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Plug-in hybrid electric vehicles emit almost five times greater planet-heating pollution than lab-reported figures indicate, as per a new report.

Growing Gap Between Official and Real-World Emissions

Data reveals that PHEVs emit only 19% lower CO₂ than conventional gas and diesel cars, according to analysis carried out by a non-profit organization. This differs significantly with lab tests, which assumed a three-quarters decrease in emissions.

Analysts studied data from in-vehicle energy use monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” stated a lead researcher participating in the report. “That gap is widening and creates a serious problem. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles driven in electric power relative to total distance. The team determined that just 27% of driving was completed in EV mode, while lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, emission amounts were well above lab estimates. This occurred because electric motors were not strong sufficient to function independently, resulting to engines burning gasoline for nearly a third of the distance covered in electric mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV CO2 output enabled four large automaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 extra per year in running expenses than is estimated under lab conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a transport analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Pressure

Hybrid vehicles have recently been brought again into political discussions as carmakers have pressed the EU to relax CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with significant automotive industries.

Some high-level officials have suggested plug-in hybrids as a possible “flexibility” option to include in the regulation.

An independent energy economics specialist, who was not involved with the study, called the analysis a “very useful addition” after years in which parts of the car sector claimed there was insufficient information to accurately assess actual emissions.

“These findings demonstrate, beyond any doubt, that the gap in official and actual PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert said. “Any regulatory adjustments regarding PHEVs should be made with utmost care and in the light of that evidence.”