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Plug-in hybrid cars release nearly 5x greater global warming pollution than lab-reported data show, according to a recent report.

Widening Discrepancy In Official and Actual Emissions

Statistics reveals that PHEVs emit only one-fifth lower CO₂ than traditional gas and diesel cars, based on research conducted by a advocacy organization. That differs significantly with laboratory tests, which suggested a three-quarters decrease in pollution.

Researchers examined information from onboard fuel consumption meters of 800,000 vehicles registered in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are decreasing,” said a senior analyst involved in the study. “That discrepancy is widening and creates a significant issue. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Primary Factors Behind the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in electric power compared to overall distance. They found that just 27% of driving was done in electric mode, whereas lab estimates assumed 84%.

Even, when operating in EV mode, pollution amounts were well above lab projections. This happened because EV motors were not strong sufficient to function independently, resulting to engines burning fossil fuels for nearly a third of the travel covered in electric mode.

Regulatory and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output enabled four large carmaker companies to escape over €5bn in fines from 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 more annually in operating costs than is estimated under lab tests.

“The bold statements that manufacturers often promote about their PHEV cars are clearly far from the mark,” stated a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the environment and saving money. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into political discussions as carmakers have pressed the EU to relax CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with significant car manufacturing.

Several senior officials have proposed plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

An independent energy policy specialist, who was unaffiliated with the research, described the report a “very useful contribution” after years in which segments of the automotive industry claimed there was too little data to accurately assess actual CO2 output.

“These findings show, without question, that the gap between official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert stated. “Any policy changes regarding PHEVs should be made with utmost care and in the light of that data.”