A study is made of several outstanding issues concerning the commercial development of environmental control systems for electric vehicles (EVs). Engineering design constraints such as federal regulations and consumer requirements are first identified. Next, heating and cooling loads in a sample automobile are calculated using a computer model available from the literature. The heating and cooling loads are then used as a basis for estimating the electrical consumption that is to be expected for heat pumps installed in EVs. The heat pump performance is evaluated using an automobile heat pump computer model which has been developed recently at Oak Ridge National Laboratory (ORNL). The heat pump design used as input to the model consists of typical finned-tube heat exchangers and a hermetic compressor driven by a variable-speed brushless dc motor. The simulations suggest that to attain reasonable system efficiencies, the interior heat exchangers that are currently installed as automobile air conditioning will need to be enlarged. Regarding the thermal envelope of the automobile itself, calculations are made which show that considerable energy savings will result if steps are taken to reduce 'hot soak' temperatures and if the outdoor air ventilation rate is well controlled. When these changes are made, heating and cooling should consume less than 10 % of the total stored electrical energy for steady driving in most U.S. climates. However, this reslt depends strongly upon the type of driving: the fraction of total power for heating and cooling ('range penalty') increases sharply for driving scenarios having low average propulsion power, such as stop-and-go driving.