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Plug-in hybrid electric vehicles produce nearly five times more planet-heating emissions than lab-reported data show, according to a recent report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel vehicles, based on analysis conducted by a non-profit organization. That contrasts sharply with laboratory estimates, which suggested a three-quarters reduction in pollution.

Analysts examined information from in-vehicle energy use meters of eight hundred thousand cars sold in Europe from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a senior researcher participating in the study. “This discrepancy is growing and creates a significant issue. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Researchers attributed most of the difference to overestimates of the “utility factor” – the ratio of kilometers driven in battery mode compared to total mileage. They found that only a quarter of travel was done in electric mode, while official estimates suggested over four-fifths.

Even, when operating in EV mode, emission levels were well above lab projections. This happened because EV motors were insufficiently powerful sufficient to operate independently, resulting to engines burning gasoline for nearly one-third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV emissions enabled several large carmaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra annually in running expenses than is estimated under laboratory conditions.

“The bold claims that manufacturers like to make about their PHEV vehicles are clearly far from the mark,” stated a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and opposition from member states with large automotive manufacturing.

Some senior officials have proposed plug-in hybrids as a potential “compromise” option to include in the legislation.

An external energy policy specialist, who was unaffiliated with the study, called the analysis a “highly valuable addition” after years in which parts of the car sector argued there was too little data to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the gap in official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional cars,” they said. “All regulatory changes concerning PHEVs should be made with utmost caution and in the light of this evidence.”