I am currently running Ubuntu 18.04 which ships with a
4.15.x series kernel, but as reported around the web the
4.17 series have improved power management and can apparently
extend battery life.
I have been running this latest series for a couple of weeks now and the battery life on my Lenovo laptop is greatly improved, coming very close to or even the same as the battery life I experienced using Windows out of the box.
I've never really needed to upgrade the kernel a particular distro ships with beyond the usual updates, except in this case which I explored due to the abysmal battery life I have always experienced on any of the distributions I have tried.
Though not as common as Debian, which moves at a much slower pace, any time I researched manually upgrading kernels for Ubuntu I've always seen posts and comments generally discouraging it, and I guess depending on how it is done it can be error prone and could potentially lead to a non-bootable system. Although I am quite familiar with a lot of Linux, there are still a lot of things that I don't know and don't necessarily have time to research before hand or fix, especially when I am still needing to get a lot of work done.
The best solution I have found for this is
the official Ubuntu mainline kernel repo
which contains automated builds of the latest supported releases. You can
simply download the necessary .deb files (ensuring you get the
-headers. -image.
-modules components) and just:
# apt install ./linux*.deb