I have an X1 extreme. I’ve never gotten it to last over 2h on Windows. On Linux it can last an hour or so more if I turn off the NVIDIA GPU, but otherwise it’s still abysmal.

Then there’s the stupid BIOS warning that requires you to press ESC for the computer to boot if it’s not plugged in to the official charger, which means that if it ever reboots at night it’ll just keep you awake (because the power management hasn’t been initialized yet so it’s stuck at 100% CPU) until you go press ESC.

Oh and it thermal throttles all the time so the CPU performance is good for a few minutes and then it’s just awful.

The old ones had hot-swappable batteries (a second internal battery - of decent size - kept the device going while you replaced the external one). I used to keep a couple of extra 50 Wh batteries in my backpack and therefore had excellent battery life. The power efficiency wasn't great though.

I now have a Z13 Gen 1 (AMD 6850U) running Fedora and the battery life is passable. It draws 7-8W at idle from a 51 Wh battery.

Cannot properly evaluate now. I never really use it without a cable for too long, and by now the battery must have slightly degraded too. Anyway, it never was Macbook-level, I guess, and it's an oldish model, so you should check actual reviews for current models that you are interested in, there always was plenty of them for ThinkPads (at least, the last time when I looked for a new laptop).

I'll actually answer your question, it's horrible. I have a X1 Carbon and get maybe 3-4 hours on Linux.