 The following table shows the overall fuel economy expressed in terms of miles per gallon gasoline equivalent (mpg-e) and the utility factor for the ten MY2014 plug-in hybrids available in the U.S. market, and EPA's best estimate of the tailpipe emissions produced by these PHEVs.In order to account for the upstream emissions associated with the production and distribution of electricity, and since electricity production in the United States varies significantly from region to region, the EPA considered three scenarios/ranges with the low end scenario corresponding to the California powerplant emissions factor, the middle of the range represented by the national average powerplant emissions factor, and the upper end of the range corresponding to the powerplant emissions factor for the Rocky Mountains.The EPA estimates that the electricity GHG emission factors for various regions of the country vary from 346 g /kWh in California to 986 g /kWh in the Rockies, with a national average of 648 g /kWh.