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Plug-in hybrid electric vehicles release almost five times more global warming emissions than official figures show, according to a new report.

Widening Gap In Lab and Actual Emissions

Statistics shows that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel cars, based on analysis carried out by a non-profit organization. That differs sharply with laboratory estimates, which suggested a 75% reduction in pollution.

Analysts studied data from in-vehicle fuel consumption monitors of 800,000 cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Real-world emissions are rising, while official figures are falling,” stated a senior researcher participating in the study. “This gap is widening and creates a serious problem. As a result, PHEVs pollute nearly as much as petrol cars.”

Primary Reasons Behind the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in electric power relative to overall mileage. The team found that just a quarter of driving was done in electric mode, while official assumptions assumed 84%.

Even, when operating in EV mode, pollution levels were well above lab projections. This happened because electric motors were not strong sufficient to function independently, resulting to engines burning gasoline for almost one-third of the travel completed in electric mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV emissions enabled several large automaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend about €500 more per year in running costs than is estimated under lab conditions.

“The bold statements that automakers like to make about their PHEV vehicles are clearly far from the mark,” commented a automotive analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Political Discussion and Industry Pressure

Hybrid vehicles have recently been drawn again into policy debates as automakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and opposition from EU countries with large car manufacturing.

Several high-level officials have suggested plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

One independent energy economics expert, who was unaffiliated with the study, described the report a “very useful addition” after years in which segments of the car industry argued there was too little data to properly evaluate actual emissions.

“These findings show, beyond any doubt, that the gap in official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” the expert said. “All policy adjustments concerning PHEVs should be implemented with extreme caution and considering that evidence.”