Photo courtesy of Amp.

Photo courtesy of Amp.

The U.S. Environmental Protection Agency (EPA) has approved Amp Electric Vehicle’s Workhorse E-Gen Electric Truck.

The medium-duty truck has a 2.4L, small spark-ignition engine as an emergency generator to charge its battery pack after it reaches a predetermined charge.

The battery pack paired with the on-board backup generator and a transmission-less direct-drive system increases its range.

The new powertrain is expected to bring down operating costs for fleet managers. The E-Gen will deliver 20 mpg compared to the 7.5 mpg operators typically get, said Amp's CEO Steve Burns. The new powertrain for the E-Gen will be available in 2015.