Max, if you bought a Tesla say, and had heard about range anxiety, you would throw the glossy sales blurb brochure away, you would charge it then, given your driving style and other factors, drive it until (not in one session) you hit the equivalent of the fuel warning light came on then, make a note of the real world distance, that is a far more important than a figure in a hand book but yes, there is a bit of faff involved in this process 