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Plug-in hybrid electric vehicles produce almost 5x more planet-heating emissions than official data indicate, as per a new report.

Widening Discrepancy Between Official and Actual CO2 Output

Data shows that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel cars, according to analysis conducted by a non-profit group. That differs significantly with laboratory tests, which assumed a 75% decrease in pollution.

Analysts examined data from in-vehicle energy use monitors of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” said a lead researcher participating in the report. “This discrepancy is growing and poses a significant issue. As a result, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Factors Behind the Emissions Gap

Researchers linked the majority of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in battery power compared to total mileage. They found that just a quarter of driving was completed in electric mode, whereas official estimates assumed 84%.

Additionally, when operating in electric mode, emission amounts were significantly higher than lab projections. That occurred because electric motors were insufficiently powerful enough to operate independently, leading to combustion motors burning fossil fuels for almost a third of the distance completed in electric mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV CO2 output enabled four large automaker companies to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would pay approximately €500 extra per year in running costs than is assumed under lab tests.

“The bold statements that manufacturers often promote about their PHEV cars are obviously way off the truth,” stated a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Lobbying

Hybrid vehicles have lately been drawn again into political discussions as automakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the automotive industry and opposition from member states with large car manufacturing.

Several senior officials have proposed PHEVs as a possible “compromise” solution to introduce in the regulation.

One external energy policy expert, who was unaffiliated with the research, described the analysis a “very useful contribution” after years in which segments of the automotive industry argued there was too little data to accurately assess actual CO2 output.

“These findings show, beyond any doubt, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or conventional vehicles,” the expert said. “Any regulatory changes regarding PHEVs should be made with extreme caution and considering that data.”