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Plug-in hybrid electric vehicles release nearly five times more global warming emissions than lab-reported figures show, according to a recent report.

Growing Discrepancy Between Official and Real-World Emissions

Statistics reveals that PHEVs release just one-fifth less CO₂ than traditional gas and diesel cars, based on research conducted by a advocacy group. That contrasts significantly with laboratory estimates, which suggested a three-quarters decrease in emissions.

Researchers studied information from onboard energy use meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are decreasing,” said a lead analyst participating in the study. “That discrepancy is widening and creates a serious issue. As a result, PHEVs emit almost as heavily as gasoline cars.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in electric power compared to total distance. The team determined that only a quarter of driving was done in electric mode, whereas lab assumptions suggested 84%.

Additionally, when operating in electric mode, pollution amounts were significantly higher than lab estimates. That happened because electric motors were not strong enough to function independently, resulting to combustion motors burning gasoline for nearly one-third of the distance completed in EV mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output enabled four major automaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra annually in operating costs than would be assumed under lab tests.

“The bold statements that automakers often promote about their PHEV vehicles are obviously far from the mark,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Hybrid cars have recently been drawn again into political discussions as automakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from EU countries with significant automotive manufacturing.

Several senior politicians have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

An independent energy policy expert, who was unaffiliated with the research, called the report a “very useful contribution” after a long period in which segments of the automotive sector claimed there was too little data to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap in official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel cars,” they stated. “All regulatory adjustments concerning PHEVs should be made with extreme caution and in the light of that data.”