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

Growing Gap In Official and Real-World CO2 Output

Statistics reveals that PHEVs release just one-fifth less CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a advocacy organization. This differs significantly with lab estimates, which assumed a three-quarters decrease in pollution.

Analysts studied information from in-vehicle energy use monitors of 800,000 vehicles registered in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” stated a senior researcher involved in the study. “That gap is growing and poses a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to overall mileage. The team determined that just 27% of driving was done in electric mode, while lab assumptions suggested 84%.

Even, when running in electric mode, pollution levels were well above official projections. That occurred because EV motors were not strong sufficient to function alone, resulting to combustion motors burning fossil fuels for nearly one-third of the travel completed in electric mode.

Regulatory and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output enabled four major carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 extra per year in operating costs than would be assumed under laboratory conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” stated a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn back into policy debates as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large car industries.

Several high-level politicians have suggested plug-in hybrids as a possible “flexibility” option to introduce in the legislation.

An independent energy economics expert, who was not involved with the research, described the report a “highly valuable addition” after a long period in which parts of the automotive sector argued there was too little information to properly evaluate actual CO2 output.

“The results demonstrate, without question, that the gap between official and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or conventional cars,” they said. “All regulatory changes concerning PHEVs should be implemented with utmost caution and considering that data.”