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Plug-in hybrid cars produce almost 5x greater global warming pollution than official figures indicate, as per a recent analysis.

Widening Gap In Lab and Real-World Emissions

Data reveals that PHEVs release only 19% lower CO₂ than traditional petrol and diesel vehicles, based on research conducted by a non-profit group. This differs sharply with laboratory estimates, which assumed a 75% decrease in pollution.

Researchers examined data from onboard fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a lead analyst participating in the report. “That gap is growing and poses a significant problem. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Primary Factors Behind the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode compared to total mileage. They found that just a quarter of travel was done in EV mode, whereas official estimates assumed 84%.

Additionally, when running in EV mode, emission amounts were well above lab estimates. That occurred because EV motors were insufficiently powerful enough to function alone, leading to engines using gasoline for almost a third of the travel covered in EV mode.

Policy and Economic Consequences

Based on calculations, the lowballing of PHEV CO2 output enabled several major carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 more per year in running expenses than is estimated under laboratory conditions.

“The bold statements that automakers like to make about their PHEV vehicles are clearly far from the truth,” stated a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn back into policy debates as automakers have pressed the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with large car manufacturing.

Some senior politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the legislation.

One independent energy policy specialist, who was not involved with the study, called the analysis a “very useful contribution” after years in which parts of the automotive sector argued there was too little information to properly assess real-world CO2 output.

“The results show, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” the expert said. “All regulatory changes concerning PHEVs should be made with extreme caution and considering that data.”