I am back from my Atlanta - Charolotte trip. The trip was 250 miles from my house to the supercharger in Charlotte. We charged the car on the max trip setting and got about 259 rated miles. On the way there, I drove on average around 65 mph with the Climate OFF the majority of the way. It was raining just about the whole way there. I made it with 5 miles to spare but I never 'fell behind' in terms of how many miles I had left to drive and how many 'rated miles' I had..
On the return trip, it only rained about a quarter of the way and we averaged about 70mph. We had the Climate OFF about one third of the time. We made it home with 2 miles left. What was very useful was seeing the Projected Miles (I think by pressing the Energy icon) and whenever the Rated Miles was about the same or less than the miles left to our destination, I switched off the Climate and slowed to around 55-60 mph. The impact of doing this on the Projected miles was pretty drastic so that when we had 50 miles left to go and we had 51 rated miles, I knew we were in good shape because I could slow down and gain a few extra miles if I needed to.
The GPS kept insisting that we deviate from our route and get the car charged at a third party charger. Purplewalt, thanks for your post. Glad I attempted to make it on a single charge even tho I caused the wife a few anxiety attacks. Interestingly I met someone at the Charlotte supercharger who had decided not to chance it and was going to charge his car on the way in Greenville. Bottom line: Tesla needs to add a supercharger in Greenville. So many folks take trips on the 85 and for there to be so few superchargers is a head scratcher.