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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating emissions than official figures indicate, as per a recent report.

Growing Gap Between Lab and Real-World CO2 Output

Statistics shows that PHEVs release just 19% less CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit group. This differs sharply with laboratory tests, which suggested a 75% decrease in pollution.

Researchers examined data from onboard fuel consumption monitors of 800,000 vehicles sold in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a lead analyst involved in the study. “This gap is growing and creates a significant issue. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Primary Factors Behind the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery mode relative to total mileage. They found that only 27% of travel was completed in electric mode, while official assumptions suggested 84%.

Additionally, when operating in electric mode, emission levels were significantly higher than official projections. This happened because electric motors were insufficiently powerful enough to function alone, leading to combustion motors using fossil fuels for almost a third of the distance completed in electric mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV emissions allowed four large automaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs would pay approximately €500 extra per year in operating expenses than is estimated under laboratory conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are obviously far from the mark,” commented a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are helping the environment and cutting money. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Hybrid vehicles have lately been brought again into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large car manufacturing.

Several senior politicians have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

One external energy policy specialist, who was unaffiliated with the study, described the report a “very useful contribution” after a long period in which parts of the car industry claimed there was too little data to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel cars,” the expert said. “All regulatory adjustments concerning PHEVs should be made with extreme care and in the light of this data.”