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PHEVs produce nearly five times more global warming pollution than lab-reported data indicate, according to a new report.

Growing Discrepancy Between Lab and Actual Emissions

Statistics shows that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel cars, according to research conducted by a advocacy group. That contrasts significantly with laboratory tests, which suggested a 75% reduction in emissions.

Analysts studied data from in-vehicle fuel consumption meters of 800,000 vehicles registered in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” said a senior researcher involved in the report. “This gap is widening and poses a significant problem. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Primary Factors Behind the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric power relative to total mileage. The team found that just a quarter of travel was done in electric mode, while official estimates assumed 84%.

Even, when running in electric mode, pollution amounts were significantly higher than official estimates. That occurred because EV motors were not strong enough to function independently, resulting to combustion motors using fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four large automaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely easing adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra per year in operating costs than is estimated under laboratory conditions.

“The bold statements that automakers often promote about their PHEV vehicles are obviously far from the truth,” stated a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been brought back into policy debates as automakers have pressed the EU to weaken CO₂ targets. A proposed ban on new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and opposition from member states with significant automotive industries.

Several senior officials have suggested plug-in hybrids as a possible “compromise” option to include in the legislation.

An independent energy policy expert, who was unaffiliated with the study, described the report a “highly valuable contribution” after years in which segments of the automotive sector claimed there was too little data to properly assess real-world CO2 output.

“The results show, without question, that the gap between official and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or diesel cars,” the expert stated. “Any policy adjustments concerning PHEVs should be made with utmost caution and in the light of that data.”