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Plug-in hybrid cars produce nearly five times more global warming emissions than official figures indicate, according to a new report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Statistics shows that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel vehicles, based on analysis conducted by a non-profit group. This contrasts significantly with lab estimates, which suggested a three-quarters decrease in pollution.

Researchers studied information from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official figures are decreasing,” stated a senior researcher participating in the study. “This gap is growing and creates a serious issue. As a result, PHEVs emit nearly as much as petrol vehicles.”

Primary Factors Behind the Discrepancy

Analysts linked most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in battery power compared to overall mileage. The team found that just 27% of driving was completed in electric mode, whereas lab assumptions assumed 84%.

Additionally, when running in EV mode, pollution levels were well above lab estimates. That occurred because EV motors were insufficiently powerful enough to function alone, resulting to engines burning fossil fuels for nearly a third of the travel covered in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV emissions enabled four major carmaker groups to avoid over €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 extra annually in operating expenses than would be assumed under lab tests.

“The bold claims that manufacturers like to make about their PHEV cars are obviously far from the mark,” stated a transport analyst. “Consumers are being duped into thinking that by buying 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 production, and operating costs.”

Political Debate and Industry Lobbying

Hybrid cars have recently been brought back into political discussions as carmakers have pressed the European Union to weaken CO₂ targets. A proposed prohibition on new internal combustion cars in 2035 has faced intense lobbying from the car industry and opposition from EU countries with large car manufacturing.

Several senior politicians have suggested PHEVs as a possible “flexibility” option to include in the legislation.

An independent energy economics specialist, who was not involved with the study, described the report a “highly valuable addition” after years in which segments of the car industry argued there was too little information to properly evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” they said. “All regulatory changes concerning PHEVs should be implemented with extreme caution and in the light of this evidence.”