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Plug-in hybrid cars release almost 5x greater global warming pollution than lab-reported data indicate, according to a new report.

Widening Gap In Official and Real-World Emissions

Data reveals that PHEVs release just 19% less CO₂ than traditional gas and diesel cars, based on research carried out by a advocacy organization. That differs significantly with lab tests, which suggested a three-quarters reduction in emissions.

Researchers studied data from in-vehicle fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” stated a lead researcher participating in the study. “That gap is widening and creates a serious problem. As a result, PHEVs emit nearly as heavily as petrol cars.”

Key Factors Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to overall mileage. The team determined that only 27% of driving was completed in EV mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, emission levels were significantly higher than official projections. That occurred because electric motors were not strong sufficient to operate independently, resulting to combustion motors using gasoline for almost a third of the travel covered in EV mode.

Regulatory and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output enabled four large carmaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 extra annually in running expenses than would be assumed under laboratory tests.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” commented a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving costs. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have recently been brought again into policy debates as carmakers have pressed the EU to relax CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with significant automotive manufacturing.

Some senior officials have proposed PHEVs as a potential “compromise” option to introduce in the regulation.

An independent energy economics expert, who was not involved with the study, described the report a “very useful contribution” after years in which parts of the car sector argued there was insufficient data to properly assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between lab and actual PHEV energy use and CO₂ output is significantly larger than for petrol or diesel cars,” they stated. “Any policy changes concerning PHEVs should be implemented with utmost care and in the light of this evidence.”