ECOtality recently published data from its ongoing evaluation of 6,000-plus plug-in vehicle owners. The EV drivers are participants in The EV Project , a multi-year project designed to evaluate charging patterns.
According to ECOtality, the operator of The EV Project, owners of the Chevy Volt  try at all costs to avoid using gasoline. In other words, Volt owners charge not only at home, but also at work or at other public charging sites throughout the day.
Drivers of the Nissan LEAF  charged at home 89 percent of the time—plugging in 1.1 times a day, whereas the average Volt owner plugs in nearly 1.5 times per day. The data indicates that Volt drivers plug in when away from home 21 percent of the time, as opposed to the LEAF owners away-from-home charging of only 11 percent.
This is partly explained by the fact that the LEAF's battery pack stores enough energy for 80 or more miles of driving. On the other hand, the battery pack on the Chevy Volt provides about 35 to 40 miles of all-electric driving, before a gas engine is engaged to extend driving range by a few hundred miles.
"We never anticipated that a 40-mile-electric-range plug-in hybrid would charge more than a 100-percent electric car," said Colin Read, ECOtality’s vice president for corporate development. "You have that gas engine that you’re paying an extra premium for a reason."
These findings indicate that owners of plug-in hybrids could be more frequent users of public charging than previously expected. Those PHEV drivers are likely to want to top up (in quicker charging events) throughout the day, where as owners of pure EVs are more likely to charge up overnight at home—taking off with plenty of juice to last the entire day. The number of plug-in hybrid sales is expected to be significantly larger—as much as double—the size of the market for pure electric vehicles.