The U.S. Energy Department has updated its national eGallon price, which is a way to compare the costs of fueling electric vehicles with the cost of gasoline.

The DOE said the price of fueling an electric vehicle rose to $1.18 per eGallon on July 19, up from $1.14 from earlier in the year.

The DOE noted that plug-in electric vehicle (PEV) sales tripled from 17,000 in 2011 to 52,000 in 2012.

Also, during the first half of 2013, U.S. buyers purchased more than 40,000 PEVs.