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Plug-in hybrid electric vehicles emit nearly 5x greater global warming emissions than official data show, as per a new report.

Widening Gap In Lab and Actual Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, based on research conducted by a non-profit group. That differs sharply with laboratory tests, which assumed a three-quarters decrease in pollution.

Researchers examined data from in-vehicle energy use meters of eight hundred thousand cars registered in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Actual emissions are rising, while official emissions are falling,” said a senior researcher participating in the report. “That gap is widening and creates a serious problem. Consequently, PHEVs pollute nearly as much as petrol cars.”

Key Factors Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery mode relative to total distance. The team determined that just a quarter of travel was completed in EV mode, while lab assumptions suggested 84%.

Additionally, when operating in electric mode, emission levels were well above lab projections. That happened because electric motors were not strong sufficient to operate alone, leading to combustion motors using fossil fuels for nearly one-third of the distance covered in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV emissions allowed four major carmaker companies to escape over €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay approximately €500 more annually in running expenses than is estimated under laboratory conditions.

“The strong claims that manufacturers often promote about their PHEV vehicles are clearly far from the truth,” commented a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been brought again into political debates as carmakers have pressed the EU to relax CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and resistance from EU countries with large automotive manufacturing.

Some high-level politicians have suggested PHEVs as a possible “flexibility” solution to introduce in the regulation.

An independent energy economics expert, who was not involved with the research, called the report a “very useful addition” after a long period in which segments of the automotive industry claimed there was too little information to accurately assess actual emissions.

“These findings show, without question, that the difference between lab and actual PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” they said. “Any policy adjustments concerning PHEVs should be made with utmost care and considering that evidence.”