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Plug-in hybrid cars emit nearly 5x greater global warming emissions than lab-reported figures show, according to a new report.

Widening Discrepancy In Official and Real-World CO2 Output

Data shows that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel cars, according to analysis conducted by a non-profit organization. That differs significantly with lab tests, which suggested a three-quarters reduction in pollution.

Analysts examined data from in-vehicle fuel consumption meters of 800,000 cars sold in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” stated a lead researcher involved in the study. “That gap is widening and creates a serious issue. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Key Reasons Behind the Discrepancy

Analysts linked most of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in electric mode relative to total distance. The team found that just a quarter of travel was done in EV mode, while lab estimates assumed 84%.

Additionally, when operating in EV mode, pollution amounts were significantly higher than official estimates. This happened because electric motors were not strong sufficient to operate alone, resulting to engines using gasoline for almost a third of the travel covered in EV mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV emissions enabled four large automaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 extra annually in operating expenses than is assumed under lab conditions.

“The strong statements that automakers like to make about their PHEV cars are clearly way off the mark,” stated a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Political Debate and Industry Lobbying

Hybrid vehicles have lately been brought back into policy debates as automakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with large car manufacturing.

Several high-level politicians have proposed plug-in hybrids as a potential “flexibility” option to include in the regulation.

One independent energy policy expert, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after a long period in which segments of the car industry claimed there was too little information to accurately assess actual emissions.

“The results show, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional vehicles,” they said. “Any policy adjustments concerning PHEVs should be implemented with extreme care and in the light of this data.”