Plug-in hybrids use three times more fuel than manufacturers claim, analysis finds | Electric, hybrid and low-emission cars

Plug-in hybrid electric cars (PHEV) use far more fuel on the road than officially claimed by their manufacturers, a large-scale analysis of around a million such vehicles has shown.

The Fraunhofer Institute carried out what is considered the most comprehensive study of its kind to date, using data transmitted wirelessly from PHEVs from various manufacturers while they were on the move.

The affected cars were all produced between 2021 and 2023. The transmitted data allowed analysts to determine their precise and actual fuel consumption, as opposed to that stated in the vehicles’ official EU-approved certification.

PHEVs, cars that combine a gasoline or diesel engine with a battery-powered electric motor charged from an external energy point, offer drivers the flexibility of being able to switch between the environmentally safer energy source and the more conventional, but more environmentally damaging, energy source when conditions permit. Manufacturers generally market their vehicles as energy efficient. On paper at least, these vehicles would consume much less fuel, between one and two liters per 100 km, than conventional cars. However, environmental groups have long expressed skepticism about these claims.

According to the study, these vehicles require on average six liters per 100 km, or approximately 300% more fuel than previously indicated.

Scientists from the Fraunhofer Institute found that the main reason for higher fuel consumption than indicated was precisely because PHEVs use two different modes, the electric motor and the combustion engine, alternating between the two. Until now, manufacturers claimed that vehicles consumed little or almost no fuel when in electric mode. Studies have shown that this is not the case.

Patrick Plötz of the Fraunhofer Institute told German broadcaster SWR that he suspects the combustion engine in PHEVs ignites much more frequently than previously thought. German-made PHEVs were among those with the highest average fuel consumption, with the top-of-the-line Porsche model performing the worst.

Plötz urged regulators to use real-world emissions data. “You could then say that a manufacturer who does not respect the (emissions) limits on the road could have to pay a penalty,” he said.

Porsche hybrids consumed more fuel – around seven liters per 100 km – than other PHEVs when the electric motor kicks in, and significantly more than non-PHEVs in combustion engine mode. The lowest fuel consumption levels were seen in the cheapest segment of the PHEV market, in Kia, Toyota, Ford and Renault vehicles, which often consumed less than a liter per 100km, up to 85% less fuel than the Porsche.

Asked by SWR, which published the results of the study on Wednesday, how to explain this discrepancy, Porsche mentioned “different modes of use”, which, according to it, influenced fuel consumption. Porsche insisted that its fuel consumption measurements complied with legal requirements, saying: “The fuel consumption figures for our vehicles are based on the measurement procedures legally prescribed by the EU. » These, according to the text, guarantee “uniform and comparable values ​​across Europe”.

“Deviations from actual individual consumption figures may arise due to different usage profiles and external conditions,” such as road conditions or driver behavior, the company told SWR.

Scientists have called on European regulators to adjust their measurements to match real-world results, calling for tighter controls on how the fuel consumption of plug-in hybrids is measured. According to the results, the CO2 limits that a car manufacturer’s vehicle fleet is allowed to emit on average need to be adjusted urgently.

Contacted by SWR, the European Commission, responsible for CO2 limits, declined to comment on these findings.

The German Automobile Industry Association believes that existing measurements for determining fuel consumption and CO2 emissions are reliable.