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Plug-in hybrid electric vehicles produce nearly five times greater global warming emissions than official figures indicate, according to a new report.

Growing Discrepancy In Official and Actual CO2 Output

Data reveals that PHEVs release just 19% less CO₂ than conventional gas and diesel cars, based on research conducted by a advocacy group. That differs sharply with lab estimates, which assumed a three-quarters decrease in emissions.

Researchers examined data from in-vehicle energy use monitors of 800,000 vehicles sold 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.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” stated a lead analyst involved in the study. “This gap is growing and creates a significant issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Key Reasons Behind the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in electric power compared to overall distance. They determined that only a quarter of travel was completed in EV mode, while lab estimates suggested 84%.

Even, when operating in electric mode, pollution levels were well above lab estimates. That happened because EV motors were not strong enough to operate alone, leading to combustion motors using gasoline for nearly a third of the travel covered in EV mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled four major carmaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 more per year in operating costs than would be assumed under lab tests.

“The bold claims that manufacturers often promote about their PHEV cars are clearly way off the truth,” stated a automotive analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are little better than standard gas and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been brought again into policy debates as carmakers have lobbied the EU to relax CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from member states with large automotive industries.

Several high-level officials have suggested PHEVs as a possible “flexibility” option to include in the regulation.

An independent energy policy expert, who was not involved with the research, called the report a “highly valuable addition” after years in which segments of the automotive industry argued there was too little information to accurately assess real-world emissions.

“The results show, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert said. “All regulatory adjustments regarding PHEVs should be made with extreme caution and considering that evidence.”