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Plug-in hybrid cars emit almost 5x greater global warming emissions than official data indicate, according to a recent report.

Widening Discrepancy In Official and Real-World Emissions

Statistics reveals that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel cars, based on research conducted by a non-profit organization. That contrasts sharply with laboratory tests, which assumed a three-quarters decrease in pollution.

Researchers studied information from in-vehicle fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” said a senior analyst involved in the study. “This gap is widening and creates a significant issue. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in battery power compared to overall distance. They determined that just 27% of travel was completed in EV mode, whereas official assumptions assumed over four-fifths.

Additionally, when running in EV mode, pollution levels were significantly higher than official projections. This occurred because EV motors were not strong sufficient to operate alone, resulting to combustion motors burning fossil fuels for nearly a third of the distance covered in electric mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV emissions allowed several major carmaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 more per year in operating expenses than is estimated under laboratory conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the mark,” commented a automotive expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little improved than regular gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have lately been brought again into policy discussions as automakers have pressed the EU to relax CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy pressure from the car industry and resistance from member states with large automotive industries.

Several senior politicians have suggested PHEVs as a potential “flexibility” option to introduce in the legislation.

One independent energy policy expert, who was not involved with the research, called the report a “highly valuable addition” after a long period in which segments of the automotive sector argued there was too little data to accurately assess real-world emissions.

“The results show, beyond any doubt, that the difference in lab and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel vehicles,” the expert said. “All regulatory changes regarding PHEVs should be made with extreme care and considering that data.”