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Plug-in hybrid cars emit nearly 5x greater global warming emissions than lab-reported figures show, according to a new analysis.

Growing Gap Between Lab and Real-World Emissions

Statistics shows that PHEVs release only 19% lower CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a advocacy organization. That contrasts sharply with laboratory tests, which assumed a three-quarters decrease in emissions.

Researchers studied data from in-vehicle energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” stated a lead analyst participating in the study. “This discrepancy is growing and creates a significant issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to total distance. The team determined that only 27% of driving was done in EV mode, while official estimates suggested over four-fifths.

Even, when operating in EV mode, pollution amounts were significantly higher than official estimates. That occurred because EV motors were insufficiently powerful sufficient to function independently, resulting to combustion motors burning gasoline for almost one-third of the travel completed in electric mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV emissions enabled several major carmaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 more per year in operating expenses than is estimated under lab conditions.

“The strong statements that automakers often promote about their plug-in hybrid cars are clearly far from the mark,” commented a automotive expert. “Consumers are being misled into believing that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than standard gas and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have recently been drawn back into policy debates as carmakers have lobbied the European Union to weaken CO₂ standards. A planned ban on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive industry and resistance from member states with significant car industries.

Several high-level officials have suggested PHEVs as a potential “compromise” solution to include in the legislation.

One independent energy policy specialist, who was unaffiliated with the study, described the report a “highly valuable addition” after a long period in which segments of the car sector argued there was insufficient information to properly assess actual emissions.

“The results demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel vehicles,” they stated. “All policy adjustments regarding PHEVs should be made with utmost care and considering that evidence.”