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Plug-in hybrid electric vehicles release almost 5x greater global warming pollution than lab-reported data indicate, according to a recent analysis.

Widening Gap Between Official and Real-World CO2 Output

Data shows that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel vehicles, according to research carried out by a advocacy group. That contrasts significantly with lab estimates, which assumed a three-quarters decrease in emissions.

Analysts studied data 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 nearly five times higher than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” said a lead researcher participating in the study. “This gap is widening and creates a serious problem. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Primary Factors Driving the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in electric mode compared to total distance. They determined that just a quarter of travel was done in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when operating in EV mode, pollution levels were well above lab projections. This happened because EV motors were insufficiently powerful enough to function alone, resulting to combustion motors using gasoline for almost a third of the travel covered in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV emissions allowed several large automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 extra per year in operating costs than would be assumed under laboratory conditions.

“The strong claims that manufacturers often promote about their PHEV cars are obviously way off the mark,” commented a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Pressure

Hybrid cars have lately been brought back into political discussions as automakers have pressed the European Union to relax CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with significant automotive industries.

Some senior politicians have proposed plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

One independent energy economics expert, who was not involved with the study, called the analysis a “highly valuable addition” after years in which parts of the automotive sector claimed there was too little information to properly evaluate actual emissions.

“These findings demonstrate, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel cars,” the expert stated. “Any policy adjustments regarding PHEVs should be implemented with utmost care and considering this evidence.”