A car that emits absolutely no pollution is great, right? What if you think about it like this:

More than 50% of electricity in the U.S. is generated from coal. Power plants are a major source of air pollution, with coal-fired power plants spewing 59% of total U.S. sulfur dioxide pollution and 18% of total nitrous oxides every year. Coal-fired power plants are also the largest polluter of toxic mercury pollution, largest contributor of hazardous air toxics, and release about 50% of particle pollution. Additionally, power plants release over 40% of total U.S. carbon dioxide emissions, a prime contributor to global warming. Power plants are second only to automobiles as the greatest source of NOx emissions. Coal-fired power plants are also the largest single source of sulfur dioxide (SO2), releasing about 2/3 of the total SO2 pollution each year.
The electrical generation from the coal power plant is 33% efficient

The power transmission from the plant to the users home/business is 92.8% efficient.

The charging efficency of the battery is between 71% and 91% depending on the rate of charge.

The effeciency of the electric motor is between 90% and 95%.

That puts the total efficiency at 19.6-26.5%. Not much better than a standard vehicle, right? Now take into account the tons of extra power that goes into the production of these huge batteries, as explained by Curtis73 here http://www.automotiveforums.com/vbulletin/showthread.php?t=750719.


Sources:
http://www.sierraclub.org/cleanair/factsheets/power.asp
http://www.unc.edu/~jrhester/policycoal.html
http://en.wikipedia.org/wiki/Electric_power_transmission
http://www.buchmann.ca/Chap4-page4.asp
http://www1.eere.energy.gov/industry/bestpractices/pdfs/mc-0382.pdf