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PHEVs produce almost five times greater planet-heating emissions than lab-reported data indicate, according to a new report.

Growing Discrepancy Between Official and Actual Emissions

Data shows that PHEVs release just one-fifth less CO₂ than traditional gas and diesel vehicles, according to research carried out by a advocacy group. This differs significantly with laboratory tests, which suggested a 75% decrease in emissions.

Analysts studied information from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” said a senior researcher participating in the study. “That gap is widening and creates a significant problem. As a result, PHEVs emit almost as much as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of miles driven in battery power relative to total mileage. They found that just 27% of driving was done in EV mode, while official estimates suggested 84%.

Even, when running in EV mode, pollution amounts were significantly higher than lab estimates. This happened because electric motors were insufficiently powerful enough to function independently, resulting to combustion motors burning fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Economic Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed several large automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 extra per year in running costs than is assumed under laboratory tests.

“The bold statements that automakers often promote about their PHEV vehicles are obviously far from the truth,” stated a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn back into political discussions as carmakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from member states with large automotive manufacturing.

Some high-level officials have suggested plug-in hybrids as a potential “compromise” option to introduce in the regulation.

An independent energy economics expert, who was unaffiliated with the study, called the analysis a “highly valuable addition” after a long period in which segments of the car industry argued there was too little information to accurately evaluate real-world CO2 output.

“The results show, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ emissions is significantly greater than for gasoline or diesel vehicles,” the expert stated. “All policy adjustments regarding PHEVs should be implemented with utmost care and considering that evidence.”