MotorTrend did another test, this time from Las Vegas, and managed to get a range of 285 miles!
http://www.motortrend.com/features/travel/1209_tesla_model_s_las_vegas/
This was with the A/C on for some of the trip (set to 72F [22C] on a 102F [38C] day!) and the windows down for the rest. I think they could've easily kept the A/C on the entire time if they had set the temperature to something more reasonable like 77-79F (~25-26C).
http://www.motortrend.com/features/travel/1209_tesla_model_s_las_vegas/
This was with the A/C on for some of the trip (set to 72F [22C] on a 102F [38C] day!) and the windows down for the rest. I think they could've easily kept the A/C on the entire time if they had set the temperature to something more reasonable like 77-79F (~25-26C).