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Plug-in hybrid cars emit almost 5x greater planet-heating emissions than official data indicate, according to a new analysis.

Widening Discrepancy In Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% lower CO₂ than traditional petrol and diesel vehicles, according to research carried out by a non-profit organization. This differs sharply with laboratory tests, which suggested a three-quarters decrease in emissions.

Researchers examined information from in-vehicle fuel consumption meters of eight hundred thousand cars sold in the EU between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a senior researcher involved in the study. “That gap is widening and poses a serious problem. Consequently, PHEVs pollute nearly as much as petrol cars.”

Primary Factors Driving the Discrepancy

Analysts linked most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in electric power relative to total mileage. The team found that only a quarter of travel was done in EV mode, while lab estimates suggested 84%.

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

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled four major automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 extra annually in operating expenses than would be estimated under laboratory conditions.

“The strong statements that manufacturers like to make about their PHEV vehicles are obviously far from the truth,” stated a transport analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Debate and Industry Pressure

Hybrid cars have recently been drawn again into political discussions as carmakers have pressed the European Union to relax CO₂ targets. 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 significant automotive manufacturing.

Some senior politicians have suggested plug-in hybrids as a potential “flexibility” solution to include in the legislation.

An independent energy policy specialist, who was unaffiliated with the study, called the analysis a “highly valuable addition” after a long period in which parts of the car sector claimed there was too little information to accurately evaluate real-world emissions.

“These findings show, beyond any doubt, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional cars,” they stated. “All regulatory changes concerning PHEVs should be made with utmost care and considering that data.”