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PHEVs emit nearly five times more global warming pollution than official data indicate, according to a recent analysis.

Growing Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs emit only 19% less CO₂ than traditional gas and diesel cars, based on analysis conducted by a advocacy group. This contrasts sharply with lab tests, which suggested a three-quarters decrease in emissions.

Researchers studied information from onboard fuel consumption monitors of 800,000 vehicles registered in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, up from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” said a lead analyst involved in the report. “That discrepancy is widening and creates a significant issue. Consequently, PHEVs emit nearly as much as gasoline cars.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in electric mode compared to total distance. They found that just a quarter of travel was done in electric mode, while lab estimates assumed 84%.

Additionally, when running in EV mode, emission levels were significantly higher than official projections. This happened because electric motors were not strong enough to function alone, resulting to engines burning gasoline for almost one-third of the travel completed in electric mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV emissions enabled four major automaker companies to escape over €5bn in penalties from 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 extra annually in running costs than would be estimated under laboratory tests.

“The strong claims that manufacturers like to make about their PHEV vehicles are obviously way off the truth,” commented a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been drawn back into policy debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the car sector and resistance from EU countries with significant automotive manufacturing.

Several high-level officials have suggested PHEVs as a possible “flexibility” option to introduce in the legislation.

An external energy economics expert, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive sector argued there was insufficient information to accurately assess real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or diesel cars,” the expert stated. “Any policy adjustments concerning PHEVs should be implemented with utmost care and in the light of that data.”