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Plug-in hybrid cars release nearly 5x greater global warming emissions than lab-reported figures indicate, as per a new analysis.

Growing Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research carried out by a non-profit group. That differs sharply with laboratory tests, which suggested a three-quarters reduction in pollution.

Analysts studied information from in-vehicle fuel consumption meters of 800,000 vehicles registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” stated a lead analyst participating in the study. “That discrepancy is growing and poses a significant issue. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Key Reasons Behind the Discrepancy

Researchers linked most of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in electric power compared to total mileage. The team found that only a quarter of travel was completed in EV mode, while lab assumptions assumed 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab projections. That happened because EV motors were not strong sufficient to function alone, leading to engines burning fossil fuels for almost one-third of the distance covered in electric mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV CO2 output allowed several large carmaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could spend about €500 more annually in operating costs than would be assumed under laboratory conditions.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Lobbying

Hybrid cars have lately been drawn again into policy debates as carmakers have pressed the European Union to relax CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with significant automotive manufacturing.

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

An external energy economics specialist, who was not involved with the research, called the report a “highly valuable contribution” after years in which segments of the car sector argued there was too little information to properly evaluate actual emissions.

“These findings demonstrate, without question, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or conventional cars,” the expert stated. “All policy adjustments concerning PHEVs should be made with extreme caution and considering that evidence.”