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PHEVs release nearly 5x greater planet-heating pollution than official figures show, according to a new report.

Widening Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs emit just one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a non-profit group. That differs significantly with lab tests, which suggested a 75% reduction in emissions.

Analysts studied data from onboard energy use monitors of eight hundred thousand vehicles registered in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are decreasing,” stated a lead analyst participating in the report. “This discrepancy is growing and creates a serious problem. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Behind the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the percentage of miles driven in battery power relative to overall mileage. They found that only a quarter of travel was done in electric mode, while official estimates suggested 84%.

Even, when running in electric mode, pollution levels were well above official projections. That occurred because EV motors were insufficiently powerful sufficient to operate alone, leading to engines burning fossil fuels for almost one-third of the distance covered in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV emissions enabled several large carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 more per year in operating costs than is estimated under lab conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Political Discussion and Industry Lobbying

Hybrid vehicles have recently been brought again into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and resistance from EU countries with significant car manufacturing.

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

One independent energy policy expert, who was not involved with the research, called the analysis a “highly valuable contribution” after a long period in which segments of the car industry argued there was insufficient data to properly evaluate real-world emissions.

“These findings demonstrate, without question, that the gap between official and actual PHEV energy use and CO₂ output is much, much greater than for petrol or conventional vehicles,” the expert stated. “Any policy changes concerning PHEVs should be made with extreme caution and considering this data.”