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Plug-in hybrid cars emit almost five times greater global warming pollution than official data indicate, according to a new analysis.

Growing Gap In Lab and Actual Emissions

Data shows that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a advocacy organization. That differs significantly with lab estimates, which suggested a 75% decrease in emissions.

Researchers examined data from in-vehicle energy use monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” stated a senior researcher involved in the report. “That discrepancy is growing and poses a serious problem. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery mode relative to total distance. They determined that only 27% of driving was completed in EV mode, while official estimates assumed over four-fifths.

Even, when operating in EV mode, emission levels were significantly higher than official projections. That occurred because electric motors were not strong sufficient to operate alone, resulting to combustion motors burning gasoline for nearly a third of the travel covered in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed several large carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would spend about €500 more annually in operating costs than would be estimated under laboratory tests.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the mark,” commented a automotive expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Hybrid vehicles have recently been drawn again into political debates as carmakers have pressed the EU to weaken CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and opposition from member states with significant car manufacturing.

Several high-level politicians have suggested PHEVs as a possible “flexibility” solution to introduce in the regulation.

One external energy policy expert, who was not involved with the study, called the analysis a “very useful contribution” after years in which segments of the automotive sector claimed there was insufficient data to properly assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel vehicles,” they said. “Any regulatory adjustments concerning PHEVs should be made with utmost caution and considering that evidence.”