Put simply, the main trouble with electric vehicles is the fact that batteries have far less energy-density by weight than liquid fuel, so much so that to get a 300 mile range in all batteries would require adding a substantial amount of weight, which would significantly impact performance, not to mention price.

However, they have a huge advantage in that electricity charged from the grid is very efficient compared to burning a fuel such as gasoline, since about 2/3rds of the energy of gasoline is wasted between exhaust, and radatior heat. A lot of efficiency is also lost inherently in gasoline engines as they need to be able to operate at widely varying levels of load. A diesel based powerplant can spin a turbine enegine at an optimum RPM, and recapture most of the waste heat as steam power.

Also, by charging at night when there is excess generation capacity, trickle-charged grid electricity is cheap, probobably on the order of 10 times cheaper per mile than burning gasoline.

This is why the plug-in hybrid system is a nice blend. Add just enough batteries to handle most of your shorter trips, without loading on too much weight (still gets most of the cost savings associated with all electric) while using the high-energy-density liquid fuel only when needed for extra power, for longer range, or for when it is inconvenient to charge (road trips, etc).