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PHEVs release nearly five times greater planet-heating pollution than lab-reported data show, according to a new report.

Growing Gap In Lab and Real-World CO2 Output

Data shows that PHEVs release just 19% lower CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a advocacy group. This contrasts sharply with laboratory estimates, which suggested a three-quarters decrease in pollution.

Researchers examined data from onboard fuel consumption monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” stated a senior analyst participating in the report. “This discrepancy is widening and poses a significant problem. As a result, PHEVs emit almost as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of miles driven in battery mode relative to overall mileage. The team determined that just a quarter of driving was done in EV mode, whereas official estimates assumed 84%.

Additionally, when operating in electric mode, emission levels were significantly higher than lab projections. This happened because electric motors were insufficiently powerful sufficient to function alone, leading to engines using gasoline for nearly a third of the distance completed in electric mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV emissions allowed four major carmaker groups to avoid more than €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 extra per year in running expenses than would be estimated under lab conditions.

“The bold statements that automakers like to make about their plug-in hybrid cars are clearly way off the mark,” stated a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been brought back into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with large automotive manufacturing.

Some senior politicians have proposed plug-in hybrids as a potential “compromise” solution to include in the regulation.

An independent energy policy specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which segments of the automotive sector claimed there was too little information to accurately assess actual emissions.

“The results show, without question, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional cars,” the expert stated. “Any policy adjustments regarding PHEVs should be made with extreme caution and in the light of this evidence.”