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Plug-in hybrid electric vehicles produce almost 5x greater planet-heating pollution than official figures show, as per a new analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel cars, based on analysis carried out by a non-profit organization. That contrasts sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles sold in Europe between 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 emissions are increasing, while lab-reported emissions are falling,” stated a senior analyst participating in the study. “That gap is widening and poses a serious problem. As a result, PHEVs emit almost as much as gasoline vehicles.”

Key Factors Behind the Emissions Gap

Researchers linked the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to total mileage. They determined that just 27% of driving was done in EV mode, while official assumptions suggested over four-fifths.

Additionally, when running in electric mode, emission levels were significantly higher than official projections. That happened because electric motors were not strong enough to function independently, resulting to combustion motors burning fossil fuels for nearly one-third of the distance covered in electric mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV CO2 output allowed several large carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 extra per year in operating expenses than would be assumed under lab tests.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Discussion and Automotive Pressure

Hybrid vehicles have lately been brought back into policy debates as carmakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the car industry and opposition from member states with significant car manufacturing.

Several senior politicians have proposed plug-in hybrids as a possible “flexibility” option to include in the legislation.

One external energy economics expert, who was not involved with the study, described the report a “very useful contribution” after a long period in which parts of the car industry argued there was too little information to properly evaluate actual CO2 output.

“The results demonstrate, without question, that the difference between official and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or conventional vehicles,” the expert stated. “All policy changes regarding PHEVs should be implemented with extreme caution and considering that data.”