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Plug-in hybrid cars produce almost five times greater planet-heating emissions than official data show, as per a new analysis.

Growing Discrepancy Between Official and Actual CO2 Output

Statistics shows that PHEVs release only 19% less CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. This differs significantly with laboratory estimates, which suggested a 75% decrease in emissions.

Researchers studied information from onboard energy use monitors of 800,000 vehicles registered in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are falling,” said a lead analyst participating in the study. “This gap is growing and poses a serious problem. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in electric mode relative to overall mileage. They found that only a quarter of driving was completed in electric mode, while official estimates suggested 84%.

Additionally, when operating in electric mode, pollution levels were well above official estimates. That occurred because EV motors were not strong sufficient to operate independently, resulting to engines burning fossil fuels for almost a third of the travel completed in electric mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output allowed several large automaker groups to avoid over €5bn in fines between 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 more per year in operating expenses than would be assumed under lab conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are only slightly improved than standard petrol and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Political Debate and Automotive Pressure

Hybrid cars have lately been drawn back into political debates as carmakers have pressed the European Union to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant automotive industries.

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

An independent energy policy expert, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the car industry argued there was too little information to properly assess actual CO2 output.

“The results show, beyond any doubt, that the gap in official and actual PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional cars,” the expert said. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of that data.”