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Plug-in hybrid cars emit almost 5x more global warming emissions than official figures show, as per a new analysis.

Growing Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a advocacy organization. This differs significantly with lab tests, which suggested a 75% decrease in emissions.

Researchers studied information from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” stated a lead analyst involved in the report. “That gap is growing and creates a significant issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Key Reasons Behind the Discrepancy

Researchers linked most of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in battery mode compared to overall mileage. The team determined that just 27% of travel was done in electric mode, whereas official assumptions suggested 84%.

Additionally, when operating in electric mode, pollution levels were well above official projections. That occurred because EV motors were not strong enough to operate independently, leading to engines burning fossil fuels for almost one-third of the travel completed in electric mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV emissions allowed four large automaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend about €500 more per year in operating expenses than would be assumed under lab conditions.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and saving money. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have recently been drawn again into political discussions as automakers have lobbied the European Union to weaken CO₂ targets. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant automotive manufacturing.

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

One external energy policy expert, who was unaffiliated with the study, described the analysis a “highly valuable addition” after years in which segments of the automotive sector argued there was insufficient information to accurately evaluate real-world emissions.

“The results show, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel cars,” the expert said. “Any policy changes regarding PHEVs should be implemented with utmost care and in the light of that data.”