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PHEVs release almost 5x more planet-heating pollution than lab-reported figures indicate, according to a new report.

Growing Gap In Official and Real-World Emissions

Statistics shows that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel cars, based on research conducted by a non-profit organization. This contrasts sharply with lab estimates, which assumed a three-quarters decrease in emissions.

Researchers studied information from in-vehicle fuel consumption meters of 800,000 vehicles registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” stated a lead researcher participating in the study. “That gap is growing and poses a serious problem. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery power compared to overall mileage. The team determined that only 27% of travel was done in EV mode, while lab assumptions suggested 84%.

Even, when running in EV mode, emission levels were well above lab estimates. That happened because electric motors were not strong sufficient to operate alone, resulting to combustion motors burning gasoline for nearly one-third of the distance completed in EV mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed several large carmaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 extra per year in running costs than is estimated under laboratory tests.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are obviously far from the truth,” commented a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little improved than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Industry Lobbying

Hybrid vehicles have recently been drawn again into political discussions as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with large automotive manufacturing.

Several high-level officials have suggested PHEVs as a potential “flexibility” solution to include in the regulation.

An independent energy policy expert, who was unaffiliated with the study, called the report a “very useful addition” after years in which parts of the automotive industry claimed there was insufficient data to accurately assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap in lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel cars,” they stated. “Any policy changes concerning PHEVs should be implemented with utmost caution and considering that data.”