Tesla promises coast-to-coast driving in its electric cars

The Tesla Model S fell short of a perfect score in our testing for one simple reason: You can't jump in it any time you want, and drive to absolutely any point on the map at a moment's notice. But, Tesla has just announced a big step in addressing that problem.

To that end, the electric-car startup automaker has announced it will triple the size of its network of Supercharger stations from currently eight to 27 by mid summer. By 2015 it will build enough of the electric car filling stations to allow Tesla drivers to drive cross-country. (Read about our experience rapid charging at a Tesla EV "Supercharge" station.)

Tesla's Superchargers will pump about 160 miles worth of electricity into the cars' batteries in a half hour. Many Superchargers will be placed at Interstate rest areas, where travelers can take advantage of Internet connections, food, and restrooms while their cars charge. While quite the convenience, a 20-minute stop is not the same as a three-minute gasoline fill up.

Read: The Tesla Model S is our top-scoring car.