Current electricity sources. Approximately 50% of all electricity sold in the United States comes from burning coal.  Coal is cheap, but is also the dirtiest fuel (highest carbon content).  Charging EV batteries from the grid will frequently produce the same or even more greenhouse gases and other air pollutants than running a conventional gasoline car in many parts of the country. The National Research Council released a report in 2009 (Figure S-3) showing that the health costs of running a battery electric vehicle are greater than the health costs of a regular gasoline vehicle, a hybrid electric vehicle and a plug-in hybrid.  This same NRC report showed (Figure S-4) that the greenhouse gas emissions from a battery EV are greater than the GHGs from a gasoline hybrid electric vehicle.

For the purposes of this model, however, we have assumed a utility generating plant composition based on the West Coast grid mix, which has only 32% electricity from coal instead of the US average of 48% coal.  Thus the results presented here are more favorable to plug-in hybrids and battery EVs than the US as a whole.

Greening of the grid. In addition, we have assumed that the grid becomes “greener” over time:

• Renewable energy (wind, solar, geothermal, etc.) increases over time
• Nuclear energy increases slightly over time
• Coal plants are either replaced with units that have carbon capture and storage (CCS) capability, or older plants are retrofitted with CCS; all non-CCS coal plants are phased out by 2070:

The area in this graph labeled “PHEV Off-Peak” indicates the electricity that is generated at night using then-current excess nighttime generating capacity.  No new generators are required to produce this electricity. The crosshatched area at the top of the graph indicates new electricity demand for some daytime PHEV charging that will require new generation capacity. This is based on an EPRI (Electric Power Research Institute) PHEV charging profile.  Thus PHEV and BEV advocates state that some car owners will need to be able to charge their car batteries at work during the day to entice them to purchase those electric vehicles.  But this daytime charging will often correspond to the peak utility load, so new generation capacity must be added to accommodate daytime PHEV and BEV charging.