Somewhere on the Internet, the other day -- I didn't keep track of where -- I stumbled onto some people talking about how electric cars shouldn't be encouraged in areas were burning coal was a principal source of electric power, suggesting that in such a situation, CO2 emissions could actually increase. And they were so matter-of-fact about it that I had to wonder -- did they have a point? So, I did a little research and a few calculations.
My i-MiEV's "tank" is 16 kWh, on which I can travel about 64 miles. According to the U.S. Energy Information Administration
, burning coal yields a little over 2 pounds of CO2 per kWh -- call it 32 for a "tank", or 0.5 lbs CO2/mile.
With my old Prius, although the EPA rating was 50 mpg, I needed longer trips to achieve that -- with my usual driving pattern, what I got was more like the mid-30's. Call it 32 mpg for simplicity. So, 2 gallons to cover 64 miles. The EIA says
that burning a gallon of gasoline yields almost 20 pounds of CO2 -- so, 40 for the 64-mile trip, or 0.625 lbs CO2/mile.
So, the electric car is already ahead (quibbles with my rounding aside)... but it gets better. In practice, most electricity comes from a mix of sources
. In my case, the overall mix of sources used by the electric company yield slightly less than a pound of CO2 per kWh -- less than half the pure fossil fuel CO2 yield.
This analysis doesn't take into account the costs of extraction, refinement, etc., but AFAICT, adding in those costs would only make the gasoline side of the comparison look worse.