Plug-in Hybrid Reality Check: Real-World Emissions Far Exceed Official Figures
A recent study by the Fraunhofer Institute sheds light on a significant discrepancy between the advertised and actual performance of plug-in hybrid vehicles (PHEVs). The research reveals that PHEV owners are not utilizing the electric driving capabilities of their vehicles to the extent anticipated, resulting in considerably higher fuel consumption and CO2 emissions than official testing standards suggest.
While homologation standards estimate an average fuel consumption of around 1.5 liters per 100 kilometers, real-world data indicates an average of 5.9 liters per 100 kilometers. This substantial difference stems from the fact that PHEVs complete less than one-third of their journeys solely on electric power, falling short of the higher proportions assumed by current standards.
Brand Disparities in Charging Behavior
The study highlights a notable variation in charging habits among different car brands. Drivers of Citroën, Peugeot, DS, Opel, Mazda, and Toyota demonstrate relatively consistent charging behavior, with Toyota achieving an electric share of up to 42.8% in total consumption.
Conversely, owners of premium German brands – Audi, BMW, and Mercedes – predominantly rely on petrol or diesel power. Porsche owners exhibit the lowest utilization of electric mode, with some reportedly not even unpacking their charging cables. For Porsche vehicles, electricity accounts for only 0.8% of total energy consumption, averaging just 7 kWh charged over 27,000 kilometers – insufficient for a full battery capacity.
A PHEV operating with a depleted battery averages 7.4 liters per 100 kilometers, and in some Porsche models, this figure can be even higher. Data from Auto Motor und Sport indicates that models like the Porsche Cayenne and Mercedes GLE achieve a total average consumption between six and nine liters, with electricity contributing only around fifteen percent.
Vehicle Size and Electric Share
The study also reveals a correlation between vehicle size and charging frequency. Larger SUVs are recharged less often, while upper mid-range cars like the BMW 5 Series and Audi A6 achieve an electric energy share of 25-30%. Lower mid-range vehicles, such as the Toyota Prius, demonstrate higher electric shares, ranging from 35 to 43 percent. However, even these figures remain below the levels projected by current standards.
Hybrid Mode Impact on Consumption
Beyond charging habits, the way drivers utilize electric mode influences real-world consumption. Drivers often opt for hybrid mode, which combines the internal combustion engine and electric motor. While this mode can achieve an average fuel consumption of 2.8 liters per 100 kilometers with a charged battery, researchers found the combustion engine is engaged more frequently than anticipated. Tagesschau reported this consumption figure was surprising, even to the researchers themselves.
However, brands like Toyota, Renault, Ford, and Kia, which also offer self-charging hybrid models with smaller batteries, demonstrate lower consumption in hybrid mode, regardless of battery charge. Conversely, brands without comparable non-plug-in hybrids, such as VW and BMW, tend to exhibit poorer results.
Calls for Regulatory Adjustments
The Fraunhofer Institute’s study raises questions about the accuracy of current European standards for PHEVs. The significant gap between stated and real-world consumption suggests a require for revised testing methodologies.
Currently, low reported consumption figures for PHEVs enable manufacturers to meet stringent fleet emission limits. Researchers propose increased support for range-extender vehicles, like the Opel Ampera and BMW i3 REX, which prioritize electric driving and limit internal combustion engine use to battery depletion or extended routes. These vehicles are designed to operate on electricity for approximately 90% of the time, with the combustion engine serving as a backup power source.