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Plug-in hybrid cars release nearly 5x more global warming emissions than official data indicate, as per a new report.

Widening Discrepancy In Official and Real-World Emissions

Data shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel cars, according to analysis conducted by a advocacy organization. That differs significantly with laboratory tests, which suggested a 75% reduction in emissions.

Analysts studied data from onboard fuel consumption meters of eight hundred thousand cars sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a lead researcher participating in the study. “That gap is growing and poses a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline vehicles.”

Key Reasons Behind the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the ratio of miles driven in battery mode relative to overall distance. They determined that just a quarter of travel was completed in electric mode, while official estimates assumed over four-fifths.

Additionally, when running in EV mode, pollution levels were significantly higher than official estimates. This happened because electric motors were insufficiently powerful sufficient to operate independently, leading to combustion motors using fossil fuels for almost a third of the travel covered in EV mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions allowed four major automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend about €500 extra annually in operating expenses than is estimated under laboratory conditions.

“The bold statements that automakers often promote about their PHEV cars are obviously way off the truth,” stated a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn back into policy debates as carmakers have pressed the EU to relax CO₂ standards. A proposed ban on new combustion engine cars in 2035 has faced intense lobbying from the car sector and resistance from member states with large car manufacturing.

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

One independent energy policy expert, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which parts of the automotive sector claimed there was insufficient data to properly evaluate actual emissions.

“The results show, without question, that the gap in official and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel vehicles,” the expert said. “All policy changes regarding PHEVs should be implemented with utmost caution and considering this evidence.”