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PHEVs emit nearly five times greater planet-heating emissions than lab-reported data indicate, according to a new analysis.

Widening Gap In Official and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel cars, according to research carried out by a non-profit organization. That contrasts significantly with laboratory tests, which assumed a 75% reduction in pollution.

Researchers studied information from in-vehicle fuel consumption meters of eight hundred thousand cars registered in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” stated a senior researcher participating in the study. “This gap is growing and creates a serious issue. Consequently, PHEVs emit almost as much as petrol cars.”

Key Reasons Behind the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of miles driven in battery mode compared to total mileage. The team determined that only a quarter of travel was completed in EV mode, whereas lab assumptions assumed over four-fifths.

Even, when operating in electric mode, emission amounts were well above official estimates. That happened because EV motors were not strong sufficient to function alone, leading to engines using fossil fuels for almost one-third of the distance completed in electric mode.

Policy and Economic Implications

Based on calculations, the underestimation of PHEV emissions enabled several large carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 more per year in running costs than would be assumed under lab tests.

“The strong claims that manufacturers like to make about their PHEV cars are obviously way off the truth,” stated a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have recently been drawn back into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced heavy pressure from the car sector and resistance from member states with large car manufacturing.

Several senior officials have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

An independent energy policy specialist, who was not involved with the study, described the analysis a “highly valuable contribution” after years in which segments of the automotive industry argued there was too little data to properly assess actual emissions.

“The results show, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they said. “All regulatory changes regarding PHEVs should be made with extreme care and considering this evidence.”