Cost Equivalent MPG and CO2 for Electric Cars


Cost Equivalent MPG

Electric cars are coming.  The first mass produced electric car, the Chevy Volt, is due out later this month, with handful of other electric vehicles expected to be released next year.  One issue concerning electric cars that has been hotly debated recently is what should electric cars list for fuel efficiency - miles per gallon (MPG)?  Since electric cars can run entirely on a battery powered by electricity, it is debatable what MPG, if any, the EPA should attribute to these vehicles.  It has been argued that they Volt be given an MPG rating of anywhere from 32 to 230.

Here at, we think there is a better way for drivers to compare the MPG of these cars - by cost.  Since traditional MPG doesn't fit with electric vehicles, we have come up with a new metric, cost equivalent MPG.  Cost equivalent MPG converts electrical energy usage of electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) to its equivalent in gasoline based on cost.  For example, if gas price is $2.50/gallon, an electric car that could go 100 miles on $2.50 worth of electricity would have cost equivalent MPG of 100.

Due to the nature of the calculation, cost equivalent MPG for any given electric car is subject to change along with changes in the price of electric power and/or gasoline.  For PHEVs, such as the Volt, cost equivalent MPG will also depend on individual driving habits (i.e how much driving takes place on the gas powered backup engine.)

Drivers may easily calculate their personalized cost equivalent MPG with our new and improved Electric Car Calculator.  Simply select the state you live in, enter your driving habits and choose two cars to compare to determine your personalized cost equivalent MPG along with other useful data.

CO2 Emissions

Here at, we also want to make sure that actual CO2 emissions for electric cars is being properly accounted for.  The recent fuel economy labels (pdf) proposed by the EPA and NHTSA do not take into account CO2 emissions from electricity generation and delivery.  Our electric car calculator will determine total CO2 emissions, taking into account both tailpipe CO2 (from burning gas) and upstream CO2 (from electricity generation).   The calculator will also take into consideration the driver's state and the source(s) of electric power generation of that state since this can significantly affect CO2 emissions.

For more information, see our Cost Equivalent MPG FAQ and the press release.

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