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Plug-in hybrid electric vehicles produce nearly 5x more global warming emissions than official figures show, according to a new analysis.

Widening Discrepancy In Official and Real-World CO2 Output

Statistics shows that PHEVs release only 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a advocacy organization. This differs sharply with lab tests, which suggested a three-quarters reduction in pollution.

Analysts studied information from onboard fuel consumption monitors of 800,000 vehicles sold in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” stated a senior analyst participating in the report. “That discrepancy is growing and creates a serious problem. As a result, PHEVs emit nearly as much as gasoline cars.”

Primary Factors Driving the Discrepancy

Researchers linked the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in electric mode relative to overall mileage. The team found that only a quarter of travel was completed in electric mode, whereas official estimates assumed 84%.

Even, when running in electric mode, emission amounts were significantly higher than lab projections. This occurred because electric motors were not strong sufficient to function independently, resulting to engines burning gasoline for almost a third of the travel covered in electric mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output enabled several large carmaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

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

“The strong statements that automakers often promote about their PHEV cars are obviously far from the truth,” commented a transport analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Discussion and Automotive Pressure

Hybrid cars have recently been drawn again into political discussions as carmakers have lobbied the European Union to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with significant automotive manufacturing.

Several senior officials have proposed PHEVs as a possible “flexibility” option to include in the legislation.

An independent energy economics specialist, who was unaffiliated with the study, described the report a “highly valuable contribution” after years in which segments of the car sector claimed there was insufficient data to properly assess actual CO2 output.

“The results demonstrate, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” the expert said. “Any policy adjustments regarding PHEVs should be made with extreme care and considering that data.”