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Plug-in hybrid cars release almost 5x more global warming emissions than lab-reported data indicate, as per a recent analysis.

Growing Gap In Lab and Actual CO2 Output

Statistics reveals that PHEVs emit just 19% lower CO₂ than conventional gas and diesel vehicles, according to research carried out by a non-profit group. That differs sharply with lab tests, which assumed a three-quarters reduction in pollution.

Analysts examined information from in-vehicle energy use meters of 800,000 vehicles registered in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while official figures are decreasing,” said a senior analyst participating in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to overall distance. The team determined that just a quarter of travel was completed in EV mode, while official assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission amounts were well above official projections. This happened because EV motors were insufficiently powerful sufficient to function independently, leading to combustion motors burning gasoline for nearly a third of the travel completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled several major automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 extra per year in operating expenses than would be assumed under laboratory tests.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are obviously way off the mark,” commented a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into policy debates as carmakers have pressed the EU to relax CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced intense pressure from the car industry and resistance from EU countries with significant automotive industries.

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

An independent energy economics expert, who was not involved with the study, called the report a “highly valuable addition” after years in which segments of the car sector argued there was too little information to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the difference between lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional vehicles,” the expert stated. “All policy adjustments regarding PHEVs should be implemented with extreme caution and in the light of this data.”