Cars need energy to move. How that energy is generated, stored, and applied to moving the car,

is what is important.

Organic hydrocarbons have issues, but mostly that they are finite.

An electric car may not be any cleaner than a fuel car, if the source for the

electricity is a coal plant.

Energy density - Wikipedia, the free encyclopedia
The best battery on the list is at 1.8 MJ/Kg, Gasoline is about 46 MJ/Kg.

So a cars petrol tank holds 40 liters that's 1840 MJ of energy of which

Mr Carnot allows us to extract 460 MJ (Aprox 25%).

So 460 MJ divided by 1.8 MJ/Kg= 255 Kg

A car would need to carry 255 Kg of Batteries to equal 40 Kg of petrol.