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PHEVs release nearly 5x more global warming pollution than official data show, according to a new report.

Growing Discrepancy In Official and Real-World CO2 Output

Statistics shows that PHEVs release only 19% less CO₂ than traditional petrol and diesel cars, according to analysis conducted by a advocacy group. That differs significantly with laboratory tests, which suggested a three-quarters reduction in pollution.

Analysts studied data from onboard fuel consumption meters of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a senior researcher involved in the report. “This discrepancy is widening and poses a serious issue. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Factors Driving the Emissions Gap

Analysts linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery power compared to total mileage. They found that only 27% of travel was completed in electric mode, whereas lab estimates suggested over four-fifths.

Additionally, when running in electric mode, emission amounts were well above official projections. This happened because EV motors were not strong enough to operate independently, resulting to engines burning gasoline for nearly one-third of the distance covered in EV mode.

Policy and Financial Implications

Based on calculations, the underestimation of PHEV emissions enabled several major automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 extra annually in running costs than is estimated under laboratory conditions.

“The bold statements that automakers often promote about their plug-in hybrid cars are obviously way off the mark,” stated a automotive analyst. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been brought again into policy discussions as carmakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced heavy pressure from the car industry and resistance from member states with significant automotive industries.

Several senior officials have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

One independent energy economics specialist, who was not involved with the research, called the report a “highly valuable addition” after years in which segments of the automotive sector argued there was insufficient data to properly assess actual emissions.

“The results demonstrate, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional cars,” the expert stated. “Any policy changes concerning PHEVs should be implemented with utmost care and in the light of that data.”