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Plug-in hybrid cars release nearly 5x more global warming pollution than lab-reported data show, according to a new report.

Widening Discrepancy In Official and Actual CO2 Output

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

Researchers studied data from in-vehicle energy use meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are falling,” said a lead researcher involved in the study. “This gap is widening and creates a significant problem. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in electric mode compared to overall mileage. They found that only a quarter of travel was done in EV mode, while lab estimates suggested over four-fifths.

Even, when running in EV mode, emission amounts were significantly higher than official projections. This happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors using gasoline for nearly one-third of the distance covered in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV emissions enabled four large automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 extra per year in operating expenses than would be estimated under laboratory conditions.

“The bold statements that automakers like to make about their PHEV vehicles are obviously way off the mark,” commented a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Political Discussion and Industry Lobbying

Hybrid cars have recently been drawn again into political debates as carmakers have lobbied the EU to relax CO₂ standards. A proposed ban on new combustion engine cars in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with significant automotive manufacturing.

Several senior officials have proposed PHEVs as a possible “compromise” option to include in the legislation.

An independent energy policy specialist, who was unaffiliated with the research, called the report a “highly valuable contribution” after years in which segments of the car industry claimed there was too little data to properly evaluate actual emissions.

“The results show, without question, that the difference in official and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional cars,” they stated. “Any regulatory changes concerning PHEVs should be made with utmost caution and considering that evidence.”