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Plug-in hybrid cars release nearly 5x more global warming emissions than lab-reported data show, as per a new report.

Widening Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs emit just 19% lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a advocacy organization. That differs significantly with lab estimates, which assumed a three-quarters decrease in emissions.

Researchers examined data from onboard energy use meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a senior researcher participating in the study. “That gap is growing and creates a serious problem. Consequently, PHEVs emit almost as heavily as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to total mileage. They found that just a quarter of travel was completed in EV mode, while official estimates suggested 84%.

Additionally, when operating in EV mode, emission levels were well above official projections. This occurred because EV motors were not strong sufficient to function independently, resulting to combustion motors burning gasoline for nearly one-third of the travel covered in electric mode.

Regulatory and Financial Implications

Based on calculations, the lowballing of PHEV emissions enabled several large automaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 extra annually in running costs than would be estimated under lab tests.

“The bold statements that manufacturers like to make about their PHEV cars are obviously way off the truth,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into political discussions as carmakers have pressed the EU to relax CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the car sector and resistance from member states with large automotive manufacturing.

Several high-level officials have proposed PHEVs as a potential “compromise” option to include in the regulation.

An independent energy economics specialist, who was unaffiliated with the research, called the report a “very useful contribution” after years in which segments of the automotive industry claimed there was insufficient data to accurately evaluate actual CO2 output.

“These findings show, without question, that the gap between lab and actual PHEV energy use and CO₂ output is significantly larger than for petrol or diesel cars,” the expert said. “Any regulatory adjustments concerning PHEVs should be made with extreme care and considering this evidence.”