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PHEVs produce almost five times more global warming pollution than official data indicate, according to a new report.

Growing Discrepancy In Official and Actual CO2 Output

Data reveals that PHEVs release only 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a advocacy group. That differs significantly with lab tests, which suggested a 75% reduction in pollution.

Researchers studied data from onboard energy use monitors of 800,000 vehicles registered in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” said a senior researcher involved in the report. “This discrepancy is growing and poses a serious issue. Consequently, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power relative to total distance. They determined that only a quarter of driving was done in electric mode, whereas official assumptions suggested 84%.

Additionally, when operating in electric mode, pollution amounts were significantly higher than lab estimates. That happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to engines using gasoline for almost a third of the travel covered in electric mode.

Policy and Financial Implications

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

Furthermore, owners of PHEVs would spend about €500 extra annually in running expenses than is assumed under lab tests.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are obviously far from the mark,” commented a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have recently been drawn again into policy debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with large car industries.

Several high-level politicians have suggested plug-in hybrids as a potential “compromise” solution to include in the regulation.

An independent energy economics specialist, who was unaffiliated with the study, called the analysis a “very useful addition” after years in which segments of the car sector argued there was too little data to accurately evaluate actual emissions.

“These findings show, without question, that the gap in official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel cars,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and considering this evidence.”