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Plug-in hybrid cars produce nearly 5x greater global warming pollution than lab-reported data show, as per a new analysis.

Widening Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth lower CO₂ than conventional petrol and diesel vehicles, according to research conducted by a advocacy group. This differs sharply with laboratory tests, which assumed a three-quarters decrease in emissions.

Researchers studied information from in-vehicle fuel consumption meters of 800,000 cars sold in the EU from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” said a lead analyst participating in the report. “This discrepancy is widening and poses a serious issue. As a result, PHEVs emit almost as heavily as petrol cars.”

Key Factors Behind the Discrepancy

Researchers attributed most of the gap to overestimates of the “electric driving share” – the ratio of miles driven in battery power relative to total distance. The team found that only a quarter of travel was done in EV mode, whereas lab assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution levels were well above lab projections. That happened because EV motors were not strong enough to function independently, leading to combustion motors burning fossil fuels for almost a third of the travel covered in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output allowed four large automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay approximately €500 extra annually in running costs than would be estimated under lab tests.

“The strong claims that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the truth,” commented a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and saving money. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Pressure

Hybrid vehicles have lately been brought back into policy debates as automakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced intense pressure from the car industry and opposition from EU countries with significant car industries.

Some high-level politicians have proposed plug-in hybrids as a possible “flexibility” option to introduce in the legislation.

An external energy economics specialist, who was not involved with the study, called the analysis a “very useful addition” after years in which parts of the car sector claimed there was too little information to accurately evaluate actual CO2 output.

“The results demonstrate, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel cars,” the expert said. “Any regulatory adjustments regarding PHEVs should be implemented with extreme caution and considering this data.”