Under normal conditions, I use 350 Wh/mi (watt-hours per mile). This is 17% more than "rated range" because -- and this is a technical term -- I drive like a madman.
However, when driving to Tahoe (7000 feet higher), I end up using 850 Wh/mi: over 2x higher electricity consumption, because mountains.
All this talk of tires and wind resistance is a red herring for topography, which does more to limit/extend range than any other factor.
What's more, this could be so easily addressed with software: when I input my destination into GPS, the car should tell me my expected range. It knows the topography. Use the force, car!
Taken one step further, since Tesla is constantly transmitting telemetry to home base, Tesla HQ likely knows the average battery consumption of all other drivers who have ever driven that route. This would allow non-topographical variables (traffic lights, potholes, road conditions) to be factored into the range calculation as well.
Edit: Mistakenly used kWh/mi instead of Wh/mi units. Hat tip to Tarrosion for the correction.