Extended range electric vehicles (EREVs) are similar to plug-in hybrids except the internal combustion engine (ICE) is not designed to power the drivetrain on its own. EREVs are designed to travel at all speeds in electric mode. Interest in EREVs is gradually increasing.
Chevrolet Volt. The Chevrolet Volt allows for 35 miles of gas-free driving, after that the onboard 1.4L gasoline engine starts up to turn a generator to replenish the battery. It also uses regenerative braking. It has been acknowledged by GM, the maker of the Volt, that the gas engine at high speeds (when the batteries are depleted) can help power the wheels when the electric drive motor is spinning too fast to be efficient. This has caused a debate as to classify the Volt as an EREV (according to Chevrolet) or as a PHEV (as classified by the EPA).