With increasing concern over the environment and ever-stringent emissions regulations, the electric vehicle has been investigated as an alternative form of transportation. However, the electric vehicle suffers from relatively short range and long charging times and consequently has not become an acceptable solution to the automotive consumer. The addition of an internal combustion engine to extend the range of the electric vehicle is one method of exploiting the high efficiency and lack of emissions of the electric vehicle while retaining the range and convenient refueling times of a conventional gasoline powered vehicle. The term that describes this type of vehicle is a hybrid electric vehicle. Many configurations of hybrid electric vehicles have been designed and implemented, namely the series, parallel and power-split configurations. This paper describes parallel hybrid electric vehicles that are battery dominant and have the ability to externally recharge from the wall socket. Both component selection and control strategy is discussed. Additionally, a definition of the degree of hybridization, or a description of the relative size of the electric motor to the internal combustion engine is presented. Finally the discussion will illustrate that an increasing degree of hybridization leads to higher overall vehicle efficiency, namely fuel and energy economy.