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Plug-in hybrid cars release almost five times greater global warming emissions than lab-reported data indicate, as per a new analysis.

Growing Gap In Lab and Actual Emissions

Data shows that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, based on research conducted by a advocacy organization. That differs sharply with laboratory estimates, which suggested a 75% reduction in emissions.

Researchers examined information from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” stated a senior researcher participating in the report. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Primary Reasons Behind the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in battery mode compared to total distance. The team found that just a quarter of driving was done in EV mode, while lab estimates suggested 84%.

Additionally, when running in electric mode, pollution levels were well above official estimates. That happened because electric motors were insufficiently powerful enough to operate alone, resulting to combustion motors burning gasoline for almost one-third of the travel covered in EV mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled several large automaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

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

“The bold statements that automakers like to make about their PHEV vehicles are clearly way off the mark,” commented a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been brought again into political discussions as automakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with large automotive industries.

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

An external energy economics specialist, who was not involved with the research, described the analysis a “very useful addition” after a long period in which segments of the automotive sector argued there was insufficient information to accurately assess actual CO2 output.

“The results demonstrate, without question, that the gap between official and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel vehicles,” the expert stated. “All policy adjustments concerning PHEVs should be made with utmost care and in the light of this data.”