I've had my 2013 Model S for 9 months now and have put 15000 miles on her. About 6000 of those miles were during two long road trips with another coming up in late November. What I have learned is that the charge estimator works really really well except in places where the speed limit on the interstates is 80 mph or more. For the most part the interstate speed limits are posted at 75 mph or less except in the following states. Montana, Nebraska, Nevada, South Dakota, Texas, Utah, and Wyoming. There are large stretches of interstate that are posted at 80 mph or more in all of those states. And if you trust the on board nav you cannot go 80 mph because it will tell you that you have enough energy and you won't. Only 15 or 20 miles after leaving the supercharger you will get the notification that you need to slow down in order to make your destination. I had two ideas as to why this might be happening and I think I know which one it is. Idea one was that the speed limit portion of the mapping database was incorrect and had those sections of interstate set to a lower speed. Idea two was that the calculator code has an over zealous sanity check such that speeds over 70 or 75 mph are treated as if they are incorrect and a more reasonable value is substituted. It occurred to me that it is easy to find out what the nav system thinks the speed limit is. Just get on the interstate and run up to 80 mph and then navigate to the next supercharger. The nav will tell you both the mileage and the time and with that you can calculate what it thinks the speed limit is. I live in Rapid City, SD and the speed limit between Rapid City and the Murdo SD supercharger is 80 mph. This is about 140 miles and about 130 miles of it is posted at 80. I waited until I reached the 80 mph section and punched up the Murdo supercharger and it gave me a driving distance of 131 miles and a travel time of 122 minutes. If you work this out you get a speed of 64.43 mph (60 * (131 miles /122 minutes). And if the energy predictor bases its calculation on you traveling at 65 mph and you go 80 you will fall short. I suspect the sanity check sets the speed to 65 miles per hour when it sees a speed in the map database greater than 70 or 75. This was either done in the Tesla code when the energy calculation takes place or at Google when the speed limit database was generated. After all the max speed limit in California is 65 and if you don't take road trips it would be easy to make the assumption that 80 or more mph would be an impossible number. I am hoping that this is corrected in the about to come out 8.0 software release but I don't expect it. For the right person this would take only a few minutes to correct. Doug Ingraham 2013 Model S 85 Multi-coat Red "The Woman in the Red Dress"