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Plug-in hybrid cars release almost 5x more global warming emissions than lab-reported data show, as per a recent analysis.

Growing Discrepancy In Lab and Real-World Emissions

Statistics reveals that PHEVs release just 19% lower CO₂ than traditional gas and diesel cars, according to analysis conducted by a non-profit organization. This contrasts sharply with lab tests, which suggested a three-quarters decrease in pollution.

Researchers studied information from in-vehicle energy use meters of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ output 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 lab-reported emissions are falling,” stated a senior researcher participating in the report. “That discrepancy is growing and creates a significant issue. Consequently, PHEVs emit nearly 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 ratio of kilometers travelled in battery power compared to overall mileage. They found that just a quarter of travel was done in EV mode, whereas official estimates assumed over four-fifths.

Additionally, when operating in EV mode, pollution amounts were well above official estimates. That occurred because EV motors were insufficiently powerful sufficient to operate independently, leading to engines using fossil fuels for nearly one-third of the travel covered in EV mode.

Regulatory and Financial Implications

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

Furthermore, owners of PHEVs could pay approximately €500 extra annually in running costs than would be assumed under laboratory tests.

“The strong statements that automakers like to make about their PHEV cars are obviously far from the truth,” commented a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought again into political discussions as carmakers have pressed the EU to weaken CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with large automotive industries.

Several high-level officials have proposed PHEVs as a potential “flexibility” option to include in the legislation.

An external energy policy expert, who was unaffiliated with the study, called the analysis a “very useful contribution” after years in which segments of the automotive industry claimed there was too little data to properly assess actual emissions.

“These findings demonstrate, without question, that the gap between official and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional cars,” the expert said. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of this data.”