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Plug-in hybrid cars produce nearly five times more planet-heating emissions than official figures indicate, as per a new report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs release just 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a non-profit group. That contrasts significantly with laboratory estimates, which assumed a three-quarters reduction in emissions.

Analysts examined data from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” stated a senior analyst participating in the study. “That discrepancy is growing and poses a serious problem. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to total mileage. They found that only a quarter of driving was done in electric mode, whereas official estimates suggested 84%.

Additionally, when running in EV mode, emission amounts were significantly higher than lab estimates. That occurred because electric motors were insufficiently powerful sufficient to operate independently, leading to engines using gasoline for nearly a third of the travel completed in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output enabled four large automaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would spend about €500 more per year in operating expenses than is estimated under laboratory conditions.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are obviously way off the truth,” stated a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Pressure

Hybrid vehicles have recently been drawn again into policy discussions as carmakers have pressed the European Union to relax CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced intense lobbying from the car sector and resistance from member states with large automotive manufacturing.

Several high-level politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

An independent energy policy specialist, who was not involved with the research, called the report a “highly valuable addition” after years in which parts of the automotive industry claimed there was too little data to accurately assess actual CO2 output.

“The results show, without question, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” they stated. “Any policy adjustments concerning PHEVs should be made with utmost caution and considering this evidence.”