I've been tracking this thread for a while with interest. A week or so ago I drove to Schruns, Austria and back, which gave me a good opportunity to explore the subject of long range driving more thoroughly. I have a pilot's background, so beforehand I developed a trip calculation spreadsheet that would let me forecast not only leg time and energy consumption but also (supercharger) charge time and thus total leg & trip time. I took the approach that it's not really possible to predict the rate of consumption (Whr/km) with speed, so instead I just worked out a rate budget per leg. In other words my driving plan was to calculate an average power consumption per leg and then drive at whatever speed would give that rate.
For charging I assumed the given figure of 80% charge in 40 mins, 100% in 75 mins and built that 'curve' into the charge calculation. Obviously there are various estimates involved, so when we did the trip I viewed the estimates as being in need of practical confirmation and was conservative. During the trip I logged the various parameters for each leg in the spreadsheet or, when I forgot, I used VisibleTesla to recover the data later.
The result is in a spreadsheet that you can find here:
https://dl.dropboxusercontent.com/u/56093827/Tesla Trip Calc & Log.xlsx
There are some interesting results of this 'experiment':
1) On this basis it's perfectly possible to fairly accurately predict energy use, range and charge time. Given that one can't forecast actual energy consumption due to the effects of weather, speed, terrain, etc, a "rate of consumption" budget works well. Simply put, if your rate is higher than the spreadsheet figure then you either need to slow down or think about an intermediate charge. To me this is a great relief - I now have absolutely no concerns about long range driving using the superchargers.
2) By playing with the spreadsheet I discovered that it's way better to travel faster and charge longer: sprint from supercharger to supercharger and charge for a few minutes more.
3) It's a little better to arrive with as little range remaining as sensible, as charging an empty battery goes faster than charging a full(er) one. But the difference is not huge.
Further, I found that by focussing on average energy consumption during a leg, as shown on the "Trip" display, on this route I could pretty much drive along at 130-140 kph, where that's allowed. Note that the effect of traffic and speed restricted zones means that my outbound average speed was 99 kph (30 mins delay due to traffic) outbound and 106 kph return. On the other hand there were plenty of sections where we were driving at 150+.
Note that it's possible to plug an sensitivity analysis into the figures and see how travel time varies with average speed and average rate of consumption. I've left that out to keep the sheet 'cleaner' for now.
Overall I booked an average consumption of 231 Whr/km outbound and 238 Whr/km on the return trip without having to modify my driving style at all. This included a couple of 190+ sprints! Outbound times: 8:36 driving plus 2:16 charging for 837 km. Return times: 7:51 driving and 2:36 charging. The difference in charge time is probably because when I left home I had 384 km range typical. When I left Schruns had only 284 km range.
All in all a very interesting and reassuring exercise.