Can the Operating System you have installed on your laptop affect battery life?
Most people would answer "no" to this question. And for the most part, I did too. That is until I experimented a little. For this experiment, I used a brand new 13" MacBook Air with a 1.3 GHz dual-core Intel Core i5 processor, 4 GB RAM and a 128 GB SSD.
I began by testing battery life under Mac OS X Mountain Lion. It’s important to know that apart from ensuring that OS X Mountain Lion was current, I installed nothing more than what was installed on the system. It was tested as-in, out of the box. I copied an MP4 video file to the system, played it in an infinite loop, left WiFi on (connected to my WiFi network, but not really sending much traffic) and set the screen brightness to about 65%. Once the system was ready and fully charged, I unplugged the power cord. 10 hours and 32 minutes later, the battery was dead. Impressive.
For the Windows test, I used the exact same hardware, only booted to Windows 7 instead of OS X Mountain Lion. Again, I updated the OS, but installed nothing else. I copied the same video file and made the same settings changes (WiFi and screen brightness). 6 hours and 33 minutes later, the battery was dead.
So, using the exact same hardware and very similar configurations (as close as you can get when using two different OSes), the battery life is clearly different:
Microsoft Windows 7: 6:33
Mac OS X Mountain Lion: 10:32
Can your OS affect battery life? Absolutely! And in some cases, in a big way. I would be interested to see how Linux would compare in this experiment, using the same settings and same hardware.