Lots of cars get 45 MPG and they get better acceleration. Unfortunately they in their majority are sold in Europe and they ran on diesel. But you can find cars getting 40 here.

You all unfortunately did not get my point. I based my calculation on 20% fuel saving - which is an average for hybrids. But thats not the point. Even if it was 40% (which is not) we are still talking abou 500 MW (less then one block in a powerplant)