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Plug-in hybrid cars produce almost five times more planet-heating pollution than official figures indicate, according to a new report.

Growing Discrepancy Between Official and Real-World Emissions

Statistics shows that PHEVs emit only 19% less CO₂ than traditional gas and diesel vehicles, according to research carried out by a advocacy group. That contrasts significantly with laboratory estimates, which assumed a 75% decrease in pollution.

Researchers studied information from onboard energy use meters of eight hundred thousand vehicles sold in Europe from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” stated a lead analyst participating in the study. “That discrepancy is growing and creates a significant problem. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Driving the Discrepancy

Analysts attributed most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery power relative to total mileage. The team determined that only 27% of driving was completed in electric mode, while lab assumptions assumed over four-fifths.

Additionally, when running in electric mode, pollution levels were significantly higher than official projections. That occurred because EV motors were not strong enough to operate alone, leading to combustion motors burning gasoline for nearly one-third of the travel completed in electric mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed several major automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 extra annually in running costs than is estimated under laboratory tests.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are clearly way off the truth,” commented a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little better than standard gas and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Political Discussion and Automotive Lobbying

Hybrid cars have lately been drawn again into policy discussions as carmakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with large automotive manufacturing.

Several high-level officials have proposed plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

One independent energy economics specialist, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after years in which parts of the car industry argued there was too little data to accurately assess actual CO2 output.

“These findings demonstrate, without question, that the difference in lab and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel cars,” the expert said. “All regulatory adjustments regarding PHEVs should be made with utmost caution and considering this data.”