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Plug-in hybrid electric vehicles release nearly 5x more global warming emissions than official data indicate, according to a recent report.

Widening Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% lower CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit organization. That contrasts significantly with lab tests, which assumed a 75% decrease in pollution.

Researchers examined information from in-vehicle energy use meters of 800,000 cars registered in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” said a senior analyst participating in the study. “This gap is growing and creates a serious problem. As a result, PHEVs pollute almost as much as petrol vehicles.”

Key Factors Behind the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in battery mode compared to total distance. The team found that only 27% of driving was done in electric mode, whereas official assumptions assumed over four-fifths.

Even, when running in EV mode, pollution amounts were significantly higher than official estimates. That occurred because electric motors were insufficiently powerful sufficient to operate alone, leading to combustion motors using gasoline for almost one-third of the travel covered in electric mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV emissions enabled several major carmaker groups to escape over €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay about €500 more annually in operating costs than is assumed under laboratory conditions.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are clearly way off the truth,” commented a automotive analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have recently been drawn back into political debates as automakers have lobbied the European Union to relax CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with large automotive manufacturing.

Several senior politicians have proposed PHEVs as a possible “flexibility” solution to introduce in the legislation.

An external energy policy specialist, who was not involved with the research, called the report a “very useful addition” after years in which segments of the automotive industry argued there was too little data to properly assess real-world CO2 output.

“These findings demonstrate, without question, that the difference in official and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” the expert said. “All regulatory adjustments regarding PHEVs should be made with utmost care and considering that evidence.”