I am battling with the absurd power usage of ubuntu 11.04. On windows 7 (which came preinstalled) I can get around 4:30 hours turning everything off (wifi, bluetooth, lowest brightness for screen) with same settings I get 2 hours with ubuntu. I was wondering if I install xubuntu will that help me reduce my power usage?
Yes, but not on that scale.
To change your kernel to something that will increase your batter life, you need to use the kernel that is in the Proposed updates repository. For more on how to enable that, look here.