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For those new to EV's you will no doubt come across discussions about range. Many of those discussions center around the range estimate the car displays and why it does not always match what the rated range is by the EPA (found on the Monroney "sticker" when you but the car). This is probably the most controversial topic concerning EV's and has been the subject of many heated conversations. Here is what you need to know:
1) Range estimates are not a measurement of battery degradation or health despite several third party apps making that claim.
2) Tesla cars have very sophisticated software and electronics that tell the user and or Tesla if something is wrong with the car like problems with the main battery. The software cannot predict everything each and every time (12V batteries sometimes die spontaneously and this happens to all cars on occasion, not just EV's).
3) The range estimate the car gives you is just an estimate and does not take into account all factors like elevation changes, temperatures, winds, etc. Some of the factors can be anticipated using trip planners but things change in real time so remember it is just an estimate. If you change the display to percentage of battery left instead of miles or Km it becomes much simpler and is like a gas car showing 1/2 a tank or 1/4 tank etc. left. You simply fill up when the "tank" is low.
4) Outside temperatures that affects the battery temperature is one of the larger environmental factors that reduces the range so plan accordingly. There are many rules of thumb on "winter" range but they vary since winter in coastal CA is much different than winter in Chicago. Do your homework to set your expectations on range under varying conditions.
5: The EPA range is range measured under laboratory conditions. One of the larger user controlled factors that affects range is driving speed. If you drive fast your range goes down, if you drive slow your range goes up, this is true for all cars, gas or electric.
6: Make life simple and change the range display to percentage of battery left and charge when the battery gets low, it is that simple.