While I'm on the subject. . . I did my own analysis based on my own needs for the car. The longest trip I make on a semi-regular basis is from my home to Waco Texas and back. It's 68 miles, a pretty good road, there are no big hills to climb. Assuming I have no good opportunity to charge up in Waco. . . That's a 136 mile round trip. I have to add a comfortable margin to that, so I can drive around town, possibly take some short side trips, or drive a little faster maybe. So I arbitrarily added 20 miles to my requirement. Now I need a 156 mile range to make this trip with confidence.
The battery pack degrades with time and usage, and we can assume it's due for replacement when it gets to 80% of the original capacity. With a range of 200 miles when new, that would be down to about 160 miles before the end of its service life. So. . . Even as the battery ages and degrades, it should still just about handle my trip to Waco and back -- but we're starting to cut it close. If the range were reduced any further, I would have to start reconsidering my options.
Fortunately, I don't think it's going below 200 miles. Tesla seem very confident that they can promise 200 EPA highway miles "or better". According to the letter:
We continue to drive engineering improvements to increase range, and explore options that would allow you to choose between increased range and enhanced performance. There are still some unknowns and variables that will become known as we develop and test our VP cars, so we have chosen to communicate a floor of 200 miles and strive for upward revisions in the future.
Also, some have noted that when the ESS comes due for replacement, it will be surprising if the new ones don't bring in better technology and longer ranges. So for buyers this may only be a temporary setback.