Real-world fuel consumption for plug-in hybrid vehicles is significantly higher than official figures suggest, according to a new study. Data from approximately one million plug-in hybrids registered in Europe reveals an average fuel consumption of 5.9 liters per 100 kilometers, a figure nearly three times higher than the 1 to 2 liters per 100 kilometers reported in vehicle homologation documents.
The discrepancy stems from drivers not charging their vehicles as frequently as assumed in laboratory tests and adopting more dynamic driving styles, leading to more frequent activation of the internal combustion engine. This finding has implications for automakers and regulators as they navigate the transition to electric vehicles and strive for more accurate emissions reporting.
Official fuel consumption figures are calculated using a standardized laboratory test across the European Union, simulating a mixed driving cycle – urban, suburban, and highway. However, the analysis conducted by the Fraunhofer Institute in Germany, examining vehicle data from 2021 to 2023, paints a different picture of on-road performance.
“People don’t charge often enough and don’t employ the electric battery enough, so they practically carry it around for nothing,” said Mihai Duguleană, from the Department of Automotive and Transport at Transilvania University.
Driving habits similarly play a crucial role. Rapid acceleration and high speeds trigger more frequent use of the gasoline engine. “We don’t use the car as it was tested, we use it differently. Much more aggressively, with much higher speeds, we brake suddenly, accelerate suddenly, we excessively use the heating in the cabin,” explained Cristian Trifan, technical director of an auto dealership.
EU to Revise Hybrid Vehicle Fuel Consumption Calculations
The European Commission has already decided to modify the methodology for calculating fuel consumption in plug-in hybrid vehicle homologation procedures. Until 2024, the official methodology assumed these vehicles primarily operated in electric mode, resulting in incredibly low consumption values in official documents and discrepancies exceeding 300% compared to real-world consumption.
From 2025, the estimated proportion of electric driving has been reduced, aiming to narrow the gap between official and real-world consumption to approximately 100%. Further adjustments to the calculation model are planned for next year, with the goal of reducing the deviation between homologated and actual consumption to around 40%.
Adrian Sandu, director general of the Constructors Association, cautioned about the study’s methodology, stating, “This study doesn’t say under what conditions the tests were done, it doesn’t clearly state how much was driven in the city, whether the battery was charged.”
It’s worth noting that a difference between homologated and real-world fuel consumption also exists for gasoline and diesel vehicles, averaging around 20%.
