookPro8,3 / i7 / 2.2 GHz) lately has been constantly running at nearly 0% battery power, even though I almost never use it unplugged. I haven't had any sudden power losses, but it's horribly frustrating to have my entire system slow down periodically when I have the relatively unusual high-CPU process I need to do. Generally speaking, I'm not under a large load of any sort doing anything very involved, although I do tend to have quite a few programs running (but inactive in the background). I just got back from a 3 1/2 hour lunch meeting during which my machine was on the screen saver and I had nothing happening on it during my meeting. Straight upon returning to work, it had 2% battery power and the fans are cooking like mad... looking at the Activity Monitor, I saw that my JIRA client (a java app AFAIK) was using 400% CPU and whatever else... while it wasn't doing anything? This isn't the rule, that may have been an anomaly, but still this issue has been happening to me pretty constantly over the last month or so whereas previously I don't recall ever having to deal with it at all!
My coworker who shares the same basic sort of usage pattern (we're both web developers) has also had a lot of issues with his machine just not charging or barely charging over a long period of time when it's plugged in, and he says that almost always he can "fix" the issue by simply suspending the Parallels VM and starting it back up again. My mileage has varied with that solution, but overall it does seem really bizarre and is horribly frustrating to constantly be battling the power supply issue with a machine that is essentially just a desktop replacement and is plugged in 95% of the time.
