Fraunhofer ISI: Plug-in hybrid vehicles are better than their reputation

Scientists from Fraunhofer ISI and KIT (Karlsruhe Institute of Technology) have compared the performance of battery electric and plug-in hybrid electric vehicles in Germany and the US. They discovered that plug-in hybrids with a real-world electrical range of about 60 kilometers drive just as much in electrical mode as battery electric vehicles, and their potential for reducing CO2 is therefore just as large. The results have now been published in the journal “Scientific Reports”.

© Fraunhofer ISI / Creative Commons Attribution Licence
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).

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

The Fraunhofer Institute for Systems and Innovation Research ISI analyzes the origins and impacts of innovations. We research the short- and long-term developments of innovation processes and the impacts of new technologies and services on society. On this basis, we are able to provide our clients from industry, politics and science with recommendations for action and perspectives for key decisions. Our expertise is founded on our scientific competence as well as an interdisciplinary and systemic research approach.

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