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PHEVs produce almost 5x more global warming pollution than official data show, according to a new analysis.

Growing Gap In Official and Actual CO2 Output

Data shows that PHEVs release only 19% lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a non-profit organization. That contrasts sharply with lab estimates, which assumed a 75% decrease in pollution.

Researchers studied information from in-vehicle energy use meters of 800,000 vehicles registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” stated a senior researcher involved in the study. “This gap is growing and poses a significant issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Key Factors Driving the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery mode compared to overall distance. The team determined that just a quarter of driving was done in EV mode, while lab estimates suggested over four-fifths.

Additionally, when operating in EV mode, pollution levels were significantly higher than official projections. That happened because EV motors were not strong enough to operate alone, resulting to combustion motors burning gasoline for almost a third of the distance covered in electric mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four large automaker groups to avoid over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 extra per year in running costs than would be assumed under lab conditions.

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

Political Debate and Industry Lobbying

Plug-in hybrid cars have lately been drawn again into policy debates as automakers have pressed the EU to relax CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and opposition from member states with large car industries.

Several senior politicians have proposed plug-in hybrids as a possible “flexibility” solution to include in the regulation.

An external energy policy expert, who was not involved with the research, called the report a “highly valuable contribution” after years in which parts of the car sector argued there was insufficient data to properly evaluate actual emissions.

“The results show, without question, that the gap in official and real-world PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel cars,” they said. “All regulatory changes concerning PHEVs should be made with utmost caution and in the light of this evidence.”