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Plug-in hybrid cars produce nearly five times greater global warming pollution than lab-reported figures indicate, according to a recent analysis.

Growing Gap Between Lab and Real-World Emissions

Data shows that PHEVs release only 19% lower CO₂ than traditional petrol and diesel cars, according to research conducted by a advocacy group. That contrasts sharply with laboratory tests, which assumed a 75% reduction in pollution.

Researchers studied data from onboard energy use monitors of 800,000 cars sold in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” said a senior researcher participating in the report. “This gap is growing and creates a serious problem. As a result, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to overall distance. They found that only 27% of travel was completed in EV mode, whereas official estimates suggested 84%.

Additionally, when operating in EV mode, pollution amounts were well above official projections. This occurred because electric motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors using fossil fuels for nearly one-third of the travel covered in EV mode.

Policy and Economic Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed four large automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs could spend about €500 more annually in operating costs than would be estimated under lab tests.

“The bold statements that automakers often promote about their PHEV vehicles are obviously far from the truth,” commented a automotive expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Discussion and Automotive Lobbying

Hybrid cars have lately been brought again into policy discussions as automakers have pressed the EU to relax CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with large automotive industries.

Several senior officials have proposed PHEVs as a potential “compromise” solution to include in the regulation.

An independent energy economics specialist, who was not involved with the study, described the analysis a “very useful addition” after a long period in which parts of the automotive industry argued there was insufficient information to properly assess real-world CO2 output.

“The results demonstrate, beyond any doubt, that the gap in lab and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” the expert stated. “All regulatory changes concerning PHEVs should be made with extreme care and considering this data.”