Deal is when an electric car with 150-200 miles of range is cheaper than a gasoline powered car, then for the vast majority of people the next car purchase will be electric or a plug in hybrid (twice the mileage of conventional). Assume 12,000 miles a year for a mix of cars

    %   Type             mpg  gal/yr       ext
    50% Electric         --   0            0
    25% Plug in Hybrid   80   150 X 0.25 = 37.5
    25% Non-Hybrid       30   400 X 0.25 = 100
    -----------------------------------------
    Total                                  137.5

    100% Non-Hybrid      30   400 X 1.00 = 400
    ------------------------------------------
    100%                                   400

So the mix of electric, plug in hybrid and gasoline results in a 2/3 reduction in gasoline consumption.

And that's in the US. In countries without domestic oil production the choice will be made for you.