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Plug-in hybrid cars produce almost 5x greater global warming pollution than lab-reported data show, according to a new report.

Widening Discrepancy In Lab and Real-World CO2 Output

Data reveals that PHEVs release only 19% lower CO₂ than traditional petrol and diesel vehicles, according to research carried out by a advocacy group. This contrasts significantly with lab tests, which suggested a 75% reduction in emissions.

Analysts studied information from in-vehicle energy use monitors of eight hundred thousand cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a lead analyst participating in the report. “That gap is widening and poses a significant issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the percentage of miles driven in battery power relative to overall mileage. They determined that only a quarter of driving was done in electric mode, while lab assumptions assumed 84%.

Additionally, when running in EV mode, pollution amounts were well above lab projections. That occurred because EV motors were insufficiently powerful sufficient to function alone, resulting to combustion motors using gasoline for almost one-third of the travel completed in electric mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled several major automaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend about €500 extra per year in operating expenses than would be assumed under laboratory tests.

“The strong statements that automakers like to make about their PHEV vehicles are obviously far from the truth,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have lately been brought again into political discussions as automakers have pressed the European Union to relax CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced intense pressure from the car sector and opposition from member states with significant car industries.

Several senior politicians have suggested PHEVs as a potential “flexibility” solution to introduce in the regulation.

One independent energy economics expert, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which parts of the automotive industry claimed there was insufficient data to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or diesel cars,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and in the light of that evidence.”