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Plug-in hybrid cars produce nearly five times greater global warming emissions than official figures indicate, as per a new analysis.

Growing Gap Between Official and Actual Emissions

Data reveals that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel vehicles, according to research carried out by a advocacy organization. That contrasts sharply with laboratory tests, which assumed a 75% reduction in pollution.

Researchers studied data from in-vehicle fuel consumption meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a lead analyst participating in the report. “That discrepancy is widening and creates a serious issue. As a result, PHEVs emit almost as heavily as gasoline cars.”

Key Reasons Behind the Discrepancy

Researchers linked most of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric mode relative to total mileage. They found that just 27% of driving was completed in EV mode, whereas official assumptions suggested 84%.

Additionally, when running in electric mode, pollution levels were well above lab projections. That occurred because electric motors were not strong enough to operate alone, leading to engines burning fossil fuels for nearly a third of the travel covered in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several major automaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs would pay about €500 more annually in operating costs than would be assumed under lab conditions.

“The bold claims that automakers like to make about their PHEV vehicles are obviously way off the truth,” stated a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little improved than regular gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Debate and Industry Pressure

Hybrid cars have recently been brought again into political debates as automakers have pressed the EU to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with large automotive industries.

Several senior politicians have suggested PHEVs as a possible “flexibility” option to include in the regulation.

One external energy policy expert, who was not involved with the research, described the analysis a “highly valuable addition” after years in which segments of the car sector argued there was too little data to accurately evaluate real-world CO2 output.

“These findings demonstrate, without question, that the difference in lab and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” they stated. “All regulatory adjustments concerning PHEVs should be made with utmost care and considering this evidence.”