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Plug-in hybrid cars release nearly 5x greater global warming emissions than lab-reported figures indicate, as per a new report.

Widening Discrepancy In Official and Real-World Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel vehicles, according to research conducted by a advocacy organization. That contrasts sharply with lab tests, which assumed a 75% decrease in pollution.

Researchers examined data from onboard energy use monitors of 800,000 cars sold in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while official figures are falling,” said a senior researcher involved in the study. “This discrepancy is growing and creates a significant problem. Consequently, PHEVs emit almost as much as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in battery power relative to overall distance. They determined that just a quarter of driving was done in electric mode, whereas lab assumptions assumed 84%.

Additionally, when running in electric mode, emission amounts were significantly higher than official estimates. That occurred because electric motors were not strong sufficient to operate independently, resulting to combustion motors burning gasoline for almost one-third of the distance covered in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output enabled four large automaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra annually in running expenses than is assumed under laboratory tests.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are clearly way off the truth,” stated a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of energy use, CO₂ production, and operating costs.”

Policy Discussion and Industry Lobbying

Hybrid cars have recently been drawn again into policy debates as carmakers have pressed the European Union to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from member states with large automotive industries.

Several senior officials have proposed PHEVs as a possible “flexibility” option to introduce in the regulation.

One independent energy economics specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after years in which parts of the automotive industry argued there was insufficient data to accurately evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the gap in official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or diesel vehicles,” they said. “Any policy adjustments concerning PHEVs should be implemented with extreme caution and in the light of this data.”