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Plug-in hybrid electric vehicles produce nearly five times more global warming emissions than official data show, as per a new analysis.

Growing Gap In Official and Actual CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel vehicles, according to research carried out by a non-profit organization. This contrasts significantly with lab tests, which suggested a three-quarters decrease in pollution.

Researchers examined data from in-vehicle energy use monitors of 800,000 vehicles registered in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” stated a lead analyst participating in the study. “That discrepancy is widening and poses a significant issue. Consequently, PHEVs emit almost as much as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to total mileage. The team found that only a quarter of travel was done in electric mode, while lab assumptions assumed over four-fifths.

Even, when operating in EV mode, emission levels were well above official estimates. That happened because EV motors were not strong enough to operate independently, resulting to combustion motors using gasoline for almost a third of the distance completed in electric mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV emissions allowed several large carmaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend approximately €500 more annually in running costs than is assumed under laboratory conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are clearly way off the mark,” commented a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought again into policy debates as automakers have pressed the European Union to relax CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with significant car industries.

Several high-level officials have proposed plug-in hybrids as a potential “flexibility” option to include in the regulation.

An external energy economics specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which segments of the automotive industry argued there was too little information to accurately evaluate actual CO2 output.

“These findings show, without question, that the gap in 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 concerning PHEVs should be implemented with utmost caution and considering this evidence.”