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Plug-in hybrid electric vehicles produce nearly five times more global warming emissions than lab-reported figures indicate, according to a new analysis.

Growing Gap Between Lab and Actual CO2 Output

Statistics reveals that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a advocacy group. That contrasts sharply with lab estimates, which suggested a 75% reduction in pollution.

Researchers studied data from onboard energy use monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They discovered 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 CO2 output are rising, while official figures are falling,” said a lead analyst involved in the study. “That discrepancy is widening and creates a significant problem. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Primary Factors Behind the Emissions Gap

Analysts linked most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in battery mode compared to total distance. The team found that only 27% of travel was done in electric mode, whereas lab estimates assumed over four-fifths.

Even, when operating in EV mode, pollution amounts were well above lab estimates. That happened because EV motors were not strong sufficient to operate alone, resulting to combustion motors using gasoline for almost one-third of the distance covered in electric mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV emissions enabled several large carmaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 more per year in operating expenses than is assumed under lab tests.

“The bold claims that automakers like to make about their PHEV vehicles are clearly far from the truth,” commented a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little better than standard petrol and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been drawn again into political discussions as automakers have lobbied the EU to relax CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with large car industries.

Some high-level officials have suggested plug-in hybrids as a potential “flexibility” solution to include in the legislation.

One external energy economics specialist, who was not involved with the study, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive sector argued there was insufficient data to properly evaluate actual CO2 output.

“The results show, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional vehicles,” they stated. “All policy adjustments regarding PHEVs should be implemented with extreme caution and in the light of this data.”