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Plug-in hybrid electric vehicles release almost five times more planet-heating pollution than lab-reported data show, according to a recent report.

Growing Discrepancy In Lab and Real-World Emissions

Statistics reveals that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel cars, based on research conducted by a non-profit group. This differs sharply with laboratory tests, which assumed a three-quarters decrease in emissions.

Researchers examined information from onboard energy use monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” stated a lead analyst participating in the report. “That discrepancy is growing and poses a significant issue. Consequently, PHEVs emit almost as much as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “utility factor” – the percentage of miles travelled in electric power relative to total mileage. The team determined that just a quarter of travel was completed in electric mode, whereas official estimates suggested 84%.

Even, when operating in electric mode, pollution levels were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful sufficient to function independently, leading to engines burning gasoline for almost one-third of the travel covered in electric mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output allowed several major automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could spend about €500 more annually in running expenses than is assumed under lab tests.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the truth,” stated a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been brought back into political debates as carmakers have lobbied the EU to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and resistance from EU countries with large automotive industries.

Several senior politicians have proposed PHEVs as a potential “compromise” option to include in the legislation.

One independent energy economics expert, who was unaffiliated with the research, called the report a “very useful contribution” after years in which segments of the car sector argued there was too little information to properly assess actual CO2 output.

“These findings demonstrate, without question, that the gap in official and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” the expert stated. “All policy adjustments regarding PHEVs should be made with utmost caution and in the light of that evidence.”