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Plug-in hybrid electric vehicles produce almost five times more planet-heating emissions than official figures indicate, as per a new analysis.

Widening Discrepancy In Lab and Actual Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit group. This differs significantly with laboratory estimates, which suggested a 75% reduction in pollution.

Researchers studied information from in-vehicle fuel consumption meters of 800,000 vehicles registered in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” said a senior researcher participating in the study. “That gap is growing and creates a serious problem. As a result, PHEVs pollute almost as much as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of miles driven in electric power relative to overall mileage. They determined that only a quarter of travel was done in EV mode, while lab estimates assumed 84%.

Additionally, when operating in electric mode, emission amounts were well above official projections. That occurred because EV motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors burning gasoline for almost one-third of the travel completed in EV mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV CO2 output enabled several major automaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs would pay approximately €500 extra per year in running expenses than is estimated under lab tests.

“The bold claims that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” stated a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have lately been drawn back into policy discussions as automakers have lobbied the European Union to relax CO₂ targets. A proposed ban on new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large automotive manufacturing.

Several senior politicians have suggested PHEVs as a possible “compromise” option to include in the regulation.

An independent energy economics specialist, who was not involved with the research, called the report a “highly valuable addition” after a long period in which parts of the automotive industry argued there was insufficient data to accurately assess real-world emissions.

“These findings show, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” they said. “All regulatory changes concerning PHEVs should be implemented with extreme care and in the light of that evidence.”