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Plug-in hybrid electric vehicles release almost five times greater global warming emissions than official figures show, as per a new report.

Widening Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, according to analysis conducted by a non-profit group. This differs significantly with lab estimates, which suggested a 75% decrease in pollution.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” stated a senior analyst involved in the report. “This gap is widening and poses a serious issue. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Primary Factors Behind the Discrepancy

Researchers linked most of the gap to inflated estimates of the “utility factor” – the ratio of miles driven in electric power relative to total mileage. The team determined that only a quarter of travel was completed in electric mode, while lab assumptions suggested 84%.

Even, when operating in EV mode, pollution levels were significantly higher than official projections. That happened because electric motors were not strong enough to operate independently, resulting to engines burning gasoline for almost a third of the distance covered in EV mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions enabled several major automaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay about €500 extra annually in running expenses than would be assumed under lab conditions.

“The strong statements that manufacturers often promote about their PHEV cars are obviously way off the mark,” commented a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Debate and Automotive Pressure

Hybrid cars have lately been drawn again into policy discussions as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced intense pressure from the automotive industry and opposition from member states with significant automotive manufacturing.

Some high-level politicians have suggested PHEVs as a possible “flexibility” solution to introduce in the regulation.

One external energy economics specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which parts of the automotive sector claimed there was insufficient information to accurately assess real-world emissions.

“The results show, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel cars,” they stated. “All regulatory adjustments regarding PHEVs should be implemented with extreme care and considering this evidence.”