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Plug-in hybrid cars produce nearly 5x greater planet-heating pollution than lab-reported figures show, according to a new analysis.

Widening Discrepancy In Lab and Actual Emissions

Data reveals that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel vehicles, according to research conducted by a advocacy organization. That differs significantly with laboratory tests, which suggested a three-quarters reduction in pollution.

Analysts examined data from in-vehicle fuel consumption meters of eight hundred thousand cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” stated a lead researcher participating in the report. “That gap is widening and creates a significant problem. As a result, PHEVs emit nearly as much as petrol cars.”

Primary Reasons Driving the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles driven in battery mode compared to total distance. The team determined that only a quarter of driving was done in electric mode, while lab estimates suggested 84%.

Even, when operating in electric mode, pollution levels were well above lab projections. That happened because electric motors were insufficiently powerful enough to operate alone, resulting to combustion motors burning gasoline for nearly a third of the distance covered in EV mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output allowed four large carmaker companies to escape more than €5bn in penalties from 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 more per year in operating expenses than would be assumed under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are clearly far from the truth,” commented a transport expert. “Consumers are being duped into thinking that by buying 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 energy consumption, CO₂ production, and operating costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have lately been brought back into political discussions as carmakers have pressed the European Union to weaken CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large car industries.

Several senior officials have suggested PHEVs as a potential “flexibility” solution to include in the legislation.

One independent energy economics expert, who was not involved with the research, called the analysis a “very useful contribution” after years in which parts of the automotive industry claimed there was too little information to properly evaluate real-world CO2 output.

“These findings show, without question, that the gap in official and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel cars,” the expert said. “All regulatory adjustments concerning PHEVs should be made with extreme care and in the light of that data.”