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Plug-in hybrid cars produce nearly 5x more global warming pollution than official data show, as per a new analysis.

Widening Gap In Official and Real-World Emissions

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy organization. This contrasts significantly with laboratory estimates, which assumed a three-quarters reduction in pollution.

Analysts examined data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” said a lead researcher involved in the study. “That discrepancy is growing and creates a serious issue. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Reasons Behind the Discrepancy

Researchers linked most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in electric mode relative to total distance. They found that just 27% of travel was done in EV mode, whereas official assumptions assumed 84%.

Even, when running in EV mode, emission amounts were well above official estimates. This occurred because electric motors were not strong enough to function alone, resulting to combustion motors burning gasoline for nearly a third of the distance completed in electric mode.

Regulatory and Financial Consequences

According to estimates, the underestimation of PHEV emissions enabled four large carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could pay about €500 more annually in running expenses than would be estimated under laboratory tests.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running expenses.”

Political Discussion and Industry Pressure

Hybrid vehicles have lately been brought back into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and resistance from EU countries with large automotive manufacturing.

Some high-level politicians have proposed plug-in hybrids as a possible “compromise” option to introduce in the regulation.

An independent energy policy expert, who was unaffiliated with the study, called the analysis a “highly valuable contribution” after years in which segments of the car sector claimed there was insufficient information to accurately evaluate actual CO2 output.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or diesel cars,” the expert said. “All policy changes concerning PHEVs should be implemented with utmost care and considering that evidence.”