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Plug-in hybrid cars produce nearly five times more planet-heating pollution than official figures indicate, as per a new report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs release only 19% less CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a advocacy group. This differs significantly with lab tests, which suggested a three-quarters reduction in pollution.

Analysts studied information from onboard fuel consumption meters of eight hundred thousand cars registered in the EU between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” said a senior analyst involved in the report. “That gap is growing and poses a significant issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to overall distance. They found that only 27% of driving was completed in electric mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than lab estimates. This happened because EV motors were not strong enough to operate independently, leading to combustion motors using fossil fuels for almost a third of the travel covered in EV mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV CO2 output allowed several large carmaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 more annually in running costs than would be assumed under lab tests.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the mark,” commented a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and running expenses.”

Political Discussion and Automotive Pressure

Hybrid cars have recently been drawn back into policy discussions as carmakers have lobbied the EU to weaken CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and resistance from member states with significant car manufacturing.

Some senior politicians have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

An independent energy policy specialist, who was unaffiliated with the study, called the report a “very useful addition” after a long period in which parts of the car industry claimed there was insufficient information to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference between official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or diesel vehicles,” they stated. “Any policy adjustments regarding PHEVs should be implemented with utmost care and considering that data.”