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Plug-in hybrid cars release nearly five times greater planet-heating emissions than lab-reported figures indicate, as per a new report.

Growing Gap Between Official and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than traditional gas and diesel cars, based on analysis conducted by a non-profit group. That differs sharply with laboratory estimates, which suggested a three-quarters decrease in pollution.

Analysts studied data from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a senior researcher participating in the study. “This gap is growing and poses a significant problem. Consequently, PHEVs pollute nearly as much as petrol cars.”

Key Factors Driving the Discrepancy

Researchers linked the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in electric mode relative to overall distance. The team found that just a quarter of driving was done in EV mode, while official assumptions assumed over four-fifths.

Additionally, when running in EV mode, pollution levels were well above lab projections. That happened because electric motors were not strong sufficient to operate alone, resulting to combustion motors burning gasoline for almost a third of the travel covered in EV mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output allowed several major carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend approximately €500 more annually in running expenses than would be estimated under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the truth,” commented a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been drawn back into policy debates as automakers have lobbied the EU to relax CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and opposition from EU countries with large automotive industries.

Several high-level politicians have proposed PHEVs as a possible “compromise” solution to include in the regulation.

One independent energy policy specialist, who was not involved with the research, described the analysis a “very useful addition” after years in which segments of the automotive sector claimed there was insufficient data to accurately assess actual emissions.

“The results demonstrate, without question, that the gap between official and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or diesel vehicles,” they stated. “Any regulatory changes concerning PHEVs should be made with extreme care and in the light of that evidence.”