Source: http://www.afdc.energy.gov/locator/stations/  (as of May 2013), http://nhts.ornl.gov/tables09/ae/work/Job27748.html 
The transportation sector is the source of more than a quarter of total U.S. greenhouse gas emissions. One way to reduce these emissions is to increase the number of electric cars (as long as the cars use relatively low-carbon electricity). But policymakers, car makers and sellers, and consumers all need a better idea of where an electric car, and the infrastructure needed to accommodate it, can best meet consumers’ needs.
In the map above, C2ES put together two sets of data to show places where driving patterns would indicate that most trips could be powered entirely on the battery power of an all-electric, plug-in hybrid or extended range electric car.
One of the map’s layers shows the concentration of charging stations throughout the country in green (the darker the green, the more charging stations). The U.S. Department of Energy’s Alternative Fuels Data Center  provides a nationwide database of publicly available electric vehicle charging stations. The number of charging stations is one indicator of a geographic area’s electric car “readiness.”
The map’s other layer shows the distance traveled for 85 percent or more total trips taken by all drivers in a metropolitan area. You can click on any of the regions to see the share of trips that are less than 10, 20, and 30 miles. Note that this information is not based on drivers’ average trip length, but on an estimate of total trips by all drivers. The Federal Highway Administration’s National Household Travel Survey  provides information on the length of trips for all travelers by metropolitan statistical area , which is a geographic region with a high degree of social and economic integration. (Not all metropolitan statistical areas were covered in the survey.)
The mileage chosen (10, 20, and 30 miles) corresponds well to the plug-in hybrid or extended range electric cars on the market today. The Chevy Volt has an electric range of more than 30 miles, the Ford C-MAX Energi has an electric range of about 20 miles, and the Toyota Prius Plug-in has about a 10-mile electric range. Each of these vehicles also has a gasoline engine for longer trips. Importantly, every all-electric car available today offers more than 30 miles of range.
There are a number of takeaways from this map. First, every all-electric car on the market today can accommodate more than 85 percent of all trips in all of these regions, as can the extended range electric Chevy Volt. This information might help ease consumers’ “range anxiety” about driving an all-electric vehicle (the fear of running out of juice). It also means Volt drivers can electrify most of their trips while still enjoying the benefits of having a gasoline engine available whenever they need it. Second, most charging stations are concentrated in densely populated areas with a notable exception around New Orleans, which also happens to be the only metropolitan statistical area surveyed where 85 percent or more trips are less than 10 miles.
The data from the National Household Travel Survey indicates Americans in our most populated areas could electrify trips without moving to fully electric vehicles. If the share of electric trips can approach 100 percent, it becomes much easier for drivers to find an alternative solution for other trips, making a transition to all electric vehicles more likely. One of the keys is how drivers handle their other trips. Will they rely on gasoline in their extended range or plug-in hybrid cars, mass transit, a private bus, or another conventional car? It’s also very important to consider the miles traveled powered by different fuel types in order to measure greenhouse gas emissions and oil use in the aggregate. Electric trips, however, are a great way to look at the transition to alternative fuel vehicles without replacing conventional technology outright.