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Plug-in hybrid cars release almost five times greater planet-heating pollution than lab-reported data indicate, according to a recent analysis.

Widening Discrepancy In Lab and Actual CO2 Output

Statistics reveals that PHEVs emit only 19% lower CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a non-profit organization. That contrasts sharply with lab tests, which suggested a 75% reduction in pollution.

Analysts examined information from in-vehicle energy use meters of eight hundred thousand cars registered in the EU between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” said a senior researcher participating in the report. “That discrepancy is growing and creates a significant issue. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Researchers linked the majority of the difference to overestimates of the “electric driving share” – the ratio of miles driven in electric mode compared to overall mileage. They found that only a quarter of travel was done in EV mode, while lab estimates assumed over four-fifths.

Even, when running in electric mode, pollution amounts were well above official projections. That occurred because electric motors were not strong sufficient to function independently, resulting to combustion motors burning fossil fuels for nearly a third of the travel covered in electric mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV CO2 output allowed several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would pay about €500 extra per year in operating costs than is estimated under laboratory tests.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” stated a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Political Discussion and Automotive Lobbying

Hybrid cars have lately been brought back into political debates as automakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and opposition from member states with significant car manufacturing.

Several high-level officials have suggested PHEVs as a possible “compromise” solution to introduce in the regulation.

An external energy policy expert, who was unaffiliated with the study, called the analysis a “very useful addition” after years in which segments of the automotive industry claimed there was insufficient information to properly evaluate actual emissions.

“The results demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional cars,” they said. “All regulatory changes regarding PHEVs should be made with extreme care and in the light of this data.”