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Plug-in hybrid electric vehicles produce nearly 5x greater global warming pollution than lab-reported data show, as per a recent analysis.

Widening Gap In Lab and Real-World CO2 Output

Data reveals that PHEVs emit only one-fifth lower CO₂ than conventional gas and diesel vehicles, based on research conducted by a non-profit group. This contrasts sharply with lab estimates, which suggested a three-quarters reduction in emissions.

Researchers studied information from onboard fuel consumption meters of 800,000 vehicles sold in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are falling,” said a senior researcher involved in the study. “That discrepancy is growing and creates a serious problem. Consequently, PHEVs pollute almost as much as petrol cars.”

Primary Factors Behind the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of miles driven in electric mode relative to total mileage. They found that only a quarter of driving was completed in EV mode, whereas lab assumptions suggested 84%.

Even, when operating in electric mode, emission amounts were significantly higher than lab projections. This happened because EV motors were not strong sufficient to function alone, leading to combustion motors using gasoline for nearly one-third of the distance completed in electric mode.

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV emissions allowed several large carmaker companies to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

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

“The bold statements that automakers often promote about their plug-in hybrid vehicles are clearly way off the mark,” stated a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Political Discussion and Industry Lobbying

Hybrid vehicles have lately been brought back into policy discussions as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced intense pressure from the car sector and opposition from member states with large automotive manufacturing.

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

One independent energy policy expert, who was not involved with the research, described the report a “very useful contribution” after a long period in which segments of the automotive sector argued there was too little information to accurately assess actual CO2 output.

“These findings demonstrate, without question, that the gap between official and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional cars,” the expert stated. “Any regulatory changes concerning PHEVs should be made with extreme care and considering that evidence.”