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PHEVs emit almost 5x more planet-heating pollution than lab-reported figures indicate, according to a new report.

Widening Gap In Official and Real-World CO2 Output

Statistics shows that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to research conducted by a advocacy group. This differs significantly with laboratory estimates, which suggested a three-quarters decrease in emissions.

Analysts studied data from onboard fuel consumption monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” said a senior researcher involved in the study. “That discrepancy is widening and creates a significant problem. As a result, PHEVs pollute almost as much as petrol cars.”

Key Factors Behind the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in electric mode relative to total mileage. They determined that just a quarter of driving was done in EV mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, emission amounts were significantly higher than official projections. This occurred because electric motors were insufficiently powerful enough to operate alone, leading to engines burning gasoline for nearly a third of the travel covered in EV mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output allowed several large automaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 extra annually in running expenses than would be assumed under lab tests.

“The bold claims that automakers often promote about their plug-in hybrid cars are obviously far from the mark,” commented a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have lately been drawn again into policy discussions as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from member states with large car industries.

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

An external energy policy expert, who was not involved with the study, described the report a “highly valuable contribution” after a long period in which parts of the automotive sector claimed there was insufficient information to properly assess real-world CO2 output.

“The results show, without question, that the difference between official and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel cars,” they stated. “All policy adjustments concerning PHEVs should be implemented with utmost caution and in the light of that data.”