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PHEVs produce nearly 5x more global warming pollution than lab-reported data indicate, according to a recent report.

Widening Discrepancy Between Lab and Actual Emissions

Data reveals that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel cars, based on research carried out by a non-profit organization. That contrasts significantly with laboratory estimates, which assumed a 75% reduction in pollution.

Researchers examined data from in-vehicle energy use monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” said a lead researcher involved in the report. “This gap is growing and creates a significant issue. Consequently, PHEVs emit almost as much as petrol vehicles.”

Key Factors Driving the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric mode compared to overall distance. They found that only a quarter of driving was completed in EV mode, while lab assumptions suggested over four-fifths.

Additionally, when operating in electric mode, emission amounts were significantly higher than official estimates. This occurred because EV motors were not strong enough to function alone, leading to engines using gasoline for nearly a third of the travel completed in EV mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output allowed several large automaker companies to escape over €5bn in fines between 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ targets.

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

“The strong statements that automakers like to make about their plug-in hybrid cars are clearly far from the mark,” commented a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Political Debate and Industry Lobbying

Hybrid vehicles have recently been drawn back into political debates as automakers have lobbied the European Union to relax CO₂ targets. A planned ban on new internal combustion cars in 2035 has faced intense pressure from the car sector and opposition from member states with large automotive manufacturing.

Several high-level officials have suggested PHEVs as a possible “compromise” option to introduce in the legislation.

An independent energy economics specialist, who was not involved with the study, described the report a “very useful contribution” after a long period in which segments of the automotive industry claimed there was too little information to accurately evaluate real-world emissions.

“The results demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert said. “All regulatory changes concerning PHEVs should be made with utmost care and considering that data.”