efficiency of electric cars vs gas? I have been listening to my friends brag about electric cars and I can't seem to convince them that electricity is not some magic force that comes out of the wall outlet.  It must be produced somewhere, in most cases by a coal fired plant, where the chemical energy of hydrocarbons are are transformed to electrical energy by a generator, which is then transmitted hundreds of miles, where it is transformed to ionic energy in a charged battery in a car, which is then converted again into mechanical energy by the engine which turns the tires.  Every time the energy is converted to a different form it loses most of its potential right? Isn't it much more efficient to burn fossil fuels directly at the source - the cars engine? Unless the electrical plant powering the batteries of an electric car is nuclear or hydro, do not electric cars increase total emissions? Anyway, I'm just looking for opinions? am i crazy? 
 A: That's a very interesting question. I have been thinking about calculating the total emission of an electric car and I'm pretty sure that in a country like mine, where 90% of the energy comes from coal, it would exceed emissions from a car power by internal combustion engine. I hope I can find time for that in the near future. If I do, I promise to publish the results here.
Anyway, I found an article on this topic by Ozzie Zehner of University of California, Berkeley. It doesn't say about the exact efficiency, but presents an interesting point of view.
"(..)Another impediment to evaluating electric cars is that it’s difficult to compare the various vehicle-fueling options. It’s relatively easy to calculate the amount of energy required to charge a vehicle’s battery. It isn’t so straightforward, however, to compare a battery that’s been charged by electricity from a natural-gas-fired power plant with one that’s been charged using nuclear power. Natural gas requires burning, it produces CO2, and it often demands environmentally problematic methods to release it from the ground. Nuclear power yields hard-to-store wastes as well as proliferation and fallout risks. There’s no clear-cut way to compare those impacts. Focusing only on greenhouse gases, however important, misses much of the picture.
Manufacturers and marketing agencies exploit the fact that every power source carries its own unique portfolio of side effects to create the terms of discussion that best suit their needs. Electric-car makers like to point out, for instance, that their vehicles can be charged from renewable sources, such as solar energy. Even if that were possible to do on a large scale, manufacturing the vast number of photovoltaic cells required would have venomous side effects. Solar cells contain heavy metals, and their manufacturing releases greenhouse gases such as sulfur hexafluoride, which has 23 000 times as much global warming potential as CO2, according to the Intergovernmental Panel on Climate Change. What’s more, fossil fuels are burned in the extraction of the raw materials needed to make solar cells and wind turbines—and for their fabrication, assembly, and maintenance. The same is true for the redundant backup power plants they require. And even more fossil fuel is burned when all this equipment is decommissioned. Electric-car proponents eagerly embrace renewable energy as a scheme to power their machines, but they conveniently ignore the associated environmental repercussions."
Full article can be found here.
If I can add something, electric cars can be charged from renewable sources only if a distributed generation exist and most of the countries have centralized energy system. So when You plug Your car in, You can't really choose whether it will be charged with renewable or fossil energy.
