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Plug-in hybrid electric vehicles release almost five times more planet-heating pollution than official data show, according to a recent report.

Widening Gap In Lab and Real-World CO2 Output

Statistics reveals that PHEVs emit just one-fifth less CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a advocacy organization. That differs significantly with laboratory tests, which assumed a 75% decrease in pollution.

Researchers studied data from in-vehicle energy use monitors of 800,000 vehicles registered in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” said a senior analyst involved in the study. “That discrepancy is widening and poses a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in electric mode compared to overall mileage. They found that only 27% of travel was done in electric mode, while lab assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution amounts were well above lab estimates. This occurred because electric motors were insufficiently powerful enough to function alone, leading to engines burning gasoline for almost one-third of the travel covered in electric mode.

Regulatory and Economic Implications

According to calculations, the underestimation of PHEV CO2 output enabled four large carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 more per year in operating expenses than would be estimated under lab conditions.

“The strong claims that automakers often promote about their PHEV vehicles are obviously way off the mark,” stated a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Political Debate and Automotive Lobbying

Hybrid vehicles have lately been drawn again into policy discussions as carmakers have pressed the EU to weaken CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with significant automotive industries.

Several high-level officials have suggested PHEVs as a potential “flexibility” solution to include in the regulation.

One external energy policy specialist, who was not involved with the research, called the analysis a “very useful addition” after years in which parts of the car sector claimed there was too little information to accurately evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional cars,” they said. “Any regulatory adjustments concerning PHEVs should be made with utmost care and in the light of this data.”