I don't know if this has already been posted:
http://www.stanford.edu/group/greend...slaReading.pdf
Even in this (obviously biased, imo) study, the most efficient production EV is roughly double the efficiency of the most efficient ICE cars (well-to-wheel). Considering the Tesla (according to the numbers on their website) should have an mpge of roughly 184. That makes it nearly 84% more efficient than the Nissan Leaf.
So 100% more efficient than a 50 mpg ICE car, and 84% more efficient than the Nissan Leaf. That means, when you actually compare the efficiency of one of the few affordable electric cars to the more efficient ICE cars in "well-to-wheel" efficiency, the difference is not great. Probably less than the difference that could be gained by improving driving habits or having the worst offenders (SUVs, trucks, etc.) replaced by higher efficiency cars when possible.
Suffice to say this is an interesting topic. I am just upset by the fact that so many of the parties involved in doing research are biased or trying to make a point. Unfortunately, the vast majority fall into the category of end-user, so their first concern is for themselves. If they see a personal improvement in economy/efficiency, they couldn't care less about the greater impact.