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Plug-in hybrid cars emit almost 5x greater planet-heating emissions than lab-reported figures indicate, according to a recent report.

Widening Gap Between Lab and Actual CO2 Output

Data shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel vehicles, based on research carried out by a non-profit group. That differs sharply with lab tests, which suggested a three-quarters reduction in pollution.

Analysts studied information from in-vehicle energy use meters of 800,000 vehicles registered in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” stated a lead researcher participating in the study. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Key Reasons Driving the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric mode compared to overall distance. They determined that just 27% of driving was completed in EV mode, while official estimates assumed over four-fifths.

Additionally, when running in EV mode, emission amounts were well above official estimates. This occurred because EV motors were insufficiently powerful enough to function independently, leading to combustion motors burning fossil fuels for almost a third of the travel completed in electric mode.

Policy and Financial Consequences

According to calculations, the lowballing of PHEV emissions allowed four major automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 extra per year in running expenses than is assumed under laboratory tests.

“The bold claims that automakers often promote about their PHEV vehicles are clearly far from the truth,” stated a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Discussion and Industry Pressure

Hybrid cars have recently been drawn again into political debates as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and resistance from member states with significant car manufacturing.

Several high-level officials have suggested PHEVs as a possible “flexibility” solution to introduce in the regulation.

One independent energy policy expert, who was unaffiliated with the study, called the analysis a “highly valuable addition” after a long period in which parts of the car industry claimed there was too little data to accurately assess real-world CO2 output.

“The results demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional vehicles,” the expert said. “Any regulatory changes concerning PHEVs should be made with utmost caution and considering this evidence.”