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PHEVs produce almost five times greater planet-heating pollution than lab-reported figures show, according to a new report.

Growing Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, according to research conducted by a non-profit organization. This differs significantly with lab estimates, which suggested a three-quarters reduction in emissions.

Researchers studied information from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a lead researcher involved in the report. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to overall mileage. They found that just 27% of travel was done in EV mode, while official estimates suggested over four-fifths.

Even, when running in EV mode, pollution amounts were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful enough to operate alone, resulting to engines burning fossil fuels for almost one-third of the distance covered in electric mode.

Policy and Financial Implications

Based on calculations, the lowballing of PHEV CO2 output allowed four major carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 extra per year in running costs than would be assumed under lab tests.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the truth,” stated a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Political Discussion and Industry Pressure

Hybrid cars have lately been drawn back into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from EU countries with significant automotive manufacturing.

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

One independent energy policy expert, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the car sector argued there was too little data to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or diesel cars,” the expert stated. “All policy changes concerning PHEVs should be made with extreme care and considering this data.”