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Plug-in hybrid electric vehicles release almost 5x more global warming pollution than lab-reported data indicate, as per a new analysis.

Widening Gap Between Lab and Actual Emissions

Statistics shows that PHEVs emit just 19% less CO₂ than conventional gas and diesel cars, according to analysis carried out by a non-profit organization. This contrasts significantly with laboratory tests, which suggested a 75% reduction in pollution.

Researchers examined information from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” stated a senior analyst participating in the study. “This discrepancy is growing and creates a serious problem. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Factors Behind the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in electric power relative to overall mileage. They determined that only a quarter of travel was completed in EV mode, whereas official assumptions suggested over four-fifths.

Even, when running in electric mode, pollution amounts were significantly higher than lab projections. That happened because electric motors were not strong sufficient to operate alone, resulting to engines burning gasoline for almost a third of the travel completed in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output enabled four major automaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 more per year in operating costs than would be assumed under laboratory tests.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are obviously far from the mark,” commented a automotive expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have recently been brought back into policy discussions as automakers have lobbied the EU to relax CO₂ standards. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with large automotive manufacturing.

Some senior officials have proposed plug-in hybrids as a potential “flexibility” option to include in the regulation.

An external energy economics specialist, who was unaffiliated with the research, called the report a “highly valuable contribution” after years in which parts of the automotive sector argued there was too little data to accurately evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” they said. “Any policy adjustments regarding PHEVs should be made with extreme caution and in the light of this evidence.”