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PHEVs release almost five times greater planet-heating emissions than official data indicate, according to a new analysis.

Growing Gap In Official and Real-World CO2 Output

Data shows that PHEVs emit just 19% less CO₂ than conventional petrol and diesel cars, based on analysis carried out by a non-profit organization. This differs significantly with lab estimates, which assumed a 75% reduction in pollution.

Researchers studied information from in-vehicle energy use meters of 800,000 vehicles registered in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” said a senior researcher participating in the report. “This discrepancy is growing and creates a significant issue. Consequently, PHEVs emit almost as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric power relative to overall distance. The team determined that only a quarter of driving was completed in electric mode, whereas official estimates suggested over four-fifths.

Additionally, when operating in electric mode, emission levels were well above official estimates. This occurred because electric motors were insufficiently powerful enough to function alone, leading to engines using gasoline for almost a third of the travel covered in electric mode.

Policy and Financial Consequences

According to calculations, the lowballing of PHEV emissions allowed four major automaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 more per year in operating costs than is assumed under laboratory tests.

“The strong claims that automakers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a automotive analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Discussion and Industry Pressure

Hybrid vehicles have recently been drawn back into policy debates as automakers have pressed the European Union to weaken CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and opposition from member states with large automotive industries.

Several senior officials have suggested plug-in hybrids as a possible “flexibility” option to include in the legislation.

An external energy policy specialist, who was not involved with the study, described the analysis a “very useful addition” after a long period in which segments of the car sector claimed there was insufficient information to properly assess actual emissions.

“These findings show, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is much, much greater than for petrol or conventional vehicles,” they said. “All policy adjustments regarding PHEVs should be made with extreme caution and in the light of that evidence.”