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

Widening Discrepancy Between Official and Real-World Emissions

Statistics reveals that PHEVs emit just 19% lower CO₂ than conventional gas and diesel vehicles, based on research conducted by a advocacy organization. That contrasts sharply with lab tests, which assumed a three-quarters decrease in pollution.

Researchers examined information from in-vehicle energy use meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” said a senior researcher participating in the study. “This discrepancy is widening and creates a significant problem. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power relative to total mileage. The team determined that only 27% of travel was completed in EV mode, while lab estimates assumed over four-fifths.

Additionally, when operating in EV mode, pollution levels were well above lab projections. This occurred because EV motors were insufficiently powerful enough to operate alone, resulting to combustion motors burning gasoline for nearly a third of the travel covered in EV mode.

Regulatory and Economic Implications

According to calculations, the lowballing of PHEV emissions allowed four large automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 more per year in running expenses than is assumed under laboratory tests.

“The bold claims that automakers often promote about their PHEV vehicles are clearly way off the truth,” stated a transport analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have lately been brought back into policy debates as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant car industries.

Some senior officials have proposed plug-in hybrids as a potential “compromise” solution to include in the legislation.

One independent energy policy expert, who was not involved with the study, called the analysis a “very useful addition” after years in which segments of the automotive sector argued there was insufficient information to accurately evaluate actual emissions.

“These findings show, beyond any doubt, that the gap in lab and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” they said. “Any policy changes concerning PHEVs should be implemented with utmost caution and considering this data.”