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PHEVs produce nearly five times more planet-heating emissions than lab-reported figures show, as per a new report.

Growing Gap Between Official and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth lower CO₂ than conventional petrol and diesel cars, according to research carried out by a advocacy group. That contrasts sharply with lab tests, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are falling,” said a senior researcher participating in the study. “That gap is growing and creates a significant problem. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Researchers linked most of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to overall mileage. The team found that just a quarter of travel was completed in EV mode, whereas lab assumptions suggested 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than official projections. This happened because EV motors were insufficiently powerful sufficient to operate independently, resulting to engines using gasoline for nearly one-third of the travel completed in EV mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output allowed several major carmaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 more annually in running costs than is estimated under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are obviously far from the mark,” commented a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and running expenses.”

Political Debate and Industry Pressure

Hybrid vehicles have recently been drawn again into political discussions as automakers have pressed the European Union to weaken CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and resistance from member states with large automotive manufacturing.

Several high-level politicians have proposed PHEVs as a potential “flexibility” option to include in the regulation.

One independent energy economics expert, who was not involved with the study, described the report a “highly valuable addition” after years in which parts of the automotive sector argued there was insufficient data to properly evaluate real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference in official and actual PHEV energy use and CO₂ output is significantly greater than for petrol or conventional cars,” they stated. “Any regulatory changes regarding PHEVs should be made with extreme caution and in the light of this evidence.”