Vehicles with plug-in hybrid drives are intended to facilitate the transition to electric mobility. They can cover shorter distances purely on electric power and offer a combustion engine as a backup for longer trips. According to Empa studies funded by the Swiss Federal Office for the Environment (FOEN), the actual proportion of purely electric driving depends heavily on usage—and, in particular, charging behavior. “If someone owns a plug-in hybrid and does not charge the vehicle regularly, that person is effectively driving a heavier vehicle with a combustion engine. Due to the additional weight of the battery and electric motor, consumption can even be higher than with a comparable conventional gasoline engine,” explains study author Miriam Elser.

Vehicle design is also crucial: Vehicle weight, drive design and battery size influence how efficiently a plug-in hybrid performs on the road.