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PHEVs emit nearly five times more global warming emissions than official data indicate, according to a recent report.

Widening Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs release just one-fifth less CO₂ than traditional gas and diesel vehicles, based on research carried out by a advocacy organization. This differs sharply with laboratory tests, which suggested a three-quarters decrease in emissions.

Researchers examined data from onboard fuel consumption meters of 800,000 cars registered in the EU from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” stated a senior analyst involved in the study. “This gap is growing and creates a serious problem. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of miles driven in electric power relative to total distance. They found that only a quarter of driving was done in electric mode, whereas official assumptions assumed over four-fifths.

Additionally, when running in EV mode, emission levels were well above official projections. That happened because electric motors were insufficiently powerful sufficient to function independently, leading to engines using fossil fuels for nearly one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV emissions enabled four large automaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could spend approximately €500 extra annually in running expenses than would be estimated under lab tests.

“The bold statements that manufacturers often promote about their PHEV vehicles are clearly way off the truth,” commented a automotive analyst. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating costs.”

Political Debate and Industry Pressure

Hybrid vehicles have recently been brought back into political discussions as automakers have pressed the EU to weaken CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced intense pressure from the car sector and opposition from EU countries with significant automotive manufacturing.

Several senior politicians have suggested plug-in hybrids as a possible “compromise” option to introduce in the regulation.

One independent energy economics specialist, who was not involved with the study, called the analysis a “highly valuable addition” after a long period in which segments of the car sector argued there was too little data to accurately evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel vehicles,” the expert stated. “Any regulatory changes regarding PHEVs should be made with extreme care and considering this evidence.”