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Plug-in hybrid electric vehicles emit almost five times greater planet-heating pollution than official figures show, as per a new report.

Growing Discrepancy Between Official and Actual Emissions

Statistics reveals that PHEVs emit only one-fifth lower CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a advocacy group. This contrasts significantly with lab tests, which suggested a 75% decrease in emissions.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” said a lead analyst participating in the study. “This discrepancy is widening and creates a serious problem. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of miles travelled in battery mode relative to total distance. The team determined that just a quarter of driving was completed in EV mode, whereas official estimates suggested 84%.

Additionally, when operating in EV mode, emission levels were significantly higher than lab estimates. This occurred because electric motors were insufficiently powerful enough to operate alone, resulting to combustion motors burning fossil fuels for almost a third of the travel covered in EV mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled four major automaker companies to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 extra per year in running expenses than would be estimated under laboratory conditions.

“The strong claims that manufacturers often promote about their PHEV cars are obviously way off the mark,” stated a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Political Discussion and Industry Pressure

Hybrid cars have recently been brought again into political debates as automakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the car sector and opposition from member states with significant car manufacturing.

Some senior politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

One independent energy economics specialist, who was not involved with the study, called the analysis a “very useful contribution” after a long period in which segments of the car sector argued there was too little information to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” the expert said. “Any policy adjustments regarding PHEVs should be implemented with utmost caution and in the light of this data.”