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Plug-in hybrid electric vehicles produce almost five times more global warming pollution than lab-reported data show, as per a new analysis.

Growing Discrepancy Between Lab and Actual Emissions

Statistics reveals that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, based on analysis conducted by a non-profit group. That contrasts significantly with lab tests, which suggested a 75% reduction in emissions.

Researchers examined data from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” stated a senior analyst participating in the report. “This discrepancy is growing and creates a serious problem. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Reasons Driving the Discrepancy

Researchers linked most of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to overall distance. They determined that only a quarter of travel was done in EV mode, while lab assumptions assumed 84%.

Even, when operating in EV mode, pollution amounts were significantly higher than lab estimates. That occurred because electric motors were not strong enough to operate independently, leading to combustion motors burning gasoline for nearly one-third of the travel completed in EV mode.

Policy and Financial Implications

According to calculations, the underestimation of PHEV CO2 output allowed four major carmaker companies to escape over €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

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

“The strong claims that manufacturers like to make about their plug-in hybrid cars are clearly way off the truth,” stated a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than standard gas and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn back into policy discussions as carmakers have lobbied the European Union to relax CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large car industries.

Some senior officials have proposed PHEVs as a potential “flexibility” solution to include in the regulation.

An external 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 argued there was too little information to properly assess real-world emissions.

“These findings show, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel cars,” the expert stated. “All policy changes regarding PHEVs should be made with utmost caution and in the light of this evidence.”