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Plug-in hybrid electric vehicles release nearly five times more global warming emissions than lab-reported data indicate, according to a new analysis.

Widening Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, based on analysis conducted by a non-profit group. This contrasts sharply with lab tests, which assumed a 75% decrease in pollution.

Researchers studied data from in-vehicle fuel consumption monitors of 800,000 vehicles sold in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” said a senior researcher involved in the study. “That discrepancy is growing and poses a significant problem. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Researchers attributed most of the gap to overestimates of the “utility factor” – the percentage of miles travelled in battery mode relative to total distance. The team found that just 27% of driving was completed in electric mode, whereas official estimates assumed 84%.

Even, when running in EV mode, pollution levels were significantly higher than lab estimates. This occurred because electric motors were not strong sufficient to function independently, leading to engines burning gasoline for nearly a third of the distance completed in EV mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV emissions allowed four major carmaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 extra per year in running expenses than would be estimated under lab tests.

“The strong statements that automakers like to make about their plug-in hybrid 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 cutting money. In reality, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into policy debates as automakers have lobbied the European Union to relax CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive industry and opposition from member states with large automotive manufacturing.

Several high-level politicians have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

One independent energy policy specialist, who was not involved with the research, described the report a “very useful contribution” after a long period in which parts of the automotive sector claimed there was insufficient information to accurately assess real-world emissions.

“These findings show, without question, that the gap between lab and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert said. “All policy adjustments concerning PHEVs should be made with extreme care and in the light of that evidence.”