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Plug-in hybrid cars emit nearly five times greater planet-heating pollution than official data show, according to a new analysis.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics shows that PHEVs release only 19% lower CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a advocacy organization. This contrasts significantly with laboratory estimates, which assumed a three-quarters decrease in pollution.

Researchers examined information from onboard energy use monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” said a senior researcher involved in the report. “That gap is widening and poses a significant problem. As a result, PHEVs emit almost as much as gasoline vehicles.”

Key Reasons Behind the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode compared to overall distance. They determined that just 27% of driving was done in EV mode, while official estimates suggested over four-fifths.

Additionally, when running in electric mode, emission amounts were significantly higher than official estimates. That happened because EV motors were not strong sufficient to operate alone, resulting to combustion motors burning fossil fuels for almost one-third of the travel completed in electric mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV emissions allowed four major automaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs would spend approximately €500 more per year in operating expenses than would be estimated under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn again into political discussions as automakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with significant automotive manufacturing.

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

An independent energy economics specialist, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the car sector claimed there was too little data to properly evaluate actual emissions.

“These findings show, without question, that the gap between lab and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional cars,” they stated. “Any regulatory changes regarding PHEVs should be made with utmost caution and in the light of that evidence.”