Ubuntu uses more power but you have options, you could decrease the power usage or for save more battery power.
One option is jupiter, this program allows you to change the performace mode in the laptop and you could use 3 performace modes to saving battery.
To install it is very simple, is just:
sudo add-apt-repository ppa:webupd8team/jupiter
sudo apt-get update
sudo apt-get install jupiter
If you own Asus EeePC netbook, also install jupiter-support-eee - required for SHE (Super Hybrid Engine):
sudo apt-get install jupiter-support-eee
This si the source www.webupd8.org