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Plug-in hybrid electric vehicles emit almost five times more global warming emissions than lab-reported data show, as per a new analysis.

Growing Gap Between Lab and Real-World CO2 Output

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a advocacy organization. That differs significantly with lab estimates, which assumed a 75% decrease in emissions.

Analysts examined data from onboard fuel consumption monitors of eight hundred thousand cars sold in Europe from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a senior researcher involved in the report. “This discrepancy is growing and poses a significant problem. As a result, PHEVs emit almost as much as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in electric power compared to total mileage. They found that just a quarter of travel was completed in EV mode, while lab assumptions assumed over four-fifths.

Even, when running in electric mode, emission amounts were significantly higher than lab projections. This happened because electric motors were not strong enough to function independently, resulting to combustion motors burning fossil fuels for almost one-third of the travel completed in EV mode.

Regulatory and Financial Consequences

According to calculations, the lowballing of PHEV CO2 output allowed four large automaker companies to escape more than €5bn in penalties from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in operating expenses than is assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their plug-in hybrid cars are clearly far from the truth,” stated a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Lobbying

Hybrid cars have recently been drawn back into political discussions as carmakers have lobbied the European Union to relax CO₂ standards. A proposed ban on new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and resistance from member states with large car industries.

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

One independent energy economics expert, who was not involved with the research, called the report a “very useful addition” after years in which segments of the automotive sector argued there was insufficient information to properly assess real-world CO2 output.

“The results show, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel cars,” they stated. “Any regulatory changes regarding PHEVs should be made with extreme caution and in the light of this data.”