General Motors will build a Chevrolet Impala sedan that operates on either gasoline or compressed natural gas (CNG), GM Chairman and CEO Dan Akerson announced at an energy summit. It is the only manufacturer-produced full-size bi-fuel sedan and is expected to go on sale next summer as a 2015 model.

The Chevrolet Impala bi-fuel sedan addresses the range anxiety issue associated with vehicles that run only on natural gas, Akerson said. It features a factory-engineered and fully warranted powertrain that switches from CNG to gasoline. Total range is expected to be up to 500 miles — 150 miles using CNG and 350 miles using gasoline.

Akerson said sales volume is expected to be small, at least initially.

“Most of our customers are going to be commercial and government fleets, and selling 750 to 1,000 units in the first model year will be a home run,” he said.

This is because the infrastructure for CNG fueling stations is not yet fully developed, with only 1,200 publicly available CNG stations nationwide. The bi-fuel option will appeal to those traveling out of the range of a CNG fueling station and will allay range anxiety.

Natural gas is a cleaner-burning transportation fuel compared to petroleum products and costs significantly less than gasoline at current prices. CNG vehicles typically have 20% fewer greenhouse gas emissions than gasoline-powered cars, according to the California Air Resources Board.