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Plug-in hybrid electric vehicles produce nearly 5x more planet-heating emissions than official data show, according to a new analysis.

Widening Discrepancy Between Official and Actual CO2 Output

Statistics shows that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, according to research carried out by a non-profit organization. This differs sharply with laboratory estimates, which assumed a three-quarters decrease in emissions.

Researchers examined information from onboard energy use monitors of 800,000 vehicles sold in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” stated a senior researcher participating in the study. “This discrepancy is growing and creates a significant issue. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Factors Behind the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the ratio of miles travelled in battery mode compared to total distance. The team found that only a quarter of travel was done in EV mode, while lab assumptions suggested over four-fifths.

Additionally, when running in EV mode, pollution levels were well above official estimates. That occurred because EV motors were not strong enough to function independently, leading to combustion motors using gasoline for almost one-third of the distance completed in EV mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output enabled several major carmaker groups to escape over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 more per year in operating expenses than would be estimated under lab tests.

“The bold claims that automakers like to make about their PHEV cars are obviously way off the mark,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Debate and Automotive Lobbying

Hybrid vehicles have recently been brought again into political discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with large automotive manufacturing.

Several senior officials have suggested plug-in hybrids as a possible “flexibility” option to introduce in the legislation.

An external energy policy expert, who was not involved with the research, described the analysis a “highly valuable contribution” after years in which segments of the car sector argued there was too little information to properly assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel cars,” the expert stated. “Any policy changes regarding PHEVs should be made with extreme care and in the light of that evidence.”