Curious about this too. In my Model S and X rentals I really liked watching the graph that showed what % battery level I would arrive at the next Supercharger with. I don't know if that same screen is available on the 3 or not. Please let me know how to bring it up if such a creature exists.
Right now there is no consumption graph or energy app like on the S/X but on the navigation screen you can see at what %battery level you'll reach your destination and how long you have to charge at Superchargers if you need them to reach your destination
The closest thing I've seen is the thin bar right below the battery/range that moves left to right depending on acceleration/regen. It shows instantaneous power input/output, but AFAIK there is no "Energy" screen like in the S/X