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Plug-in hybrid cars release nearly 5x more global warming emissions than lab-reported figures show, according to a recent analysis.

Growing Gap Between Official and Actual Emissions

Data reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel cars, according to research carried out by a advocacy group. That contrasts significantly with laboratory tests, which assumed a 75% reduction in emissions.

Researchers studied data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” said a senior researcher involved in the study. “This gap is growing and creates a significant issue. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Primary Factors Behind the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric power compared to overall distance. They determined that only 27% of driving was completed in EV mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, pollution levels were well above lab estimates. This occurred because electric motors were insufficiently powerful sufficient to function alone, leading to engines using gasoline for almost a third of the distance covered in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled four large automaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 extra annually in operating costs than is assumed under lab conditions.

“The bold claims that manufacturers often promote about their PHEV cars are clearly far from the mark,” commented a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Political Discussion and Automotive Pressure

Hybrid vehicles have recently been brought again into policy debates as automakers have pressed the European Union to relax CO₂ targets. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced intense pressure from the car industry and resistance from EU countries with large car manufacturing.

Some high-level politicians have suggested PHEVs as a potential “flexibility” solution to include in the regulation.

An independent energy economics specialist, who was not involved with the research, described the analysis a “highly valuable addition” after years in which segments of the car industry argued there was insufficient information to properly assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” they stated. “All policy adjustments regarding PHEVs should be implemented with utmost caution and considering this evidence.”