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PHEVs release nearly five times more global warming pollution than official data indicate, according to a recent analysis.

Widening Gap In Official and Real-World CO2 Output

Data shows that PHEVs release only 19% less CO₂ than traditional gas and diesel vehicles, based on research carried out by a non-profit group. This differs sharply with laboratory estimates, which assumed a 75% decrease in emissions.

Researchers examined information from onboard fuel consumption monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” said a lead researcher involved in the report. “That discrepancy is widening and creates a significant issue. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in electric power relative to overall distance. The team found that only 27% of driving was completed in electric mode, whereas official estimates suggested 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than official estimates. This happened because EV motors were insufficiently powerful sufficient to function independently, resulting to combustion motors using gasoline for almost a third of the distance covered in electric mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV emissions enabled four large automaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 extra annually in operating expenses than would be assumed under lab tests.

“The strong claims that automakers often promote about their PHEV cars are obviously far from the mark,” stated a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have lately been brought back into policy debates as carmakers have pressed the EU to relax CO₂ targets. A proposed ban on new combustion engine vehicles in 2035 has faced intense pressure from the car industry and opposition from EU countries with large automotive manufacturing.

Some high-level officials have suggested PHEVs as a possible “compromise” option to include in the legislation.

One independent energy policy expert, who was not involved with the research, called the analysis a “highly valuable addition” after years in which parts of the car industry argued there was insufficient information to accurately evaluate real-world CO2 output.

“The results show, without question, that the difference in official and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel vehicles,” the expert stated. “Any policy changes regarding PHEVs should be made with utmost care and in the light of this data.”