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Plug-in hybrid cars release almost five times greater global warming emissions than lab-reported figures show, as per a new report.

Widening Gap In Lab and Actual CO2 Output

Statistics reveals that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit organization. This differs sharply with lab tests, which suggested a three-quarters reduction in emissions.

Researchers studied information from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in Europe from 2021 and 2023. They found that actual 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 emissions are rising, while lab-reported figures are decreasing,” said a senior analyst participating in the study. “This gap is growing and creates a serious issue. Consequently, PHEVs emit almost as much as gasoline cars.”

Primary Factors Behind the Discrepancy

Analysts linked the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in battery mode relative to total distance. The team found that only a quarter of travel was done in electric mode, while official assumptions assumed over four-fifths.

Even, when running in electric mode, emission levels were significantly higher than lab estimates. That occurred because EV motors were insufficiently powerful sufficient to operate independently, leading to combustion motors burning gasoline for nearly one-third of the travel covered in electric mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV emissions enabled four large carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 extra per year in running expenses than would be estimated under laboratory tests.

“The strong statements that automakers like to make about their PHEV vehicles are clearly far from the truth,” commented a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been brought back into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with large automotive industries.

Some senior officials have proposed plug-in hybrids as a potential “flexibility” solution to include in the regulation.

One external energy economics specialist, who was not involved with the research, called the analysis a “very useful contribution” after a long period in which parts of the car sector claimed there was too little data to accurately evaluate real-world CO2 output.

“The results show, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” the expert said. “Any regulatory adjustments concerning PHEVs should be made with extreme caution and considering that evidence.”