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Plug-in hybrid electric vehicles release almost five times more planet-heating emissions than lab-reported figures show, as per a recent analysis.

Growing Discrepancy Between Official and Real-World CO2 Output

Data reveals that PHEVs release just one-fifth less CO₂ than traditional gas and diesel cars, according to analysis conducted by a advocacy organization. This differs significantly with lab tests, which suggested a 75% reduction in pollution.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 cars registered in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” said a lead analyst participating in the report. “This discrepancy is growing and poses a significant problem. As a result, PHEVs emit nearly as much as gasoline cars.”

Key Factors Driving the Emissions Gap

Analysts linked most of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in electric power compared to total mileage. The team found that only a quarter of travel was completed in electric mode, whereas lab estimates suggested 84%.

Even, when running in electric mode, emission amounts were significantly higher than lab projections. This occurred because electric motors were insufficiently powerful sufficient to function independently, leading to engines burning gasoline for almost a third of the distance covered in electric mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV emissions allowed several major automaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 extra annually in operating costs than would be estimated under laboratory conditions.

“The strong claims that automakers like to make about their plug-in hybrid cars are clearly way off the mark,” commented a automotive expert. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Political Discussion and Automotive Pressure

Hybrid cars have recently been drawn again into policy debates as automakers have pressed the European Union to relax CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with large car industries.

Several senior politicians have suggested PHEVs as a potential “flexibility” solution to introduce in the legislation.

An external energy economics specialist, who was unaffiliated with the research, described the report a “highly valuable contribution” after a long period in which parts of the automotive sector argued there was insufficient information to properly evaluate real-world emissions.

“These findings demonstrate, without question, that the gap in lab and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” the expert said. “Any regulatory changes concerning PHEVs should be made with extreme caution and in the light of that data.”