Plug-in hybrid electric vehicles (PHEVs) are consuming up to three times more fuel in real-world driving conditions than manufacturers claim, according to a comprehensive analysis of nearly one million vehicles conducted by the Fraunhofer Institute. The study, released Wednesday, casts doubt on the environmental benefits often associated with PHEVs and is prompting calls for stricter regulatory oversight.
The Fraunhofer Institute’s research, which examined PHEVs produced between 2021 and 2023, utilized data wirelessly transmitted by the vehicles while in operation. This allowed analysts to determine actual fuel consumption, contrasting it with the figures reported through EU-approved certification processes. While manufacturers advertise fuel efficiencies ranging from one to two liters per 100 kilometers, the study found an average consumption of six liters per 100 kilometers.
Researchers attribute the discrepancy to the dual-mode nature of PHEVs – the interplay between electric and combustion engines. Manufacturers have historically asserted minimal fuel usage when operating in electric mode, a claim the Fraunhofer study challenges. Patrick Plötz of the Fraunhofer Institute explained to German broadcaster SWR that the combustion engine is activated far more frequently than previously understood.
The analysis revealed significant variations in fuel consumption across different brands and models. German-manufactured PHEVs, particularly high-performance vehicles like Porsche models, exhibited the highest average fuel consumption, reaching approximately seven liters per 100 kilometers. In contrast, vehicles from Asian automakers such as Kia and Toyota, along with more affordable models from Ford and Renault, demonstrated fuel efficiencies closer to manufacturer claims, sometimes using less than one liter per 100 kilometers.
Porsche defended its fuel consumption figures, attributing variations to “differing usage patterns” and emphasizing that its measurements align with legal requirements. The company stated that its fuel consumption figures are “based on the legally prescribed EU measurement procedures,” which aim to ensure “uniform and comparable values across Europe.” Porsche acknowledged that “deviations from individual real-world consumption figures can arise due to different usage profiles and external conditions.”
The findings are fueling demands for revised emissions testing and stricter regulations. Plötz urged regulators to utilize real-world emissions data, suggesting that manufacturers failing to meet emissions limits in actual driving conditions should face penalties. He stated that current laboratory tests assume daily charging and short trips, conditions not representative of typical driver behavior.
The study also raises concerns about the accuracy of CO2 emission limits for vehicle fleets. Researchers argue that these limits need urgent adjustment to reflect real-world fuel consumption. The EU Commission, responsible for setting CO2 limits, declined to comment on the study’s findings when contacted by SWR.
The German Association of the Automotive Industry expressed confidence in the existing methods for determining fuel consumption and CO2 emissions. Yet, the Fraunhofer Institute’s analysis presents a significant challenge to the industry’s claims regarding the environmental performance of PHEVs and underscores the need for more realistic and comprehensive testing procedures.
