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Plug-in hybrid cars emit nearly five times greater global warming emissions than official data show, according to a recent analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy group. That contrasts significantly with laboratory tests, which assumed a three-quarters reduction in pollution.

Analysts examined information from onboard fuel consumption monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a senior analyst participating in the study. “This gap is growing and creates a significant problem. Consequently, PHEVs emit almost as heavily as petrol cars.”

Key Reasons Behind the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the percentage of miles driven in battery mode compared to overall mileage. They found that only a quarter of travel was done in electric mode, while official estimates assumed 84%.

Even, when running in EV mode, emission levels were well above official estimates. That occurred because electric motors were insufficiently powerful enough to operate independently, leading to engines burning gasoline for almost a third of the distance covered in electric mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV emissions allowed four major automaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 more annually in operating costs than would be estimated under lab tests.

“The bold claims that automakers often promote about their PHEV vehicles are obviously far from the truth,” stated a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Hybrid vehicles have recently been brought again into political discussions as automakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the car sector and resistance from member states with large car industries.

Some senior politicians have suggested plug-in hybrids as a possible “compromise” solution to include in the legislation.

An independent energy policy expert, who was not involved with the study, described the analysis a “highly valuable contribution” after years in which segments of the automotive sector argued there was insufficient information to accurately assess actual emissions.

“The results show, without question, that the difference between official and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or conventional cars,” they said. “Any policy changes regarding PHEVs should be made with extreme care and in the light of this data.”