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Plug-in hybrid electric vehicles produce almost five times greater global warming pollution than official figures show, as per a recent report.

Widening Discrepancy Between Official and Real-World Emissions

Data reveals that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a non-profit organization. That differs significantly with lab estimates, which suggested a 75% decrease in pollution.

Researchers examined information from onboard energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are falling,” said a lead analyst participating in the study. “That discrepancy is widening and creates a serious issue. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to overall distance. They found that only a quarter of driving was done in EV mode, while lab estimates assumed 84%.

Additionally, when operating in EV mode, pollution levels were well above lab estimates. That happened because EV motors were not strong sufficient to function independently, resulting to engines burning gasoline for almost one-third of the distance completed in EV mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output allowed four large carmaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay about €500 extra annually in running costs than is assumed under lab tests.

“The bold statements that automakers often promote about their PHEV vehicles are obviously way off the truth,” commented a automotive expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have lately been brought back into policy discussions as automakers have pressed the European Union to relax CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large automotive manufacturing.

Some senior officials have suggested plug-in hybrids as a possible “compromise” solution to introduce in the regulation.

An external energy policy expert, who was not involved with the study, described the report a “very useful contribution” after years in which parts of the automotive sector argued there was insufficient information to properly assess actual CO2 output.

“The results show, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or conventional vehicles,” the expert said. “Any regulatory adjustments concerning PHEVs should be made with extreme caution and considering that evidence.”