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Plug-in hybrid cars release nearly five times more global warming emissions than official data indicate, according to a new analysis.

Widening Discrepancy In Lab and Actual CO2 Output

Data shows that PHEVs release just 19% lower CO₂ than traditional gas and diesel cars, based on analysis conducted by a non-profit organization. This contrasts significantly with lab estimates, which suggested a three-quarters reduction in pollution.

Researchers studied data from onboard energy use monitors of 800,000 vehicles registered in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official figures are falling,” said a senior analyst involved in the report. “This discrepancy is growing and creates a serious problem. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Key Factors Behind the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in electric mode relative to overall distance. They determined that only a quarter of driving was completed in electric mode, whereas lab assumptions suggested 84%.

Additionally, when running in EV mode, pollution levels were well above official projections. That happened because electric motors were not strong sufficient to function alone, resulting to engines using gasoline for almost one-third of the travel covered in EV mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV emissions enabled four large automaker companies to escape over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

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

“The bold claims that manufacturers often promote about their PHEV vehicles are obviously far from the truth,” stated a transport expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of fuel use, CO₂ production, and operating expenses.”

Political Discussion and Industry Pressure

Hybrid vehicles have lately been drawn back into political debates as carmakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car sector and resistance from EU countries with large car industries.

Several senior officials have suggested plug-in hybrids as a potential “compromise” solution to include in the legislation.

One independent energy policy specialist, who was unaffiliated with the study, described the analysis a “highly valuable contribution” after years in which segments of the car industry claimed there was too little information to accurately assess actual CO2 output.

“These findings show, without question, that the gap in official and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or conventional cars,” the expert said. “All regulatory adjustments regarding PHEVs should be implemented with extreme caution and considering this data.”