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PHEVs release nearly 5x greater global warming emissions than lab-reported figures indicate, as per a new analysis.

Widening Gap Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel vehicles, based on research carried out by a advocacy organization. That differs significantly with lab tests, which assumed a 75% reduction in emissions.

Researchers studied data from onboard fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while official figures are falling,” stated a lead researcher participating in the report. “That discrepancy is growing and creates a significant problem. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in battery mode compared to overall mileage. The team determined that just a quarter of travel was completed in electric mode, whereas official estimates assumed over four-fifths.

Additionally, when running in EV mode, emission levels were well above official projections. That occurred because electric motors were insufficiently powerful enough to operate independently, resulting to engines using gasoline for almost one-third of the distance covered in electric mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV emissions enabled four large automaker groups to avoid over €5bn in penalties from 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 extra annually in running costs than is estimated under laboratory tests.

“The strong claims that automakers like to make about their PHEV cars are obviously far from the truth,” stated a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into political debates as carmakers have lobbied the EU to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with large automotive manufacturing.

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

One independent energy policy specialist, who was not involved with the research, called the analysis a “highly valuable contribution” after a long period in which parts of the car industry argued there was too little data to accurately assess real-world emissions.

“The results show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional cars,” they stated. “All policy changes concerning PHEVs should be made with extreme care and in the light of this data.”