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Plug-in hybrid electric vehicles emit nearly 5x more planet-heating emissions than official data show, as per a new report.

Growing Gap In Lab and Real-World CO2 Output

Data reveals that PHEVs emit just 19% lower CO₂ than traditional petrol and diesel vehicles, based on research conducted by a advocacy organization. That contrasts sharply with laboratory estimates, which suggested a three-quarters decrease in pollution.

Researchers examined data from onboard fuel consumption monitors of 800,000 cars sold in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” said a senior researcher involved in the study. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in electric power compared to overall mileage. The team found that just a quarter of travel was completed in EV mode, while official estimates assumed over four-fifths.

Additionally, when running in EV mode, emission amounts were significantly higher than official projections. This occurred because EV motors were insufficiently powerful enough to operate alone, leading to engines burning fossil fuels for almost a third of the travel covered in EV mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV emissions allowed several major automaker groups to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs would spend about €500 more per year in operating expenses than is estimated under laboratory conditions.

“The strong claims that manufacturers like to make about their PHEV vehicles are clearly way off the mark,” commented a automotive analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little improved than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into policy discussions as automakers have pressed the EU to relax CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the car sector and opposition from member states with significant automotive manufacturing.

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

An external energy policy expert, who was not involved with the research, described the report a “highly valuable contribution” after a long period in which parts of the automotive industry argued there was insufficient information to accurately evaluate real-world CO2 output.

“The results demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel vehicles,” the expert stated. “Any regulatory changes concerning PHEVs should be made with extreme caution and considering this data.”