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Plug-in hybrid electric vehicles emit almost five times greater global warming pollution than lab-reported data show, as per a new report.

Widening Discrepancy Between Lab and Actual CO2 Output

Statistics reveals that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis carried out by a non-profit group. That differs significantly with lab estimates, which suggested a 75% reduction in pollution.

Researchers studied information from onboard energy use monitors of eight hundred thousand vehicles registered in Europe from 2021 and 2023. The team discovered 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 emissions are rising, while lab-reported emissions are falling,” said a senior researcher participating in the study. “That discrepancy is widening and creates a significant problem. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Key Factors Behind the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery power relative to overall distance. They found that only 27% of driving was done in electric mode, while official estimates assumed over four-fifths.

Even, when operating in electric mode, emission amounts were well above lab estimates. This happened because electric motors were not strong enough to function independently, leading to combustion motors burning fossil fuels for nearly one-third of the distance completed in electric mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed four major automaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 more per year in operating expenses than is assumed under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are obviously far from the mark,” stated a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been brought again into policy debates as automakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with significant automotive industries.

Some senior officials have proposed plug-in hybrids as a possible “compromise” option to include in the regulation.

An external energy economics expert, who was unaffiliated with the research, called the analysis a “highly valuable contribution” after years in which parts of the car sector argued there was too little information to properly assess actual emissions.

“The results show, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional cars,” the expert stated. “All policy adjustments concerning PHEVs should be made with extreme care and considering this data.”