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

Widening Gap Between Official and Actual CO2 Output

Data shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit organization. This differs significantly with laboratory estimates, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use monitors of eight hundred thousand cars sold in Europe from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Real-world emissions are rising, while official figures are decreasing,” stated a senior analyst participating in the study. “That gap is growing and poses a serious issue. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Factors Driving the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to overall mileage. The team determined that just 27% of driving was done in EV mode, while official estimates assumed 84%.

Additionally, when operating in electric mode, emission amounts were significantly higher than official projections. This occurred because electric motors were insufficiently powerful enough to operate independently, leading to engines using gasoline for nearly one-third of the distance completed in EV mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed several large carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could spend about €500 more per year in running expenses than is assumed under laboratory conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the truth,” commented a automotive expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been brought again into political debates as carmakers have lobbied the EU to relax CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced heavy pressure from the car industry and resistance from EU countries with significant car manufacturing.

Several senior officials have suggested PHEVs as a possible “compromise” option to introduce in the regulation.

An independent energy policy specialist, who was unaffiliated with the research, described the report a “very useful contribution” after a long period in which parts of the car industry claimed there was insufficient information to properly evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional vehicles,” the expert stated. “Any policy adjustments concerning PHEVs should be made with utmost care and in the light of this evidence.”