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Plug-in hybrid cars release nearly five times more planet-heating pollution than official figures show, according to a new report.

Growing Discrepancy In Official and Actual CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel cars, based on research carried out by a advocacy group. That differs sharply with laboratory estimates, which assumed a 75% reduction in emissions.

Researchers examined information from in-vehicle energy use meters of 800,000 cars sold in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” stated a lead analyst involved in the study. “That gap is growing and creates a serious issue. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to total distance. The team determined that just a quarter of driving was done in EV mode, while lab estimates assumed over four-fifths.

Additionally, when operating in electric mode, emission amounts were significantly higher than official projections. This occurred because electric motors were not strong sufficient to operate alone, leading to engines burning gasoline for almost a third of the distance completed in electric mode.

Policy and Financial Consequences

According to calculations, the lowballing of PHEV CO2 output allowed four large carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 more per year in running expenses than would be assumed under laboratory tests.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the truth,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Hybrid cars have lately been brought again into political discussions as carmakers have pressed the European Union to relax CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive sector and opposition from member states with large car manufacturing.

Several senior politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

One external energy economics expert, who was not involved with the research, called the report a “highly valuable contribution” after a long period in which parts of the car industry argued there was too little data to accurately evaluate real-world emissions.

“These findings show, beyond any doubt, that the gap between lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional cars,” the expert stated. “All regulatory adjustments regarding PHEVs should be made with extreme caution and considering this evidence.”