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Plug-in hybrid cars emit nearly 5x greater global warming emissions than lab-reported data show, according to a new analysis.

Widening Discrepancy In Official and Actual CO2 Output

Statistics shows that PHEVs release just 19% lower CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy group. This differs sharply with laboratory estimates, which assumed a three-quarters decrease in pollution.

Researchers examined data from onboard fuel consumption monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” said a senior researcher involved in the report. “That gap is growing and poses a serious issue. Consequently, PHEVs pollute almost as much as gasoline cars.”

Primary Factors Behind the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to total distance. They determined that just 27% of driving was completed in EV mode, whereas lab assumptions assumed 84%.

Even, when running in electric mode, pollution levels were well above official projections. That happened because electric motors were insufficiently powerful sufficient to function independently, leading to combustion motors using gasoline for almost a third of the travel covered in EV mode.

Regulatory and Financial Implications

Based on estimates, the underestimation of PHEV emissions allowed several large carmaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 more annually in operating costs than would be estimated under laboratory conditions.

“The bold claims that manufacturers often promote about their PHEV vehicles are clearly way off the mark,” commented a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy use, CO₂ production, and running expenses.”

Political Debate and Automotive Pressure

Hybrid cars have lately been brought back into political debates as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on new internal combustion cars in 2035 has faced heavy lobbying from the car industry and resistance from member states with large car manufacturing.

Several senior politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

An independent energy policy expert, who was not involved with the research, called the report a “very useful contribution” after years in which parts of the car sector claimed there was too little information to properly assess real-world CO2 output.

“The results demonstrate, beyond any doubt, that the difference between official and real-world PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional cars,” the expert stated. “All regulatory adjustments concerning PHEVs should be made with extreme care and in the light of this data.”