These are the stats from the US Dept of Energy for the year 2000. Where the electricity comes from:

Based on primary energy source, coal-fired capacity represented 43 percent of the Nation's existing capacity. Gas-fired capacity accounted for 19 percent, nuclear 14 percent, renewable energy sources 12 percent, petroleum 7 percent and pumped storage hydroelectric.

Most of that energy to charge up your electric car still has to be pulled from the ground in the form of coal or oil.

The renewable sources need to be built up ( solar, wind ) then maybe electrics will be more efficient.