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

Growing Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel cars, based on analysis carried out by a non-profit group. This differs sharply with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts examined data from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” stated a senior researcher involved in the study. “This gap is widening and creates a significant issue. Consequently, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “utility factor” – the ratio of miles driven in battery mode compared to overall mileage. The team found that only a quarter of driving was done in electric mode, whereas official estimates assumed 84%.

Additionally, when running in EV mode, emission amounts were well above lab projections. That happened because electric motors were not strong enough to function alone, leading to combustion motors using gasoline for almost one-third of the travel covered in electric mode.

Regulatory and Economic Implications

According to estimates, the lowballing of PHEV emissions enabled several large automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Additionally, owners of PHEVs would pay about €500 more annually in operating costs than would be estimated under lab conditions.

“The strong claims that automakers like to make about their PHEV cars are obviously far from the truth,” stated a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn again into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A planned prohibition on new internal combustion cars in 2035 has faced intense lobbying from the car industry and resistance from EU countries with significant car industries.

Several high-level officials have proposed plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

One independent energy policy expert, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which segments of the car industry claimed there was insufficient information to accurately assess real-world CO2 output.

“The results show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional cars,” they stated. “All policy adjustments regarding PHEVs should be made with utmost care and considering that data.”