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Plug-in hybrid cars produce nearly five times greater global warming pollution than official data indicate, according to a new analysis.

Widening Discrepancy In Official and Actual Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, according to research conducted by a advocacy organization. That differs significantly with laboratory estimates, which assumed a 75% decrease in emissions.

Analysts studied information from in-vehicle energy use meters of 800,000 vehicles sold in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” said a lead analyst participating in the study. “That discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Primary Factors Driving the Discrepancy

Researchers linked most of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in battery mode relative to total mileage. The team found that just a quarter of driving was done in EV mode, whereas lab assumptions assumed 84%.

Additionally, when operating in EV mode, pollution levels were well above lab projections. That happened because electric motors were not strong enough to function independently, resulting to combustion motors burning gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed several major carmaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 more annually in running expenses than would be estimated under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” commented a transport analyst. “Buyers are being misled into thinking 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 use, CO₂ production, and operating expenses.”

Political Discussion and Automotive Pressure

Hybrid cars have lately been brought back into policy debates as automakers have lobbied the EU to weaken CO₂ targets. A proposed ban on new combustion engine cars in 2035 has faced heavy lobbying from the car sector and opposition from member states with large car industries.

Several senior politicians have suggested plug-in hybrids as a possible “compromise” option to include in the legislation.

An external energy policy expert, who was unaffiliated with the study, called the report a “very useful contribution” after a long period in which segments of the car sector claimed there was too little information to accurately assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the difference in lab 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 made with utmost caution and in the light of that data.”