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PHEVs produce nearly 5x greater planet-heating pollution than official figures indicate, according to a recent report.

Growing Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs emit just 19% lower CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy organization. That contrasts sharply with laboratory tests, which assumed a 75% reduction in pollution.

Researchers examined data from in-vehicle energy use meters of 800,000 cars sold in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” stated a lead analyst involved in the study. “This discrepancy is growing and poses a significant issue. As a result, PHEVs emit nearly as heavily as petrol cars.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in battery mode compared to total distance. The team determined that just 27% of travel was done in EV mode, whereas lab assumptions assumed over four-fifths.

Even, when running in EV mode, emission amounts were significantly higher than official estimates. This occurred because EV motors were not strong sufficient to function independently, leading to combustion motors burning fossil fuels for nearly one-third of the travel covered in EV mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV emissions enabled several major carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 more annually in running costs than is assumed under lab tests.

“The bold claims that manufacturers like to make about their PHEV cars are clearly way off the mark,” commented a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little improved than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have lately been brought back into policy debates as carmakers have lobbied the EU to relax CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car sector and resistance from EU countries with large car manufacturing.

Some high-level officials have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

An external energy policy specialist, who was unaffiliated with the study, described the report a “very useful addition” after a long period in which parts of the automotive sector argued there was too little information to accurately evaluate actual CO2 output.

“The results show, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional cars,” they stated. “All regulatory adjustments regarding PHEVs should be made with extreme caution and in the light of this evidence.”