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Plug-in hybrid cars emit almost five times greater planet-heating emissions than lab-reported data indicate, as per a new report.

Growing Gap Between Lab and Actual Emissions

Statistics reveals that PHEVs emit just 19% less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a advocacy group. This differs sharply with laboratory estimates, which assumed a three-quarters decrease in pollution.

Researchers studied information from onboard fuel consumption meters of 800,000 vehicles sold in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are falling,” said a senior analyst participating in the study. “That discrepancy is widening and poses a serious issue. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Key Reasons Behind the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in battery power compared to overall mileage. They determined that just a quarter of travel was completed in EV mode, whereas official assumptions suggested over four-fifths.

Even, when running in EV mode, pollution amounts were well above official estimates. This occurred because EV motors were not strong enough to operate independently, resulting to engines burning gasoline for nearly a third of the distance completed in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four large automaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 extra annually in operating expenses than is assumed under laboratory conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” commented a automotive analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Pressure

Hybrid cars have recently been brought back into policy debates as automakers have pressed the EU to relax CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from member states with large car manufacturing.

Several high-level officials have proposed plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

An independent energy policy expert, who was not involved with the study, described the report a “highly valuable contribution” after a long period in which segments of the car sector argued there was too little information to properly evaluate real-world emissions.

“The results show, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or diesel vehicles,” they said. “Any policy adjustments regarding PHEVs should be made with extreme care and considering that data.”