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Plug-in hybrid cars emit almost five times more planet-heating pollution than official data indicate, as per a new report.

Widening Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs release only 19% lower CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a advocacy group. This differs sharply with lab estimates, which suggested a 75% decrease in emissions.

Analysts studied information from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” stated a lead researcher participating in the study. “That gap is widening and poses a serious problem. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Researchers linked most of the difference to inflated estimates of the “utility factor” – the percentage of kilometers travelled in electric power compared to overall distance. They found that just a quarter of travel was completed in EV mode, whereas official assumptions suggested 84%.

Even, when running in electric mode, pollution amounts were significantly higher than lab projections. This occurred because EV motors were not strong sufficient to operate alone, leading to combustion motors burning gasoline for almost one-third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed four large automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend about €500 extra annually in running costs than would be assumed under lab tests.

“The strong claims that automakers like to make about their PHEV vehicles are obviously way off the truth,” commented a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little better than standard petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have lately been drawn back into policy debates as automakers have pressed the EU to relax CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with large automotive manufacturing.

Several senior officials have proposed plug-in hybrids as a possible “flexibility” option to introduce in the legislation.

One independent energy economics expert, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which segments of the car sector claimed there was too little data to accurately assess real-world emissions.

“The results demonstrate, without question, that the gap between official and real-world PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” the expert said. “Any policy changes regarding PHEVs should be made with extreme care and in the light of that evidence.”