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Plug-in hybrid electric vehicles release nearly 5x more planet-heating pollution than lab-reported data show, according to a recent report.

Widening Discrepancy In Lab and Real-World CO2 Output

Data shows that PHEVs emit just 19% lower CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a advocacy organization. That contrasts significantly with laboratory tests, which assumed a 75% decrease in emissions.

Researchers examined data from onboard fuel consumption monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a senior analyst involved in the study. “This gap is growing and creates a significant issue. As a result, PHEVs pollute almost as much as gasoline cars.”

Key Factors Driving the Emissions Gap

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power relative to total mileage. The team determined that just 27% of travel was completed in electric mode, while official estimates assumed 84%.

Even, when running in EV mode, pollution amounts were significantly higher than lab projections. That happened because electric motors were not strong sufficient to operate alone, leading to engines burning gasoline for nearly a third of the distance covered in electric mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV CO2 output enabled several major automaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay about €500 extra annually in operating expenses than would be assumed under laboratory tests.

“The bold claims that automakers often promote about their PHEV cars are obviously way off the truth,” stated a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little better than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been brought back into political discussions as carmakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the car industry and resistance from EU countries with significant automotive industries.

Several senior officials have suggested plug-in hybrids as a possible “compromise” option to introduce in the regulation.

One independent energy policy specialist, who was not involved with the research, called the analysis a “highly valuable addition” after years in which parts of the car industry argued there was too little information to accurately assess real-world CO2 output.

“These findings demonstrate, without question, that the gap between lab and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” they stated. “All regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of this evidence.”