Refer: http://www.makeuseof.com/tag/easily-increase-battery-life-tlp-linux/
Ubuntu
In Ubuntu, you’ll want to do the following:
$ sudo add-apt-repository ppa:linrunner/tlp.
$ sudo apt-get update
$ sudo apt-get install tlp tlp-rdw
If you are on a ThinkPad, you’ll need to install a few more packages for maximum battery life, which you can do with the command sudo apt-get install tp-smapi-dkms acpi-call-tools.
# Start the service, only needs done once, will start automatically on boot-up
$ sudo tlp start