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Plug-in hybrid electric vehicles produce nearly five times greater planet-heating emissions than lab-reported figures show, according to a new analysis.

Growing Gap In Lab and Real-World Emissions

Statistics reveals that PHEVs emit only 19% lower CO₂ than conventional gas and diesel cars, based on research conducted by a non-profit group. This differs significantly with lab tests, which suggested a 75% reduction in pollution.

Researchers examined data from onboard fuel consumption meters of eight hundred thousand cars 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 figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” said a lead analyst participating in the study. “That discrepancy is growing and poses a significant problem. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “utility factor” – the percentage of miles driven in electric power compared to total mileage. They found that only 27% of driving was done in electric mode, whereas lab estimates suggested 84%.

Even, when running in electric mode, emission levels were significantly higher than official estimates. That happened because EV motors were not strong sufficient to function independently, leading to combustion motors using gasoline for almost one-third of the travel completed in electric mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV emissions enabled four major carmaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 extra per year in operating costs than is assumed under laboratory conditions.

“The bold claims that automakers like to make about their PHEV cars are clearly way off the mark,” commented a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought again into political discussions as carmakers have pressed the EU to relax CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with large car manufacturing.

Several senior politicians have proposed plug-in hybrids as a possible “flexibility” option to include in the regulation.

One independent energy policy expert, who was not involved with the study, called the analysis a “very useful addition” after a long period in which parts of the car sector claimed there was insufficient information to accurately evaluate actual emissions.

“The results demonstrate, beyond any doubt, that the gap between lab and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel vehicles,” they said. “Any policy changes regarding PHEVs should be made with utmost care and in the light of this evidence.”