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PHEVs emit almost five times more global warming pollution than lab-reported data show, according to a recent report.

Widening Gap In Official and Actual CO2 Output

Data shows that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis carried out by a advocacy group. That contrasts sharply with laboratory tests, which suggested a three-quarters reduction in pollution.

Analysts examined data from onboard fuel consumption meters of 800,000 cars registered in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” stated a senior researcher participating in the report. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Analysts attributed most of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in battery mode compared to overall distance. They determined that only 27% of travel was completed in EV mode, while official estimates assumed 84%.

Additionally, when running in electric mode, pollution levels were well above official estimates. That happened because EV motors were insufficiently powerful enough to function alone, leading to engines using gasoline for nearly a third of the travel covered in electric mode.

Regulatory and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output enabled several large carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay about €500 extra annually in running costs than would be assumed under lab tests.

“The strong claims that automakers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a transport expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have recently been drawn back into policy debates as automakers have pressed the EU to weaken CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from member states with significant car manufacturing.

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

One external energy economics specialist, who was unaffiliated with the study, called the report a “very useful contribution” after years in which parts of the car sector argued there was insufficient data to properly evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or diesel cars,” the expert stated. “Any regulatory changes concerning PHEVs should be made with extreme care and considering this evidence.”