Here are some fixes you can do to improve battery life in elementary os luna. If you notice, Elementary OS Luna is based on Ubuntu 12.04 which has various issues. I don't know why Elementary OS
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Ubuntu vs Windows 8 battery life
I just installed Ubuntu Raring Ringtail on my HP Sleekbook and I am loving it. Battery life went from 2 hours with Windows 8 up to 5.5 while using Ubuntu 13.04 and that's with screen brightness a little