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Plug-in hybrid electric vehicles emit nearly five times greater global warming emissions than lab-reported data indicate, according to a new report.

Growing Gap Between Official and Real-World CO2 Output

Data reveals that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel vehicles, according to research conducted by a advocacy group. This contrasts sharply with lab tests, which suggested a 75% decrease in emissions.

Researchers studied data from onboard energy use monitors of 800,000 vehicles sold in the EU between 2021 and 2023. The team found that real-world CO₂ emissions 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 figures are falling,” stated a senior analyst participating in the study. “That gap is growing and creates a serious issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Key Reasons Driving the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric mode compared to overall mileage. They determined that just a quarter of driving was completed in EV mode, while official assumptions assumed over four-fifths.

Even, when running in EV mode, pollution levels were significantly higher than lab projections. That happened because EV motors were insufficiently powerful enough to operate alone, resulting to combustion motors burning gasoline for almost a third of the distance completed in electric mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV emissions allowed several large automaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra annually in running expenses than is estimated under lab tests.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are little improved than standard gas and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Hybrid cars have recently been brought again into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A planned ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car sector and resistance from EU countries with large car manufacturing.

Some senior politicians have proposed PHEVs as a possible “compromise” solution to include in the legislation.

An external energy economics expert, who was unaffiliated with the study, called the report a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was insufficient information to accurately evaluate actual emissions.

“The results show, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel vehicles,” they said. “All policy adjustments regarding PHEVs should be made with utmost care and in the light of this data.”