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Plug-in hybrid electric vehicles release nearly 5x greater planet-heating pollution than official figures indicate, as per a new report.

Growing Discrepancy Between Official and Real-World CO2 Output

Data reveals that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel cars, according to research conducted by a advocacy organization. This differs sharply with lab tests, which suggested a three-quarters reduction in emissions.

Analysts examined information from in-vehicle energy use monitors of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from three and a half times in 2021.

“Actual emissions are rising, while official figures are falling,” said a senior analyst involved in the report. “This discrepancy is widening and poses a serious issue. Consequently, PHEVs emit nearly as much as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric mode compared to total mileage. The team determined that only a quarter of driving was completed in EV mode, while lab assumptions assumed 84%.

Even, when operating in EV mode, pollution levels were well above lab estimates. This occurred because EV motors were not strong sufficient to operate alone, resulting to engines using fossil fuels for almost one-third of the travel completed in EV mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions enabled several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more per year in operating expenses than would be assumed under laboratory tests.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are obviously way off the truth,” stated a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Political Debate and Industry Lobbying

Hybrid vehicles have recently been brought again into policy debates as automakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on new combustion engine vehicles in 2035 has faced intense pressure from the car sector and resistance from EU countries with significant automotive manufacturing.

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

An independent energy policy specialist, who was unaffiliated with the study, described the report a “very useful contribution” after years in which parts of the automotive sector argued there was insufficient information to accurately evaluate real-world emissions.

“The results show, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional vehicles,” the expert said. “Any regulatory adjustments regarding PHEVs should be made with utmost caution and considering this evidence.”