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PHEVs release nearly 5x more global warming emissions than lab-reported data show, according to a new analysis.

Growing Gap Between Official and Real-World Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel vehicles, according to research carried out by a advocacy group. That differs significantly with laboratory tests, which suggested a three-quarters decrease in emissions.

Researchers examined data from in-vehicle energy use meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are falling,” stated a senior analyst participating in the report. “That gap is growing and creates a significant problem. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Primary Factors Driving the Discrepancy

Researchers linked most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in electric mode relative to total distance. The team found that only a quarter of driving was done in electric mode, while lab assumptions assumed over four-fifths.

Even, when running in electric mode, pollution levels were significantly higher than lab projections. This occurred because electric motors were insufficiently powerful sufficient to operate alone, resulting to engines burning gasoline for almost one-third of the travel covered in electric mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV emissions enabled four major carmaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ targets.

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

“The strong claims that manufacturers like to make about their PHEV vehicles are obviously way off the mark,” stated a transport analyst. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Lobbying

Hybrid cars have recently been brought again into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the car industry and opposition from member states with large car industries.

Some high-level officials have suggested PHEVs as a possible “flexibility” solution to include in the legislation.

One external energy policy specialist, who was unaffiliated with the research, described the analysis a “very useful contribution” after years in which parts of the car industry argued there was too little information to accurately assess real-world emissions.

“These findings show, without question, that the difference between official and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional cars,” the expert stated. “Any regulatory changes regarding PHEVs should be made with extreme caution and in the light of that data.”