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

Growing Gap In Lab and Real-World CO2 Output

Statistics shows that PHEVs release only 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit organization. This differs sharply with lab tests, which suggested a 75% decrease in pollution.

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

“Actual CO2 output are rising, while official figures are decreasing,” said a lead researcher participating in the study. “This discrepancy is growing and creates a significant problem. As a result, PHEVs emit nearly as much as petrol cars.”

Primary Factors Behind the Discrepancy

Researchers linked most of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in electric mode compared to overall mileage. They determined that only 27% of travel was done in EV mode, whereas lab estimates assumed over four-fifths.

Additionally, when running in electric mode, pollution amounts were significantly higher than lab estimates. That occurred because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors using gasoline for almost one-third of the distance completed in electric mode.

Policy and Economic Implications

Based on calculations, the underestimation of PHEV emissions enabled four major carmaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 more per year in running costs than would be estimated under laboratory conditions.

“The strong claims that automakers like to make about their PHEV cars are obviously far from the mark,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Political Debate and Automotive Lobbying

Hybrid vehicles have recently been drawn again into policy discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with large car industries.

Some high-level officials have suggested plug-in hybrids as a potential “compromise” option to introduce in the legislation.

An external energy economics expert, who was not involved with the study, called the analysis a “highly valuable addition” after years in which parts of the car sector argued there was insufficient information to properly assess real-world emissions.

“The results show, beyond any doubt, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or diesel cars,” the expert stated. “Any policy changes regarding PHEVs should be implemented with extreme care and considering that evidence.”