Another thing to consider is that just because someplace has one or more charging stations doesn't mean there won't be someone using it already.
Certainly a consideration. I think the distribution of both vehicles and charging stations is so sporadic right now that there is no way of knowing if you might hit such a wait or not. There are six Tesla stations at the Home Depot that I frequent in Ontario, OR, and I have never once seen anyone using one of them. I could see lines forming someplace like San Francisco, though.
Of course not everyone would have to take the full 20-40 minutes to charge up. There must be some electric drivers that like me, don't like to see things get down to less than half a tank. I assume that would considerably reduce charging time.
