I think you are missing the big picture. Yes the li-cobalt format requires a bit more energy for temp control, BUT it's lighter that any lithium tech out there right now.
In the end what matters is total wall to wheel usage, which the roadster is very comparable with the rav4 ev, and the Leaf. Yes the roadster is lighter, but that is really irrelevant as it also has more that twice the range, and doesn't get penelized as much in cold climates due to the already present temp controls.
What is going to be very interesting is Teslas Model S efficiency, and wall to wheel numbers, both in hot and cold climates as it's a heavy car.