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Plug-in hybrid cars produce nearly 5x greater global warming emissions than lab-reported data indicate, as per a new report.

Growing Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs emit just 19% lower CO₂ than traditional gas and diesel cars, according to analysis carried out by a advocacy organization. That differs significantly with lab estimates, which assumed a 75% reduction in pollution.

Researchers examined data from onboard fuel consumption monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” stated a lead analyst involved in the study. “This gap is growing and poses a significant problem. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Key Factors Behind the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of miles driven in electric mode relative to overall mileage. They found that just 27% of travel was completed in electric mode, whereas official estimates suggested 84%.

Additionally, when operating in EV mode, emission levels were well above official projections. This happened because electric motors were not strong enough to operate independently, resulting to combustion motors using gasoline for almost one-third of the travel covered in electric mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output enabled four large automaker companies to escape over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could spend approximately €500 more per year in operating costs than is estimated under laboratory conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the truth,” commented a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn back into political discussions as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced intense pressure from the car sector and resistance from EU countries with large automotive industries.

Several high-level politicians have proposed plug-in hybrids as a potential “flexibility” option to include in the legislation.

One external energy economics specialist, who was not involved with the research, called the report a “highly valuable contribution” after a long period in which parts of the automotive sector claimed there was insufficient information to properly assess real-world CO2 output.

“The results demonstrate, beyond any doubt, that the gap between lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional cars,” the expert stated. “Any policy adjustments regarding PHEVs should be made with extreme caution and considering that data.”