That's a big "+" on your figure - it's about 300 Watt-hours per mile, or 3600W constantly, if you're going 60 mph. For comparison, one horsepower is about 750 watts - a Tesla is a very low-drag car.
Anandtech reported [1] that the TDP of the whole board is around 250W. The Tegra SoCs are probably around 10W, but that doesn't get you much in the way of GPU horsepower.
1: http://www.anandtech.com/show/9903/nvidia-announces-drive-px...