I've not tried it personally, but I've read good things regarding Ubuntu's battery life on phones compared with Android. My understanding is that a lot of it is

I've not tried it personally, but I've read good things regarding Ubuntu's battery life on phones compared with Android. My understanding is that a lot of it is down to background apps being paused, like in iOS. I think the tablet mode would do the same, while the desktop mode won't, but in that cause you could probably plug in.