Comment by rootnod3

Sorry, thought I had posted, but didn't get through. It's a T480 with the 72Wh and the 24Wh battery running on FreeBSD. Screen has also been replaced with a low power usage screen which helps a lot in saving battery while still giving good brightness.

Most of the time I am running StumpWM with Emacs on one workspace and Nyxt in another. So just browsing and coding mostly.

OpenBSD gets close, but FreeBSD got a slight edge battery wise. To be fair, that is on an old CPU that still has homogenous cores. More modern CPUs can probably benefit from a more heterogenous scheduler.