In my experience Linux is quite an energy hog. The best combination I could find is to use Debian with vey low screen brightness. For some reason Debian seems more efficient than other distros I tried, but it's just my impression, nothing I measured. I also installed powertop
. When I run on battery and I want to squeeze the most out of it I just disable everything from powertop, then put all files I will work with on my SD card and the rest in a ramdisk. That way the HD will stop spinning too. I also turn off the wi-fi switch.
All of those things also apply to Sabayon, so you might have a try. Anyways, it all depends on what you're going to use.
I recall a colleague telling me about this new technology on mac books that allowed the OS to automatically switch from the main graphic card to the integrated chip when the gpu wasn't needed. Apparently this saves a lot of power, but I don't think anything other than apple computers can do that.