What they'd rather not tell you is that it can take 12 hours to charge the car as opposed to the 30 seconds it takes to refill a fuel tank.
Some electric cars have a quick-charge feature, but if it's used too much, the batteries will need to be replaced in as little as 5 years. The max you can get out of them is about 10 years. Since these batteries are more expensive than a conventional engine, these cars aren't exactly cost effective.
Even with free electricity.