I drove my Signature Performance to LA on I5 yesterday and decided to take the opportunity to test the actual range of the car at different highway speeds. Here is what I found:
Leg 1, Oakland to Harris Ranch (175 miles): I put cruise control on 55 MPH and because of light traffic, I never had to take it off. Somewhat to my surprise, my average energy consumption was 282 Whr/mi, which equates to almost exactly 300 miles on an 85 Kwh battery (assuming that you can actually pump 85 Kwh into your battery, of course). I had always figured that the 300 mile number was just marketing hype, but guess what? The car can actually get that far, if you happen to be on a 300 mile long flat interstate. At any rate, upon arrival at Harris Ranch I was relieved to see that the single supercharger bay was empty. I did, however find a sign advising me that more charging bays were under construction and would be completed by "March 2013". How are we coming on that, Tesla? Note that, with the exception of Altamont Pass, this leg was essentially flat road. The Grapevine was yet to come.
Leg 2, Harris Ranch to Tejon Ranch (110 miles): On this leg, I set cruise control to 65 MPH and again I never took it off. At this speed, i got 332 Whr/mi, for a range equivalent of 256 miles. Again, the road was almost totally flat. So that extra 10 MPH cost me about 45 miles of range. Moral: If you're getting low on battery, slow down!
Leg 3, Tejon Ranch to Atwater Village (80 miles). Tejon Ranch lies right at the foot of the Tehachapi Mountains, and over the next 15 miles Interstate 5 climbs roughly 4,000 ft. to Tejon Pass. I put cruise control back to 55 and headed uphill. Now, even though the model S has a lightweight aluminum body, it weighs over two tons because of the one ton+ battery. And since a LOT of energy is required to lift two tons 4,000 feet, I was prepared to see some startling numbers. Sure enough, by the time I crested Tejon Pass, my average energy consumption for the leg was totally in the toilet: over 700 Whr/mi. Now, because of regeneration:I knew I would get some of that back on the way down the other side, but I was really amazed to see that by the time we reached Castaic at the north end of the San Fernando Valley, the meter was back down to 285 Whr/mi! In other words, I had recovered essentially all the extra energy required to climb Tejon Pass. The Grapevine turned out to be no problem at all. Oh, by the way, I never touched the brake pedal on the way down.
Note: The model S has a toggle which turns off regeneration, but I have no idea why anyone would ever want to do this -- it just wastes energy and uses up your brake pads for nothing,
Conclusion: The Model S is an amazing car that does essentially everything Tesla says it does.