Energy density is the "elephant in the room" that determines a lot about electric vs. internal combustion. The Tesla S uses a 100 kWh battery that weighs 1,375 lbs. 100 kWh is approximately the same energy contained in 2.1 gallons of AvGas. So, you have a 2 gallon capacity (about 13 lbs.) in a 1,375 lb. container. Makes perfect sense to me. NOT!

And we aren't even bringing up the environmental impact of producing the battery and then disposing of it when its life is used up.