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Plug-in hybrid cars produce almost 5x more global warming emissions than lab-reported data indicate, according to a new analysis.

Growing Discrepancy Between Official and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a advocacy group. This differs significantly with laboratory tests, which assumed a 75% reduction in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” said a lead analyst participating in the study. “That discrepancy is widening and poses a serious issue. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Key Factors Driving the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery mode compared to overall distance. They determined that only a quarter of travel was completed in EV mode, whereas lab estimates suggested over four-fifths.

Even, when running in electric mode, emission amounts were significantly higher than official projections. That happened because electric motors were not strong enough to operate independently, resulting to engines using gasoline for nearly a third of the travel completed in EV mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output allowed four large automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 extra annually in operating expenses than would be estimated under lab tests.

“The bold claims that automakers often promote about their PHEV vehicles are obviously far from the truth,” commented a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little better than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid cars have lately been drawn again into policy debates as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the car industry and resistance from EU countries with significant automotive industries.

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

An independent energy policy expert, who was unaffiliated with the research, called the report a “very useful addition” after years in which segments of the car industry claimed there was insufficient data to accurately assess real-world emissions.

“These findings show, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert stated. “Any policy adjustments regarding PHEVs should be made with extreme care and in the light of that data.”