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Plug-in hybrid electric vehicles produce almost 5x greater planet-heating pollution than lab-reported figures indicate, as per a new analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy organization. This contrasts sharply with laboratory estimates, which suggested a three-quarters decrease in emissions.

Researchers studied data from onboard fuel consumption meters of eight hundred thousand vehicles sold in the EU from 2021 and 2023. The team 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 CO2 output are rising, while official figures are falling,” stated a senior researcher involved in the study. “That gap is widening and poses a serious problem. Consequently, PHEVs emit almost as heavily as petrol cars.”

Primary Reasons Behind the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric power relative to total distance. The team determined that just a quarter of travel was done in electric mode, whereas lab assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution levels were well above official projections. This happened because electric motors were insufficiently powerful enough to function alone, resulting to engines burning gasoline for almost one-third of the distance completed in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV emissions allowed four large automaker groups to escape over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

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

“The strong claims that automakers often promote about their PHEV vehicles are obviously far from the mark,” commented a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been drawn back into political debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with significant car manufacturing.

Some high-level officials have suggested PHEVs as a possible “flexibility” option to introduce in the regulation.

One external energy economics expert, who was not involved with the research, described the report a “very useful contribution” after years in which segments of the automotive sector claimed there was too little information to properly assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or diesel vehicles,” the expert said. “Any regulatory changes regarding PHEVs should be made with utmost care and in the light of that data.”