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Plug-in hybrid cars release almost 5x greater planet-heating pollution than official data indicate, as per a new analysis.

Widening Gap Between Official and Real-World Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to research carried out by a non-profit group. That differs sharply with laboratory tests, which assumed a three-quarters reduction in pollution.

Analysts studied data from onboard fuel consumption monitors of eight hundred thousand cars sold in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” stated a lead analyst involved in the study. “That gap is growing and creates a significant problem. Consequently, PHEVs pollute almost as much as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric power compared to total distance. They found that only a quarter of driving was done in EV mode, while official assumptions suggested 84%.

Even, when running in EV mode, pollution amounts were well above lab estimates. That happened because EV motors were insufficiently powerful enough to operate alone, leading to combustion motors burning fossil fuels for nearly a third of the distance completed in electric mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV CO2 output enabled several large automaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra annually in operating expenses than is estimated under lab conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the truth,” commented a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy use, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Hybrid cars have lately been brought back into policy debates as automakers have pressed the EU to relax CO₂ targets. A planned ban on new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and opposition from member states with significant automotive industries.

Some high-level politicians have suggested PHEVs as a potential “compromise” solution to include in the regulation.

An independent energy policy specialist, who was not involved with the study, called the report a “very useful contribution” after a long period in which parts of the automotive sector argued there was insufficient data to properly assess real-world emissions.

“These findings demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel cars,” the expert stated. “All regulatory changes regarding PHEVs should be made with extreme caution and considering this evidence.”