The second annual National Plug In Day has passed, and it marked an exciting milestone: over 200 million oil-free electric miles traveled in the U.S. This translates into 96.5 million pounds of carbon pollution that have not been spewed into the air (even taking into account emissions from electricity to charge EVs). It also means that consumers have avoided purchase of nearly 7.4 million gallons of gasoline and saved nearly $19.5 million dollars in fueling costs (comparing gasoline to electricity fueling costs).
Our 200 million electric miles driven estimate is based on data we compiled on electric miles traveled by the Chevy Volt, and the Nissan Leaf, and Tesla Roadster models, as well as estimates on electric miles traveled by other recent plug-in vehicles, electric vehicle conversions, electric delivery fleets, and factory made electric vehicles prior to 2010 models. (See more on how we got to 200 million miles below.) From there, we determined the approximate avoided gallons of gasoline purchased, the money saved by fueling with electricity, and the pounds of carbon emissions prevented in comparison to a new compact car averaging 27 MPG.
How did we do this? First, let’s look at avoided gallons of gasoline purchased.
How much carbon emissions would have resulted from those gallons? Each gallon of gasoline releases about 25 pounds of carbon pollution taking into account the approximately 19 pounds of carbon emissions per gallon from the burning of gasoline and is emitted from the vehicle tailpipe as well as the approximately 6 pounds of carbon emissions per gallon from the upstream emissions that are a result of the oil extraction, refining, and transport processes.
7,407,407.407 gallons X 25 pounds of carbon = 185,185,185.2 pounds of carbon
We’re not done with this number yet. Next, we’ll calculate the pollution associated with charging EVs and subtract that from the above to get carbon pollution avoided.
Because different parts of the United States have cleaner or dirtier grids, and because EVs are purchased and driven disproportionately in states with cleaner sources of electricity (like California), we wanted to make sure to count EVs, electric miles, and the emissions associated with EV charging based on where people are actually purchasing EVs. The Center for Automotive Research (CAR) report (pdf) for example, estimated that California EV sales would account for 24 percent of EV total EV sales in US in 2012. So, we assumed that 24 percent of the 200 million electric miles were driven in California, and we determined emissions estimates accordingly.
For emissions, we look at the miles per gallon equivalent (MPGe) that a plug-in vehicle has in that state, as the Union of Concerned Scientists shared in their “State of Charge” report (pdf).