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PHEVs emit nearly 5x greater global warming pollution than lab-reported figures show, according to a new analysis.

Growing Discrepancy Between Lab and Actual Emissions

Statistics reveals that PHEVs release just one-fifth less CO₂ than traditional gas and diesel cars, according to research conducted by a advocacy organization. That differs significantly with laboratory estimates, which suggested a three-quarters reduction in emissions.

Researchers studied information from in-vehicle fuel consumption meters 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 official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” stated a lead analyst involved in the study. “That discrepancy is growing and creates a serious problem. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Factors Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery power compared to total mileage. The team found that just a quarter of travel was completed in electric mode, while lab estimates suggested over four-fifths.

Additionally, when running in electric mode, emission levels were well above lab estimates. This occurred because EV motors were insufficiently powerful enough to operate independently, resulting to combustion motors burning fossil fuels for nearly a third of the travel covered in EV mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions enabled several large automaker companies to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend approximately €500 more per year in running costs than is estimated under lab conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Political Discussion and Automotive Lobbying

Hybrid cars have recently been brought again into policy debates as automakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and resistance from member states with significant automotive industries.

Several senior politicians have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

One independent energy economics specialist, who was unaffiliated with the research, described the report a “highly valuable contribution” after a long period in which segments of the car industry claimed there was too little data to accurately evaluate real-world CO2 output.

“The results show, beyond any doubt, that the difference in official and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with utmost caution and in the light of that evidence.”