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Plug-in hybrid electric vehicles emit almost five times more planet-heating pollution than lab-reported data show, as per a new analysis.

Growing Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth lower CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy group. This contrasts sharply with laboratory tests, which assumed a three-quarters reduction in emissions.

Analysts studied data from onboard energy use monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” said a senior researcher participating in the study. “That discrepancy is growing and creates a significant issue. As a result, PHEVs pollute almost as heavily as petrol vehicles.”

Primary Factors Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in electric power relative to overall mileage. The team found that only a quarter of travel was completed in electric mode, while lab assumptions assumed 84%.

Even, when operating in electric mode, pollution levels were well above official projections. That happened because EV motors were not strong enough to function independently, leading to engines using gasoline for nearly one-third of the distance covered in EV mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV emissions enabled four major automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 more per year in running costs than would be estimated under lab tests.

“The bold claims that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving costs. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Political Discussion and Automotive Pressure

Hybrid cars have lately been drawn back into policy discussions as carmakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the car industry and opposition from EU countries with large car manufacturing.

Some senior politicians have proposed PHEVs as a possible “compromise” option to introduce in the legislation.

One external energy policy specialist, who was not involved with the research, described the analysis a “highly valuable addition” after a long period in which parts of the car industry argued there was too little data to properly evaluate actual emissions.

“The results show, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ output is significantly larger than for petrol or conventional cars,” the expert stated. “All regulatory adjustments concerning PHEVs should be implemented with extreme care and considering that evidence.”