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PHEVs produce nearly 5x greater global warming pollution than lab-reported data show, according to a new analysis.

Growing Gap In Official and Real-World Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than traditional petrol and diesel vehicles, based on research conducted by a non-profit group. That contrasts sharply with laboratory estimates, which assumed a 75% reduction in emissions.

Analysts examined data from onboard fuel consumption monitors of 800,000 vehicles registered in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” said a lead analyst involved in the study. “This discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute almost as much as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers linked most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric mode relative to total distance. The team determined that just 27% of travel was completed in EV mode, whereas lab estimates assumed over four-fifths.

Even, when running in EV mode, pollution levels were well above official estimates. This happened because electric motors were not strong sufficient to operate independently, resulting to combustion motors using gasoline for almost one-third of the distance completed in electric mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV emissions enabled four major carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could pay about €500 more annually in running costs than is estimated under lab conditions.

“The strong claims that manufacturers like to make about their PHEV vehicles are obviously way off the truth,” stated a automotive analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Lobbying

Hybrid vehicles have recently been drawn again into political discussions as carmakers have pressed the EU to relax CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with large car industries.

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

An independent energy economics specialist, who was not involved with the study, called the report a “very useful addition” after years in which segments of the car sector claimed there was insufficient data to accurately evaluate real-world CO2 output.

“The results show, without question, that the difference in official and real-world PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert said. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of this data.”