According to the Bureau of Transportation Statistics the average car in 2006 got 22.4 mpg while the average new 2006 car got 30.2 (http://www.bts.gov/publications/national_transportation_statistics/html/table_04_23.html). Combining that information with the rate of 19.4 lbs CO2/gallon of gas, we find that the average car in 2006 generates .8661 lbs CO2/mile while the average NEW car generates .6424.
According to a joint report by the Department of Energy and the EPA (http://www.eia.doe.gov/cneaf/electricity/page/co2_report/co2report.html#electric), the average carbon dioxide output for electricity generated in the US in 1999 was 1.341 lbs CO2/kWh.
With that information at hand I began to look for efficiency information for electric cars. I was unable to find anything official for lead-acid batteries, the type of batteries used with previously available electric cars (i.e. EV1 which was available in CA from 1996 to 1999). The unconfirmed information I found said that the batteries for the EV1 could hold 18.7 kWh of energy and go for about 75 miles on a charge. That works out to .3344 lbs of CO2 per mile.
The next car I looked at was the Chevy Volt, a car that can run on either full electric, full gas, or in a hybrid mode. The Volt uses next generation Lithium-Ion based batteries and is being rushed to market by GM with a target launch date of sometime in 2010. According to gm-volt.com, the Volt can go 40 miles on full electric using ~8 kWh of electric energy. That works out to approximately .2682 lbs of CO2 per mile for trips under 40 miles.
I found the numbers to be somewhat surprising. The new Volt, when it becomes available, will generate 58% less carbon dioxide than the average new gas-powered car does today. I expected that with our fossil-fuel dependent electric generation grid the reductions would not be as significant.
One thing for the environmentalists to keep in mind, however, is that a gas-powered car would only need to get 72 mpg to equal the carbon dioxide output of Volt in full electric mode. This is achievable with only incremental improvements in gas-electric hybrid technologies (the Prius is rated at 48 mpg today). Also, it is important to keep in mind that this rudimentary analysis fails to take into account the carbon dioxide output of the battery manufacturing and disposal process or the gas production and transportation processes.
For an entertaining look at anti-CO2 environmentalism taken out to its logical conclusion, see this article from Reason: http://www.reason.com/news/show/127418.html
I took this post from HERE: http://ionlyreadthearticles.blogspot.com/2008/08/electricity-vs-gasoline.html