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Plug-in hybrid cars emit nearly 5x more planet-heating pollution than official data indicate, as per a recent report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, according to analysis carried out by a non-profit organization. This differs significantly with laboratory tests, which assumed a three-quarters reduction in pollution.

Analysts examined data from onboard fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” stated a senior analyst participating in the study. “This discrepancy is widening and poses a serious problem. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of miles driven in electric power relative to total mileage. They determined that only 27% of driving was done in electric mode, whereas lab assumptions assumed 84%.

Additionally, when operating in EV mode, emission amounts were well above official estimates. That occurred because EV motors were not strong enough to operate independently, leading to engines burning gasoline for nearly a third of the distance covered in electric mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV emissions allowed several major automaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay about €500 extra annually in running expenses than would be estimated under lab conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating costs.”

Political Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought back into political discussions as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and resistance from member states with significant automotive industries.

Several senior politicians have proposed PHEVs as a potential “flexibility” solution to introduce in the regulation.

An independent energy economics specialist, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after years in which segments of the automotive sector argued there was insufficient data to properly evaluate actual emissions.

“These findings show, without question, that the difference in official and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or diesel cars,” the expert said. “Any regulatory changes regarding PHEVs should be made with utmost caution and in the light of this evidence.”