The 2014 Chevrolet Volt remains one of the most fuel-efficient cars sold in the U.S. today. Data aggregated from Volt drivers shows that roughly two-thirds of all mileage covered in done using battery energy from charging with grid electricity. When its range extender switches on, the Volt is rated at 37 mpg combined--high for a compact car.
With its 38-mile electric range (as rated by the EPA), Volts that travel less than that distance daily may go for weeks without switching on their gasoline range extenders. And as GM will tell you, repeatedly, just about four out of five U.S. vehicles cover less than 40 miles a day. In fact, Volts have a function built in to ask permission to switch on their gasoline engines every few months, to circulate liquids and keep the system in good running order.
The Chevy Volt is rated at 98 MPGe, a metric that measures how far a car can travel electrically on the amount of energy that's contained in 1 gallon of gasoline. That puts it in the middle of the plug-in pack for efficiency these days. Several vehicles now exceed that number, including Chevy's own Spark EV battery-electric minicar at 199 MPGe, but many of them are far smaller and offer less performance than the Volt.
We continue to rate any vehicle that plugs in and can operate on grid power alone for some distance as a 10 on our Green scale. Battery electric cars would rank higher than any car with a gasoline engine, but the Volt can still be driven with no tailpipe emissions at all for lengthy distances. It all depends on how much the driver exceeds 35 to 40 miles a day, assuming overnight recharges. The highest-mileage drivers may burn less gasoline in a 50-mpg Prius than in a Volt running on relatively little grid power and then at 37 mpg thereafter.
Recharging a Volt battery pack takes 7 to 10 hours using the standard 110-Volt charging cable provided with the car. Level 2 charging stations, which operate at 240 Volts, cut that time in half--but only about half of all Volt owners have one installed at their homes. It's simply not necessary for a Volt used in daily commuting--unlike a battery electric car, for which overnight recharging at 110 Volt may not be enough to replenish the pack fully.
Electricity is virtually always cheaper per mile than gasoline, though its price is far more variable (from 3 to 25 cents per kilowatt-hour) across the country. And as for the "running on coal" assertion, many studies have calculated the environmental impact of driving on electricity produced from dirty coal. A Volt may do marginally worse than a 50-mpg Prius hybrid in a handful of the very dirtiest states. But against an average 25-mpg car, driving a Volt recharged on grid electricity--or any other plug-in car--is always cleaner.