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Plug-in hybrid electric vehicles produce almost 5x greater planet-heating emissions than lab-reported figures indicate, according to a new report.

Growing Discrepancy In Official and Real-World Emissions

Statistics reveals that PHEVs emit only 19% lower CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit group. This differs significantly with lab tests, which assumed a 75% reduction in emissions.

Researchers examined information from onboard fuel consumption meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” said a senior analyst involved in the report. “That gap is widening and creates a serious issue. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “electric driving share” – the ratio of miles travelled in battery mode compared to total mileage. The team found that just a quarter of travel was completed in electric mode, while lab estimates suggested 84%.

Additionally, when operating in electric mode, emission levels were significantly higher than lab projections. This happened because EV motors were not strong sufficient to function alone, leading to combustion motors burning fossil fuels for nearly a third of the travel covered in electric mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV emissions allowed several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 more annually in operating expenses than is estimated under laboratory tests.

“The bold statements that automakers often promote about their plug-in hybrid cars are obviously far from the mark,” commented a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into policy discussions as carmakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the car sector and resistance from member states with large automotive manufacturing.

Some high-level officials have suggested plug-in hybrids as a possible “compromise” option to introduce in the legislation.

One external energy policy expert, who was not involved with the study, called the analysis a “very useful contribution” after a long period in which segments of the car industry claimed there was too little data to accurately evaluate real-world emissions.

“These findings show, beyond any doubt, that the gap in official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel cars,” the expert stated. “Any policy changes regarding PHEVs should be made with utmost care and in the light of that data.”