Plug-in Hybrids Burn Three Times More Fuel Than Manufacturers Claim, Landmark Study Finds
A groundbreaking analysis of approximately one million plug-in hybrid electric vehicles (PHEVs) has uncovered a stark discrepancy between advertised fuel efficiency and real-world performance. Conducted by the Fraunhofer Institute, this study represents the most extensive investigation of its kind to date, leveraging wireless data transmitted directly from vehicles on the road between 2021 and 2023.
The research reveals that PHEVs, which combine a petrol or diesel engine with a battery-powered electric motor, consume an average of six litres of fuel per 100 kilometres. This figure is roughly 300% higher than the one to two litres per 100km typically cited by manufacturers in official European Union certification tests.
Key Findings from the Fraunhofer Institute Analysis
Scientists identified the dual-mode operation of PHEVs as the primary culprit for elevated fuel usage. Contrary to manufacturer assertions that these vehicles use minimal or no fuel in electric mode, the study demonstrates that the combustion engine activates far more frequently than previously acknowledged.
Patrick Plötz of the Fraunhofer Institute explained to German broadcaster SWR that this frequent switching between power sources significantly drives up consumption. He emphasised the urgent need for regulators to incorporate real-world emissions data into compliance frameworks, suggesting penalties for manufacturers failing to meet on-road limits.
Performance Disparities Among Manufacturers
The analysis highlighted considerable variations in fuel consumption across different brands. German-manufactured PHEVs, particularly high-end models, recorded some of the highest averages. Porsche hybrids were the worst performers, using around seven litres per 100km when the electric motor was engaged and even more in combustion-only mode.
In contrast, more affordable models from Kia, Toyota, Ford, and Renault often consumed under one litre per 100km, representing up to 85% less fuel than Porsche equivalents. Porsche attributed these discrepancies to "differing usage patterns" and external factors like road conditions, maintaining that their measurements comply with EU legal standards.
Calls for Regulatory Reform and Industry Response
Researchers have urged EU regulators to revise measurement protocols to align with real-world findings, advocating for stricter controls on how PHEV fuel consumption is assessed. They argue that current CO2 fleet limits must be adjusted promptly to reflect actual emissions.
When contacted by SWR, the EU Commission declined to comment on the study's results. Meanwhile, the German Association of the Automotive Industry defended existing testing methods as reliable, despite the mounting evidence of their inadequacy.
This study underscores growing concerns among environmental groups regarding the true ecological footprint of plug-in hybrids, challenging their marketed image as energy-efficient alternatives to conventional vehicles.
