I've had my Model S since August, and am still having a bit of trouble getting a sense of how much energy I'm using. With my old Volt, it was easy: at the end of a trip, you could see miles used, estimated miles left. If I drove 25 miles and had an estimated 10 miles left, that's about 35 miles compared to the EPA estimate of 38: I did slightly better than the EPA average. With the Tesla, things get trickier. It doesn't show estimated miles left (just EPA miles left or ideal miles left, which are really just different ways of displaying % of battery left), and the battery is so much bigger that for shorter drives the math isn't as accurate. Issue 1: The EPA for an 85kW Model S shows 370-380Wh/mi (.37-.38 kWh/100mi), and a 265 mile range. Those numbers do not compute. 85kW divided by 265 miles is 320Wh/mi. The EPA shows a range 15% lower than what it should be -- is that because it either  assumes people charge to 85%,  15% of the battery is "hidden" when charged to 100% (not used. or  something else? Issue 2: Here's what I saw today: I drove 14.9 miles, used 5.1kW, at 341kWh/mi. I used 18 rated miles (going from 199 to 181 rated miles, which could really be ~17.1 to 18.9 rated miles). So according to the display, I used about 20% more than the EPA estimate (I used 18 rated miles worth of electricity, but only actually drove 14.9 miles: 18/14.9=1.2). But that suggests the EPA is 284Wh/mi. So I'm seeing three different EPA values (~284Wh/mi, 320Wh/mi, 370-380Wh/mi), and am lost. Any ideas?