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Plug-in hybrid cars release nearly five times more planet-heating pollution than lab-reported data indicate, according to a new analysis.

Widening Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs release only one-fifth lower CO₂ than traditional petrol and diesel cars, according to research conducted by a advocacy group. This differs sharply with lab tests, which assumed a three-quarters decrease in pollution.

Analysts studied data from in-vehicle fuel consumption meters of eight hundred thousand cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are falling,” stated a senior researcher participating in the study. “That discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Primary Reasons Driving the Discrepancy

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in battery power relative to overall distance. The team found that just 27% of driving was done in electric mode, while official estimates suggested over four-fifths.

Even, when operating in electric mode, pollution amounts were significantly higher than official projections. That happened because electric motors were insufficiently powerful enough to function alone, leading to combustion motors using fossil fuels for nearly a third of the distance completed in EV mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed four large automaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay about €500 more annually in running costs than would be assumed under lab tests.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are obviously way off the mark,” stated a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little improved than regular gas and diesel cars in terms of fuel use, CO₂ production, and running costs.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been brought again into political debates as automakers have pressed the EU to relax CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and resistance from member states with significant automotive manufacturing.

Some senior politicians have suggested PHEVs as a possible “compromise” solution to include in the legislation.

An independent energy policy expert, who was unaffiliated with the study, called the report a “highly valuable addition” after years in which segments of the car sector argued there was insufficient data to properly assess actual CO2 output.

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