I read a lot of comments from people who think that electric cars are necessary to save the world: they cost nearly nothing to operate, and they produce no pollution. These people have little understanding of the technology involved. They see the GM advertisements that say the Volt gets 230 mpg, and think that oil companies have kept this technology away from us for years. The 230 mpg claim is spurious at best because the car does use energy. Here is an article that addresses this issue. Electric cars use energy just as gasoline powered cars do. Gasoline cars have an average efficiency of about 20% based on the energy capacity of the fuel. An electric car has an efficiency of perhaps 80% when based on the energy stored in the car's battery. But, the electricity in the battery came from an electric generation system that has an efficiency of 25% from the fuel burned to the plug n the house. Thus the overall efficiency of the electric powered car is no better (0.8 times 0.25 equals 0.20) than a gasoline powered car. Since much electricity is produced by burning coal, and coal produces a lot more CO2 than gasoline, there is no environmental gain for electric powered cars. Of course environmentalists see some future time when all electricity is produced by wind mills and solar cells, but that is far in the future, if ever. Cost comparisons are somewhat more difficult to make since gasoline has a road tax attached, and electric power does not. (When all cars are electric, some other type of road tax will be necessary, such as a system in which all cars have a GPS, and people are taxed on the number of miles driven.) Electric car manufacturers claim that their cars get about 4 miles/kw-h, which translates into 853 BTU/mile. If I assume that these cars are similar to a gasoline powered model that gets 30 miles per gallon, that translates to 3833 BTU/mile. (If I compare the energy actually delivered to the wheels, the electric car is at 853 X 0.8 = 682 BTU/mile and the gasoline car is at 3833 X 0.2 = 777 BTU/mile. So, to be consistent, I need to adjust the mileage for the gasoline powered car to 34 mpg.) Now to compare cost, I use the price of gasoline without taxes. At present prices of 12.5 cents/kw-h and gasoline at $2.10 per gallon, the electric car costs $0.03125 per mile to operate, and the gasoline powered car costs $0.06176 per mile to operate (ignoring road taxes). But, the battery powered car costs at least $10,000 more than the gasoline powered car. And after about 6 years the battery is expended and has no residual value. If I assume the cars are driven 15,000 miles per year, then, including 6 % interest on the money, the battery adds $ 0.151 per mile to the operating cost of the electric car. If a person drives 10,000 miles per year, the additional cost is $ 0.2267 per mile. Thus an electric car is not cost effective. Now consider a compressed natural gas (CNG) car. It would require about 3.4 standard cubic feet per mile. At a price of $8/mcf (which is more than the current spot price of less than $3/mcf), that translates to an operating cost of $ 0.0272 per mile (again with no road tax). Even considering a much higher price for NG than the current spot price, the CNG car is cheaper to operate than either an electric car or a gasoline powered car. Estimates I have seen indicate that a CNG car would cost $500 to $1000 more than an electric powered car. One difference between the CNG car and the battery powered car is that the CNG car has residual value after 6 years, and in fact the CNG fueled engine will last longer than the gasoline engine. But, if I use an additional cost of $1000, the 6 year life and the 15,000 miles per year used in the electric car comparison, the additional operating cost for the CNG fueled car will be $ 0.015 per mile. Thus, the CNG fueled car is more economical to operate than a gasoline fueled car or a battery powered car. Another idea from this analysis is that people who do not drive many miles per year might be better off to stick with a gasoline (or more economically, a diesel) fueled car. Another thing to consider is that the cost of fuel is a minor part of the cost of ownership. If I assume a car costs $30,000 and has a life of 10 years, it costs $3000 per year. Interest at 6% adds $1800 per year. Insurance and maintenance adds $2000 per year. If a person drives 15000 miles per year, the ownership cost is $ 0.453 per mile. If a person drives 10000 miles per year, the cost of ownership is $ 0.68 per mile. Thus, the fuel cost (at $0.02 to $0.06 per mile) is a small fraction of the total cost of ownership, no matter what fuel is used.