How Green Is My Electric Vehicle?

Pretty Darn Green! While there are no tailpipe emissions at all, the electricity used to charge the vehicles batteries includes power supplied by fossil-fuel-burning power plants. A precise comparison between electric-powered and gasoline-powered cars is a fairly complicated undertaking. For one thing, the greenhouse gas emissions for the electricity used to power your vehicle depends heavily on when and where you charge your vehicle. If you charge your vehicle at night, or in an area with lots of non-emitting power sources such as hydro-electric, your carbon emissions will be much lower than if you charge your vehicle when inefficient fossil-fuel powered generators supply much of the electricity on the grid.

The table above is our imprecise attempt to compare the emissions of the Miles ZX40S to some gasoline-powered cars. The comparison is based on EPA fuel economy estimates. If you drive in highly congested areas, such as the urban areas of Greater Boston, you're probably using much more fuel and emitting much more pollution per mile than is indicated by the EPA estimates. This is because you are spending, as you might have noticed, a fair amount of time stopped, getting zero miles per gallon. One of the great advantages of an electric drive vehicle is that does not idle. If you are not moving, the motor uses no energy and has no corresponding carbon emissions.

Note: CO2e is pounds of carbon dioxide equivalent. City mpg is according to EPA estimates except for the Miles ZX40S which is estimated by Electric City Cars LLC. Greenhouse gas emissions for the power grids are based on US Dept. of Energy estimates published in 2002 and may not accurately reflect the current greenhouse gas emisions per MWh for the power grids. If electric vehicles are charged at night, CO2e emissions per 1000 miles are likely to be substantially less than indicated in this analysis.

Electric cars will get greener as the electric power grid gets cleaner. All the New England states have established ambitious targets for increasing the amount of renewable energy in the mix of power sources on the grid. And forthcoming federal laws on climate change and renewable energy are likely to force even further reductions in the amount of greenhouse gas emissions per kilowatt of electric power on the grid. This means your electric vehicle will get cleaner as time goes on, whereas fossil fuel powered vehicles tend to get dirtier over time as engine parts wear and lose efficiency.

In combination with bicycles and public transit, electric cars are the best path to sharply reducing greenhouse gas (GHG) emissions from personal transportation. One recent study estimated that GHG emissions from transportation will have to be reduced by 88% to achieve a stable level of 450 ppm CO2 by 2050. The only engine technologies that offer that level of reduction in GHG emissions are battery or fuel-cell powered electric vehicles in which the electricity to charge the battery or the hydrogen for the fuel cell is derived from power sources with little or no GHG emissions.

The sooner our society moves to electric and fuel-cell powered vehicles, the better. Manufacturers need to move up the learning curve to produce better and less expensive vehicles. Drivers need to move up the learning curve to understand the benefits and limitations of the new technologies. City, state, and federal government agencies need to develop the regulations and amenities that accommodate electric vehicles.

Buying an electric vehicle now puts you at the crest of the next wave of personal transportation.