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Plug-in hybrid cars emit almost five times greater planet-heating pollution than official data indicate, according to a new analysis.

Growing Gap In Lab and Real-World CO2 Output

Data reveals that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy group. That contrasts significantly with laboratory tests, which suggested a three-quarters decrease in pollution.

Researchers studied data from onboard fuel consumption meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” stated a lead analyst participating in the report. “That discrepancy is growing and creates a serious issue. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Primary Reasons Behind the Discrepancy

Analysts linked most of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in electric mode compared to overall mileage. They found that only 27% of travel was completed in EV mode, while official assumptions assumed 84%.

Additionally, when running in EV mode, pollution amounts were significantly higher than lab projections. This occurred because EV motors were insufficiently powerful enough to function alone, resulting to engines burning gasoline for almost a third of the distance completed in EV mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output enabled four large carmaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay approximately €500 more per year in running expenses than is estimated under laboratory conditions.

“The bold claims that automakers like to make about their PHEV vehicles are clearly far from the mark,” stated a transport analyst. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little better than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn again into political debates as automakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with large automotive manufacturing.

Several high-level officials have suggested PHEVs as a possible “flexibility” solution to introduce in the legislation.

An independent energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the car industry argued there was too little information to properly assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” they said. “Any policy adjustments concerning PHEVs should be implemented with extreme caution and considering that evidence.”