There are approximately 50,000 battery electric cars currently on German roads as well as roughly 40,000 plug-in hybrid electric vehicles. These hybrids combine a conventional internal combustion engine with a battery. They are often regarded rather critically by environmental organizations and political decision-makers because they are viewed as not “real” electric cars and are supposed to have a poorer environmental record. Up to now, however, there has been no systematic empirical comparison of the electrical vehicle kilometers of battery electric vs. hybrid electric vehicles.

Scientists from the Fraunhofer Institute for Systems and Innovation Research ISI and the Karlsruhe Institute of Technology KIT have now worked together to close this research gap: They compared the performance of 49,000 battery vehicles and 73,000 plug-in hybrids in Germany and the US. The data are taken from fleet trials and automobile manufacturers as well as websites used by drivers to manage and monitor their own vehicles.

Analyzing the data shows: Plug-in hybrids with a real-world electrical range of about 60 kilometers drive the same number of kilometers electrically as battery electric vehicles, namely up to 15,000 kilometers each year. Their CO₂ reduction potential is therefore just as large as battery electric cars. This means that plug-in hybrids are a good addition to battery electric vehicles in order to lower greenhouse gas emissions. This is particularly valid if they are charged using electricity generated from renewable energy sources. The study shows that their carbon balance is even better if it is taken into account that fewer CO₂ emissions are released during the production of plug-in hybrids than during the production of battery electric vehicles due to the much smaller batteries required for the former. In addition, they can foster the diffusion of electric mobility because they do not have a problem with restricted driving range unlike battery electric vehicles.

Dr. Patrick Plötz, who leads the study at Fraunhofer ISI, emphasizes: “Plug-in hybrid vehicles represent a good addition to battery electric cars in order to meet the goal of reducing greenhouse gases. They have often been judged too critically in the past based on insufficient empirical data. However, it is important that they have a sufficiently large battery with a real electrical range of more than 50 kilometers and, in addition, that the decarbonization of the electricity system continues to be advanced.“

According to the study, the decreasing CO₂ emissions during battery production and the increasing diffusion of rapid charging points will shift this advantage more and more in the direction of battery-electric vehicles in the coming years.

The results of the study have now been published as an open access article “CO₂ Mitigation Potential of Plug-in Hybrid Electric Vehicles larger than expected” in the journal “Scientific Reports“. The study was conducted within the framework of the “Profilregion Mobilitätssysteme Karlsruhe” (Profile Region Mobility Systems Karlsruhe). Fraunhofer ISI and regional research partners are pooling their expertise in this think tank to develop efficient, intelligent and integrated mobility solutions. Further information is available at http://www.profilregion-ka.de.

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• Figure: Average electrified annual kilometres for different PHEV (green) and BEV (red) models from the US (squares) and Germany (circles). The shaded areas are sample size weighted local smoothers (95 % confidence bands). © Fraunhofer ISI / Creative Commons Attribution Licence
• Article: CO2 Mitigation Potential of Plug-in Hybrid Electric Vehicles larger than expected (Scientific Reports)