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Plug-in hybrid cars produce nearly 5x greater global warming emissions than official data show, as per a new report.

Widening Gap In Official and Actual Emissions

Data shows that PHEVs release just 19% less CO₂ than traditional gas and diesel cars, according to analysis conducted by a advocacy organization. This differs significantly with laboratory estimates, which suggested a three-quarters decrease in emissions.

Analysts examined information from in-vehicle fuel consumption meters of 800,000 vehicles sold in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” said a senior researcher involved in the report. “This discrepancy is growing and poses a serious problem. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Key Reasons Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to total mileage. They found that only a quarter of driving was completed in EV mode, while official assumptions assumed 84%.

Additionally, when operating in EV mode, pollution levels were well above official projections. That happened because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors using gasoline for almost a third of the travel completed in EV mode.

Regulatory and Financial Implications

According to calculations, the lowballing of PHEV emissions enabled several large automaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 extra per year in running expenses than would be estimated under lab conditions.

“The strong statements that automakers often promote about their PHEV cars are clearly far from the truth,” stated a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn again into political debates as carmakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on new internal combustion cars in 2035 has faced intense pressure from the car sector and resistance from member states with large automotive manufacturing.

Several high-level politicians have proposed plug-in hybrids as a potential “compromise” solution to include in the regulation.

One external energy economics specialist, who was not involved with the research, called the report a “very useful contribution” after years in which segments of the car industry argued there was too little data to accurately assess actual emissions.

“The results demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert stated. “All policy adjustments regarding PHEVs should be made with extreme care and considering this data.”