10 million free miles worth of electricity and counting.

As Tesla Motors states:

"Tesla Superchargers have charged over 10 MILLION miles to Model S. Enough to go to the Moon and back 20 times."

Going to the moon and back would be a task better suited to the various rockets/capsules made by SpaceX, so let's instead say that those 10 million Supercharger miles are enough to travel around the world almost 402 times.