Phoronix have reported a major power regression with the kernel that Natty uses. It appears that the regression started with the Maverick kernel but has dramatically worsened with Natty.
There is a high priority LaunchPad bug report - the release notes have been updated, the fix has been committed but not yet published for 11.04, though it is fixed in 11.10.
Phoronix have been doing various regression tests.
One test suite has revealed that for many users, adding pcie_aspm=force into their grub increases battery life.
A recent article presents further possible boot options applicable only to intel users. Using all four extra boot options up-to 27% power saving is reported. However there are possible downsides:
"i915.i915_enable_rc6=1 - RC6 was enabled by default for a while, but then it ended up being too buggy for some hardware configuration so it had to be disabled. For affected systems on the current code-base, enabling RC6 can cause GPU hangs. The Intel RC6 feature allows the GPU to enter a lower power state when the GPU is idling.
i915.i915_enable_fbc=1 - This kernel option enables FBC (frame-buffer compression) for the Intel graphics driver. Frame-buffer compression is not enabled by default since for some systems when frame-buffer compression is active there is a bug where the screen is not being properly repainted when using a compositing window manager. As implied by the name, frame-buffer compression will compress the buffer of what's to be drawn to the screen so that less memory bandwidth is used on screen refreshes, and as a result, less memory being confused.
i915.lvds_downclock=1 - This kernel option will down-clock the LVDS refresh rate, which can increase power savings as a result. However, for systems that do not properly support LVDS down-clocking, the screen can begin to flicker during use."
Note - use these extra kernel options with care - for my laptop, i915.i915_enable_fbc=1 stopped Unity-3D from working.
Use these instructions on how to modify your grub.
