Not sure about other car makers. But I find this pretty accurate +/- 5% in Tesla
When navigating to a destination,Model 3helps you anticipate your charging needs by calculating the amount of energy that remains when you reach your destination. When navigating, the map displays this calculation next to the Battery icon on the turn-by-turn direction list (seeNavigating to a Destination). When the turn-by-turn direction list is compressed, touch the top of the list to expand it.
The calculation that predicts how much energy you will use is an estimate based on driving style (predicted speed, etc.) and environmental factors (elevation changes, wind speed and direction, ambient and forecasted temperatures, air density and humidity, etc.). As you drive,Model 3continuously learns how much energy it uses, improving accuracy over time.Model 3predicts energy usage based on the driving style of the individual vehicle. For example, if you drive aggressively for a period of time, future range predictions will assume higher consumption. Some factors that contribute to predicted energy (such as forecasted temperatures and wind speed) are available only whenModel 3has internet connectivity.
To determine if you have enough energy for a round trip, touch the Battery icon on the turn-by-turn direction list to display an estimated calculation of your round trip energy usage.
https://www.tesla.com/ownersmanual/model3/en_eu/GUID-01F1A582-99D1-4933-B5FB-B2F0203FFE6F.html#:~:text=Predicting%20Energy%20Usage,-When%20navigating%20to&text=The%20calculation%20that%20predicts%20how,and%20humidity%2C%20etc.).
