Ford expects its 2012 Focus Electric to become the "first five-passenger electric vehicle with a 100 miles per gallon equivalent (MPGe)." The company will try to promote the magic triple-digit number as a key differentiator compared to the Nissan LEAF. But the Focus Electric's higher $39,995 price tag might be the more important number. Besides, the real-world numbers for driving range between the LEAF and Focus Electric are essentially identical.

Despite its official EPA rating of 32 miles in electric-only mode, the 2012 Fisker Karma plug-in hybrid returned a shocking 51.6 miles in electric-only mode during official efficiency tests conducted in Europe.

Weight is the enemy of fuel economy, and the Karma tops the scales at 5,300 pounds—SUV territory. The best hope for putting the Karma on a diet rests with the battery pack. But Fisker says most drivers will stay within the car's 32-mile electric range, with the equivalent of 52 mpg.

Now that Toyota’s Prius Plug-in Hybrid has been officially announced, we can begin the comparisons with the other plug-in electric vehicle with an extended driving range, the Chevrolet Volt.  The underlying question is which is more important to consumers: electric driving range, or total vehicle fuel efficiency?

Even without the additional hardware, vehicles can make money from the grid simply by speeding or slowing the rates at which the batteries are charged. While not full vehicle-to-grid, EVs can play a role today in ancillary services such as frequency or voltage regulation with the right systems in place.