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PHEVs produce almost 5x more planet-heating pollution than lab-reported data indicate, according to a new analysis.

Growing Gap Between Lab and Real-World Emissions

Data reveals that PHEVs emit just 19% less CO₂ than traditional petrol and diesel cars, based on analysis conducted by a advocacy group. That differs sharply with lab tests, which suggested a 75% reduction in pollution.

Analysts studied information from in-vehicle energy use meters of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” said a lead analyst participating in the study. “That gap is growing and creates a significant problem. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to total mileage. They found that only a quarter of travel was completed in electric mode, whereas official assumptions assumed over four-fifths.

Additionally, when operating in EV mode, pollution levels were well above official estimates. That occurred because electric motors were not strong enough to operate independently, leading to combustion motors using gasoline for almost a third of the travel covered in electric mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed four major automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 more per year in running costs than would be assumed under lab tests.

“The bold claims that automakers like to make about their PHEV cars are obviously far from the truth,” stated a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid cars have lately been brought again into policy discussions as carmakers have lobbied the European Union to relax CO₂ targets. A proposed ban on new combustion engine cars in 2035 has faced intense pressure from the car sector and opposition from member states with large automotive industries.

Some senior officials have proposed PHEVs as a potential “flexibility” option to include in the legislation.

One independent energy policy specialist, who was not involved with the study, called the analysis a “very useful contribution” after a long period in which parts of the automotive sector claimed there was insufficient information to accurately assess real-world emissions.

“The results demonstrate, without question, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or conventional cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and considering this evidence.”