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PHEVs emit nearly five times more planet-heating pollution than lab-reported figures show, according to a recent report.

Widening Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs release just 19% lower CO₂ than traditional gas and diesel vehicles, according to research carried out by a advocacy organization. That contrasts sharply with lab tests, which suggested a 75% reduction in emissions.

Researchers examined information from onboard fuel consumption meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are falling,” said a lead researcher participating in the study. “This gap is growing and creates a significant issue. As a result, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Behind the Discrepancy

Researchers linked most of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in battery mode relative to total mileage. They determined that just 27% of travel was completed in electric mode, while official estimates assumed over four-fifths.

Even, when running in EV mode, emission levels were well above official projections. That happened because electric motors were insufficiently powerful sufficient to function alone, leading to engines using gasoline for nearly a third of the distance covered in EV mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV emissions allowed several major automaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 more annually in operating expenses than would be estimated under lab conditions.

“The strong statements that manufacturers like to make about their PHEV vehicles are clearly way off the mark,” stated a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought again into policy debates as automakers have lobbied the EU to relax CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car industry and resistance from EU countries with significant automotive manufacturing.

Several senior politicians have suggested PHEVs as a potential “compromise” solution to introduce in the legislation.

An external energy policy specialist, who was unaffiliated with the study, called the report a “very useful contribution” after a long period in which segments of the car sector claimed there was too little information to accurately assess actual emissions.

“These findings demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel vehicles,” the expert said. “All policy adjustments regarding PHEVs should be made with utmost care and considering that evidence.”