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Plug-in hybrid cars produce nearly 5x greater global warming emissions than lab-reported figures show, according to a new analysis.

Widening Discrepancy In Official and Real-World CO2 Output

Data shows that PHEVs release only one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a non-profit organization. This differs significantly with laboratory tests, which assumed a 75% reduction in emissions.

Analysts examined data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” stated a lead analyst participating in the study. “This gap is widening and creates a serious problem. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Key Factors Driving the Emissions Gap

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in electric power compared to total mileage. The team found that only 27% of travel was done in EV mode, while lab estimates suggested 84%.

Even, when operating in EV mode, pollution levels were well above official projections. That occurred because EV motors were not strong sufficient to operate alone, leading to combustion motors burning gasoline for almost one-third of the travel covered in electric mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV emissions allowed several large carmaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely easing adherence with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 extra annually in operating costs than is assumed under laboratory tests.

“The strong claims that automakers often promote about their PHEV vehicles are obviously way off the truth,” commented a transport analyst. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little improved than regular gas and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been drawn back into political discussions as automakers have pressed the EU to weaken CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with significant car manufacturing.

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

An independent energy economics specialist, who was not involved with the study, called the report a “very useful contribution” after a long period in which segments of the automotive industry claimed there was too little information to properly evaluate actual CO2 output.

“The results demonstrate, without question, that the gap between official and actual PHEV energy use and CO₂ output is much, much larger than for petrol or diesel cars,” the expert said. “All policy changes regarding PHEVs should be implemented with extreme caution and in the light of that evidence.”