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Plug-in hybrid cars release nearly five times greater planet-heating pollution than official figures indicate, according to a recent analysis.

Widening Gap Between Official and Real-World Emissions

Statistics reveals that PHEVs release only 19% lower CO₂ than conventional gas and diesel vehicles, based on research carried out by a non-profit group. This contrasts sharply with lab tests, which assumed a three-quarters decrease in pollution.

Analysts examined information from in-vehicle fuel consumption meters of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” said a senior researcher participating in the report. “This discrepancy is widening and poses a serious problem. As a result, PHEVs emit almost as heavily as petrol cars.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric mode relative to overall mileage. The team found that only a quarter of travel was done in electric mode, whereas official estimates assumed over four-fifths.

Even, when running in EV mode, pollution amounts were well above official projections. That happened because electric motors were not strong sufficient to operate alone, resulting to combustion motors using fossil fuels for nearly one-third of the distance covered in electric mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output enabled four large carmaker companies to escape over €5bn in penalties from 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 extra per year in operating expenses than would be assumed under lab conditions.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” stated a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Debate and Automotive Lobbying

Hybrid cars have recently been brought again into policy discussions as automakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large car manufacturing.

Some senior politicians have proposed PHEVs as a potential “flexibility” option to introduce in the regulation.

An independent energy policy expert, who was unaffiliated with the study, called the report a “highly valuable contribution” after a long period in which segments of the automotive sector argued there was insufficient information to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the difference in lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional cars,” the expert said. “All policy adjustments regarding PHEVs should be implemented with extreme caution and in the light of this data.”