The “long tailpipe” theory argues that electric vehicles do not really
create zero emissions, because the electricity needed to charge the batteries is produced in power plants. In June 2001, the Argonne National Laboratory released a US Department of Energy-sponsored study that found that battery-powered electric vehicles result in a 35% reduction in greenhouse gases.  This reduction was based upon electricity generation from the national grid, roughly half of which is derived from coal and roughly 30% of which is derived from clean, renewable sources like nuclear, solar, wind, biomass and hydroelectric power.  In 2004, an analysis of data from a California Air Resources Board staff report on greenhouse gas emissions from motor vehicles found that electric vehicles resulted in a 67% reduction in overall greenhouse gases in California, compared to a car powered exclusively by gasoline, and were nearly twice as effective in reducing greenhouse gas emissions than a hydrogen fuel-cell vehicle.  California’s energy grid is considerably cleaner than the national grid, with roughly 20% of the state’s electricity being generated via coal-fired plants. 
Finally, some energy experts and utility analysts contend that millions of plug-in hybrid electric vehicles could be added to California’s fleet without substantially impacting the state’s current energy grid, since most of the charging for the plug-in hybrid electric vehicles could be done during off-peak hours, at night.  . It’s estimated that 5,000 plug-in hybrids charging at night would represent less than 0.1 % of peak electrical demand in the state.  Moreover, they would also have strong beneficial environmental impact, since a plug-in hybrid vehicle that gets its energy from the grid during off-peak hours is thought to produce one-third the carbon dioxide emissions of an exclusively gas-powered car with a fuel efficiency of 24 mpg.  Tim Lippman of UC Berkeley’s Institute of Transportation Studies also points out that not only is our state and national grid becoming cleaner with increased use of renewable energy sources, but also that it is much easier to control emissions from a relatively small number of power plants than millions of tailpipes, each being a point of emissions and harmful, respiratory pollutants. Lippman also notes that emissions modeling research shows that when it comes to the concentration of harmful pollutants emitted from burning fossil fuels, height matters; the closer to the ground the emissions are, the more they tend to concentrate, making emissions from tailpipes at ground-level potentially more damaging than those from a coal-fired plant’s smokestack, which may be 200 ft. or more of the ground.