Lenovo’s battery life numbers are consistent generation to generation, but wildly unrealistic. My 2015 thinkpad (since replaced by m1 air) was rated as 12 hours but could do at most half in practice doing very light tasks and typically ran about 4 hours. So when you buy a thinkpad you should assume actual battery life is a third to half of the rated life.
Apple’s numbers are equally unrealistic. They rate my m1 air for 15 hours, but in practice it gets to around 8 hours.
Eh... I have a T480. It's advertised at "17+" hours. With the 72Wh extended battery fitted, it has a total of 96Wh energy storage. With some small effort tuning (making sure the nvidia GPU is properly powered down etc) I can easily get its consumption down to about 5W - less, with lowered screen brightness and wifi off. 96Wh / 5W = 19h 12 min. Seems legit.
Apple’s numbers are equally unrealistic. They rate my m1 air for 15 hours, but in practice it gets to around 8 hours.