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Plug-in hybrid cars produce almost 5x greater planet-heating pollution than official data show, as per a new analysis.

Widening Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs emit just 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a advocacy organization. That differs significantly with laboratory tests, which suggested a 75% reduction in emissions.

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

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” stated a senior analyst involved in the report. “That discrepancy is widening and creates a serious issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Key Factors Behind the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power compared to overall mileage. The team determined that only 27% of travel was completed in EV mode, while official assumptions suggested 84%.

Additionally, when operating in electric mode, pollution amounts were significantly higher than lab projections. That happened because electric motors were not strong enough to function alone, resulting to combustion motors burning fossil fuels for almost one-third of the travel covered in EV mode.

Regulatory and Economic Implications

According to calculations, the lowballing of PHEV emissions allowed several major carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 extra per year in running costs than would be estimated under laboratory tests.

“The bold claims that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel use, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been brought again into policy discussions as carmakers have lobbied the EU to weaken CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with significant car manufacturing.

Several high-level officials have suggested PHEVs as a possible “flexibility” solution to include in the regulation.

One external energy policy expert, who was unaffiliated with the study, called the analysis a “highly valuable addition” after a long period in which parts of the car sector argued there was insufficient information to accurately assess real-world emissions.

“The results show, without question, that the difference in official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel cars,” the expert said. “All regulatory changes concerning PHEVs should be implemented with extreme care and in the light of this data.”