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Plug-in hybrid electric vehicles emit almost five times greater global warming emissions than official figures indicate, according to a recent report.

Growing Gap In Lab and Actual CO2 Output

Data shows that PHEVs release just one-fifth less CO₂ than traditional petrol and diesel cars, based on research conducted by a advocacy group. That differs significantly with lab tests, which suggested a three-quarters decrease in emissions.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” stated a senior researcher involved in the report. “That discrepancy is growing and creates a significant problem. Consequently, PHEVs emit almost as much as petrol cars.”

Key Factors Behind the Discrepancy

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric power compared to total distance. The team found that only a quarter of travel was done in electric mode, while lab assumptions assumed 84%.

Additionally, when operating in EV mode, pollution amounts were well above official estimates. This happened because EV motors were not strong sufficient to operate independently, resulting to engines using fossil fuels for almost one-third of the distance covered in EV mode.

Policy and Financial Implications

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

Additionally, owners of PHEVs would pay about €500 extra per year in operating expenses than would be assumed under laboratory conditions.

“The bold statements that automakers often promote about their plug-in hybrid cars are clearly way off the truth,” stated a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have lately 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 heavy lobbying from the car industry and resistance from EU countries with significant automotive manufacturing.

Some senior officials have proposed PHEVs as a possible “flexibility” solution to include in the regulation.

One external energy policy specialist, who was unaffiliated with the study, called the report a “very useful addition” after years in which segments of the automotive sector argued there was too little data to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or conventional cars,” they said. “All policy adjustments regarding PHEVs should be implemented with extreme caution and in the light of that data.”