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Plug-in hybrid cars emit nearly five times greater planet-heating pollution than official figures show, according to a new report.

Growing Gap In Official and Real-World CO2 Output

Data shows that PHEVs emit just 19% lower CO₂ than conventional gas and diesel cars, based on research conducted by a advocacy group. That differs significantly with lab tests, which suggested a three-quarters reduction in pollution.

Researchers studied information from onboard energy use monitors of 800,000 vehicles sold in the EU from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” stated a lead researcher involved in the report. “That gap is growing and poses a serious issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Key Factors Driving the Emissions Gap

Analysts attributed most of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to overall distance. They determined that just 27% of travel was completed in EV mode, whereas lab assumptions assumed 84%.

Even, when running in electric mode, pollution levels were well above lab projections. This occurred because EV motors were insufficiently powerful enough to function independently, resulting to engines burning gasoline for nearly one-third of the travel covered in electric mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV CO2 output allowed four major carmaker companies to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra per year in running expenses than is assumed under lab tests.

“The bold statements that automakers like to make about their PHEV vehicles are obviously way off the truth,” stated a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Political Debate and Automotive Pressure

Hybrid vehicles have lately been brought again into policy debates as carmakers have pressed the European Union to relax CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and resistance from member states with large automotive industries.

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

An external energy policy expert, who was not involved with the research, described the analysis a “very useful addition” after a long period in which segments of the automotive industry argued there was too little information to properly evaluate actual emissions.

“The results show, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel cars,” the expert stated. “All policy adjustments regarding PHEVs should be made with extreme care and in the light of that evidence.”