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Plug-in hybrid electric vehicles release nearly 5x greater global warming pollution than official figures indicate, according to a new analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Data reveals that PHEVs release just 19% less CO₂ than traditional petrol and diesel cars, based on analysis carried out by a advocacy organization. That differs significantly with lab tests, which suggested a three-quarters reduction in pollution.

Researchers studied data from in-vehicle fuel consumption meters of eight hundred thousand cars sold in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” stated a lead analyst involved in the study. “This gap is widening and poses a serious problem. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric mode relative to total distance. The team found that only a quarter of driving was done in EV mode, whereas official estimates assumed 84%.

Additionally, when running in electric mode, pollution levels were significantly higher than lab projections. This happened because EV motors were not strong enough to operate independently, resulting to combustion motors using gasoline for almost a third of the travel covered in EV mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions allowed several major automaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay approximately €500 extra per year in operating costs than is assumed under lab conditions.

“The bold statements that automakers like to make about their PHEV vehicles are obviously way off the mark,” commented a automotive analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating costs.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn back into political debates as carmakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car industry and opposition from EU countries with large car manufacturing.

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

One independent energy economics specialist, who was not involved with the research, called the report a “highly valuable contribution” after years in which parts of the car industry claimed there was too little data to accurately assess actual CO2 output.

“These findings demonstrate, without question, that the gap in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they said. “All regulatory changes regarding PHEVs should be implemented with extreme care and considering that evidence.”