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Plug-in hybrid cars produce almost five times more global warming pollution than official data show, according to a new report.

Growing Gap Between Lab and Actual CO2 Output

Statistics reveals that PHEVs release only 19% lower CO₂ than conventional gas and diesel cars, according to research carried out by a non-profit group. This contrasts sharply with laboratory estimates, which assumed a three-quarters reduction in pollution.

Researchers examined information from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” said a lead analyst participating in the study. “This gap is widening and poses a significant issue. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Researchers linked most of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to overall mileage. The team found that just a quarter of driving was done in EV mode, while official assumptions suggested 84%.

Additionally, when operating in electric mode, pollution amounts were well above lab projections. That happened because EV motors were insufficiently powerful sufficient to operate independently, resulting to combustion motors using fossil fuels for almost a third of the distance completed in electric mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV CO2 output allowed several major automaker companies to avoid over €5bn in penalties from 2021 and 2023, by falsely easing adherence with EU average fleet CO₂ targets.

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

“The strong claims that manufacturers like to make about their PHEV vehicles are clearly way off the truth,” stated a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the environment and saving costs. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been brought again into political discussions as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the car industry and resistance from EU countries with large car manufacturing.

Several high-level officials have proposed PHEVs as a potential “flexibility” solution to introduce in the regulation.

One external energy policy specialist, who was not involved with the research, described the report a “highly valuable addition” after years in which segments of the automotive industry argued there was insufficient data to accurately evaluate real-world CO2 output.

“These findings show, without question, that the gap between official and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel cars,” the expert said. “Any regulatory adjustments regarding PHEVs should be implemented with utmost caution and in the light of this evidence.”