I'm very specific about the time my laptop battery can last as it is very important to me. Will my laptop's battery last longer with Windows 8 or Windows 7, both in similar power plans, considering factors such that Aero is disabled in Windows 8 and many others?
There have been some comparison in the battery life between Windows 8 and Windows 7. Very early tests in the preview showed no improvement, but the latest benchmarks appear to show slight improvement.
You should be aware that battery life will depend on your actual hardware, drivers used, and settings (screen brightness, etc).
The programs installed will also be a factor, for example, the following shows how it can change:
Note: the above comparisons are based on specific hardware, and the setup used for the tests may differ from yours