Is there such a thing as a really "green" car?

Nissan have just announced that they will be opening the first mass produced electric car plant in England in 2013.
The way I see it, electricity needs power stations and that still causes pollution and uses up energy. ( apparantly a refill for this car will use up as much electricity as your average home use per day ).
Wheres all this extra electricity going to come from? For myself it just doesnt add up.