[ubuntu] Decreased battery duration

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http://ubuntuforums.org – I have recently returned to Ubuntu after using windows XP. One thing I have noticed is that my battery life has drastically decreased from about 3 hours (on windows XP) to slightly less than one hour (on Ubuntu 12.04) on a charged battery. I have of course kept in mind that the brightness and the type of program I run might affect the battery duration but even with reduced brightness Ubuntu lasts way longer. My questions now are: - How could I improve battery life duration keeping Ubuntu 12.04 ? - Which Ubuntu based Linux OS is the lightest when it comes to battery usage ? (Hardware)