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Plug-in hybrid electric vehicles release almost five times greater planet-heating pollution than lab-reported figures indicate, according to a recent report.

Growing Gap In Lab and Real-World Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a advocacy organization. That contrasts sharply with lab tests, which assumed a three-quarters decrease in emissions.

Analysts examined data from in-vehicle energy use monitors of 800,000 vehicles sold in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” stated a lead analyst participating in the study. “This gap is widening and poses a significant problem. As a result, PHEVs pollute nearly as much as gasoline cars.”

Key Factors Behind the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to total mileage. The team determined that just a quarter of travel was done in electric mode, while official estimates suggested over four-fifths.

Even, when running in electric mode, emission levels were significantly higher than lab projections. That occurred because EV motors were not strong sufficient to function alone, leading to engines burning fossil fuels for nearly a third of the travel completed in EV mode.

Regulatory and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed several major automaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 more per year in running expenses than is estimated under lab tests.

“The strong statements that automakers often promote about their PHEV cars are clearly way off the mark,” commented a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into political debates as automakers have pressed the European Union to relax CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with large car manufacturing.

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

An independent energy policy specialist, who was unaffiliated with the study, described the analysis a “very useful addition” after years in which segments of the automotive industry argued there was insufficient data to accurately assess real-world CO2 output.

“The results show, without question, that the gap in lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel cars,” they said. “All regulatory changes concerning PHEVs should be made with extreme care and in the light of that evidence.”