Increased emphasis on reducing vehicle emissions has led San Diego Gas & Electric Company to develop a hybrid electric vehicle powered by a natural gas fueled engine. This vehicle employs a downsized internal combustion engine driving an alternator for average power needs, and a small battery pack to provide additional power for acceleration, and to store energy during regenerative braking. The vehicle is driven by advanced, high efficiency, brushless DC motors through a fixed gear reduction transmission.Keeping up with the ever changing California emission requirements is an important part of San Diego Gas & Electric's (SDG&E) business, touching all aspects of company operation. To reduce emissions in its vehicle fleet, SDG&E has instituted a program of converting certain vehicles to compressed natural gas (CNG) fuel to act as a “pathfinder” for other fleet vehicle operators in its service territory as anticipated tighter emission controls on California fleet vehicles are enacted. In parallel with the CNG conversion program, the Research, Development and Demonstration (RD&D) Department of SDG&E is developing a prototype natural gas powered hybrid vehicle which offers the potential for even lower emissions than current CNG conversions. The hybrid vehicle concept is a spinoff from all-electric vehicles which are performance and range limited by current battery technology, and is based around replacing over 50% of the electric vehicle's battery pack with a small, light weight, engine driven electric power supply.