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PHEVs emit almost 5x more global warming pollution than lab-reported figures indicate, according to a new analysis.

Widening Gap Between Lab and Real-World Emissions

Data shows that PHEVs release only 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a advocacy organization. That differs significantly with laboratory tests, which assumed a 75% decrease in pollution.

Analysts studied information from onboard energy use monitors of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while official figures are falling,” said a senior researcher participating in the study. “That gap is growing and creates a serious problem. As a result, PHEVs emit almost as much as petrol cars.”

Key Reasons Driving the Discrepancy

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery mode compared to overall distance. The team determined that just 27% of driving was completed in EV mode, while official assumptions suggested over four-fifths.

Additionally, when running in electric mode, emission amounts were significantly higher than official projections. This occurred because EV motors were not strong enough to operate independently, resulting to engines burning gasoline for nearly a third of the travel covered in electric mode.

Policy and Economic Consequences

According to calculations, the lowballing of PHEV emissions allowed four large carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra annually in running expenses than is estimated under lab conditions.

“The bold statements that manufacturers often promote about their PHEV cars are obviously way off the truth,” commented a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than standard petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have recently been drawn again into political discussions as automakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced intense pressure from the car industry and opposition from EU countries with large car industries.

Several senior officials have proposed PHEVs as a potential “compromise” option to introduce in the regulation.

An external energy policy specialist, who was not involved with the research, called the report a “highly valuable addition” after a long period in which parts of the automotive sector argued there was too little information to accurately assess actual emissions.

“These findings show, without question, that the difference in lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional cars,” the expert stated. “All regulatory changes concerning PHEVs should be made with utmost care and considering that evidence.”