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Plug-in hybrid cars produce almost 5x greater planet-heating pollution than official figures indicate, as per a recent report.

Widening Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release just one-fifth lower CO₂ than conventional petrol and diesel cars, based on analysis carried out by a non-profit organization. This contrasts sharply with lab estimates, which suggested a three-quarters decrease in emissions.

Analysts examined information from in-vehicle fuel consumption meters of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are decreasing,” said a lead researcher participating in the report. “That gap is growing and creates a serious problem. As a result, PHEVs emit almost as much as petrol vehicles.”

Key Reasons Driving the Discrepancy

Researchers attributed most of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric mode compared to total mileage. The team found that only a quarter of travel was done in EV mode, whereas official estimates assumed 84%.

Additionally, when running in EV mode, emission levels were well above lab projections. That occurred because EV motors were not strong enough to operate independently, leading to combustion motors burning gasoline for almost one-third of the travel completed in EV mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV CO2 output allowed several major automaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 extra annually in running costs than is assumed under lab tests.

“The bold statements that manufacturers often promote about their PHEV vehicles are obviously far from the truth,” stated a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have recently been brought again into policy discussions as automakers have pressed the European Union to relax CO₂ targets. A proposed ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car industry and opposition from member states with large car industries.

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

An independent energy economics expert, who was not involved with the study, described the report a “very useful addition” after a long period in which parts of the car industry claimed there was too little data to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” the expert said. “All policy adjustments regarding PHEVs should be implemented with extreme caution and considering that data.”