How Much CO₂ Do Electric Cars Produce?

Many people hope that we can maintain our easy motoring lifestyle after Peak Oil, while simultaneously going easier on the environment (i.e. having your cake and eating it too) by switching to electric cars.  Not just hybrids that still use fossil fuels, but all-out battery-driven electric vehicles.  The assumptions this hope is based on include the following:

• Electric cars are more energy-efficient than fossil fueled cars.
• The electric grid gets some proportion of its power from sources that don’t emit as much CO₂ as the combustion of oil- i.e.  hydro, wind, solar and nuclear power.

First of all we need to find out how much CO₂ is produced when we generate an “average” kilowatt-hour of electricity.  To do that, we find out how much CO₂ each type of power technology produces, multiply that by the proportion of that technology in the overall American generation mix, and add it all up.

 So an "average" kilowatt-hour results in the generation of  about 607 grams of CO₂ - about 1.3 lb.

Now we need to determine how much electricity it takes to drive an electric car 1 kilometer.  From Wikipedia, a modern electric car requires 0.2 to 0.3 kWh per kilometer.

That's not quite all we need to consider though.  There is about a 10% electrical power losses between the generating plant and the charging station of the car.  We will assume the losses related to battery charging are included in the power budget of 0.2 to 0.3 kWh/km.  So for every kWh we need to run our car, we need to generate 1.1 kWh at the generating plants.

Bringing all this together, driving an electric car with an energy requirement of 0.2kWh/km results in the generation of  0.2*1.1*607=135 grams of CO₂ per kilometer.
By the same methodology, an EV with an energy requirement of 0.3 kWh/km results in the generation of 200 grams of CO₂ per kilometer.

How does this compare to a regular car? Average new European vehicles range from 195 g/km for BMW down to 145 g/km for  Citroen.  The overall average is about 162 g/km.  Modern American passenger cars are on the upper end of this range.  There are energy losses (and associated CO2 releases)  involved in getting the gasoline produced and distributed.  Let's be generous and say 15% of the gross energy in the gasoline is required.  This results in an EROEI ratio of 6.7:1, lower than is usually assumed for gasoline.  This additional 20% raises the CO₂ range for ICE vehicles to 167 to 224 g/km.

167 to 224 g/km or an Internal Combustion Engine vehicle, vs. 135 to 200 g/km for a pure Electric Vehicle: it's not an encouraging comparison.  Given the imprecision of the underlying data they can be viewed as essentially equal.

What conclusions can we draw from this calculation and comparison?

The main one is that simply switching to electric cars in most places in the United States at this time won't help save the planet from global warming.

But it's not all bad news.  If the electrical grid evolves to include higher proportions of  wind power, tidal power and possibly more nuclear, the CO₂ advantage of electric cars will improve.  And of course as Peak Oil looms over the horizon in the next few years, there will be distinct cost and mobility advantages to driving electric.  There is a caveat, though.  Regarding the impact of Peak Oil, one of the most commonly voiced concerns is that as oil supply declines we may turn to more coal-fired electricity.  If that happens, driving an electric car recharged from the grid becomes much less attractive..