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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating pollution than lab-reported data indicate, as per a recent report.

Widening Gap In Official and Real-World CO2 Output

Statistics shows that PHEVs emit only 19% less CO₂ than conventional petrol and diesel cars, based on analysis carried out by a advocacy group. That differs significantly with laboratory tests, which assumed a three-quarters decrease in pollution.

Analysts examined data from in-vehicle energy use meters of 800,000 cars registered in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” said a lead analyst involved in the study. “This discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Behind the Discrepancy

Researchers attributed most of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode compared to total distance. The team determined that only a quarter of driving was completed in EV mode, while official assumptions suggested 84%.

Additionally, when running in electric mode, pollution amounts were significantly higher than lab estimates. That happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to engines using fossil fuels for nearly a third of the distance covered in electric mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four major carmaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 extra per year in running costs than would be estimated under lab tests.

“The bold statements that automakers often promote about their PHEV vehicles are clearly way off the mark,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of fuel consumption, CO₂ production, and running expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have recently been brought again into policy discussions as carmakers have lobbied the European Union to relax CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with large car manufacturing.

Some senior officials have suggested PHEVs as a possible “compromise” solution to include in the legislation.

One external energy economics specialist, who was unaffiliated with the research, described the report a “highly valuable contribution” after a long period in which segments of the car sector claimed there was insufficient data to properly assess real-world CO2 output.

“The results demonstrate, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel vehicles,” the expert said. “All regulatory adjustments regarding PHEVs should be implemented with utmost care and considering this evidence.”