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Plug-in hybrid electric vehicles produce almost five times more global warming pollution than official data indicate, according to a new report.

Growing Gap In Lab and Actual CO2 Output

Statistics shows that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a advocacy group. That differs sharply with lab tests, which assumed a three-quarters decrease in emissions.

Researchers studied data from onboard energy use meters of eight hundred thousand vehicles registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a lead researcher involved in the report. “This discrepancy is growing and creates a serious problem. As a result, PHEVs pollute almost as much as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to total mileage. The team determined that only a quarter of driving was completed in EV mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution levels were well above official projections. That happened because EV motors were not strong enough to function independently, resulting to combustion motors using gasoline for nearly one-third of the distance completed in EV mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV CO2 output allowed several major automaker groups to escape over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay approximately €500 more annually in operating costs than would be estimated under laboratory tests.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the truth,” commented a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been brought again into political discussions as automakers have pressed the EU to weaken CO₂ targets. A planned ban on new internal combustion cars in 2035 has faced intense pressure from the car industry and resistance from member states with large car industries.

Several senior officials have proposed PHEVs as a possible “flexibility” option to introduce in the legislation.

An external energy policy expert, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which parts of the automotive industry claimed there was too little information to accurately assess real-world CO2 output.

“The results show, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional cars,” they said. “All regulatory changes concerning PHEVs should be implemented with utmost care and considering this data.”