Chevrolet Volt

When it comes to the country's two most popular plug-in vehicles, a premium-gas-powered security blanket can make the difference of about four all-electric miles a day. That's the crux of the US Department of Energy's EV Project Vehicle Summary Report for the second quarter of 2013 on how drivers use the Chevy Volt (PDF) and Nissan Leaf (PDF).

In a nutshell, Volt drivers put on about 760 all-electric miles a month (or about three-quarters of their total, the rest being powered by the car's on-board gas-powered generator), while drivers of the all-electric Leaf put on about 630 miles a month. So despite the fact that the Volt's electric range is about half of the Leaf's 76-mile single-charge range, Volt drivers actually drove about 20 percent more miles on electrons. The average Volt driver went 41 miles per day when the vehicle was driven (74.6 percent of that, 30.5 miles, on battery power) while the average Leaf driver went 29.5 miles.

As noted by Green Car Reports, there could be many reasons for this discrepancy. It may be a case of self-selecting vehicle purchases, where drivers who commute longer distances are more likely to buy a Volt over a Leaf. Or maybe Volt drivers, with their limited EV range, top off whenever possible and thus end up with more EV miles (they did have 1.5 charge events per day when the car was driven, compared to 1.1 for the Leaf). Or maybe something else. In any case, with each model moving about 18,000 units in the US during the first 10 months of the year, such findings are sure to spur further discussion about which drivetrain technology has more legs.