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Plug-in hybrid electric vehicles produce almost five times more global warming emissions than lab-reported figures show, as per a recent analysis.

Widening Discrepancy In Lab and Real-World Emissions

Data shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel vehicles, according to research carried out by a non-profit group. That contrasts sharply with lab tests, which suggested a 75% decrease in emissions.

Analysts examined data from onboard fuel consumption monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while official figures are decreasing,” said a senior researcher involved in the study. “This discrepancy is widening and creates a significant problem. Consequently, PHEVs emit nearly as much as petrol cars.”

Key Reasons Driving the Discrepancy

Researchers attributed most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric power relative to total distance. The team determined that just a quarter of driving was done in EV mode, whereas lab estimates assumed 84%.

Additionally, when running in EV mode, pollution amounts were well above official projections. That occurred because electric motors were insufficiently powerful sufficient to operate alone, resulting to engines using gasoline for almost a third of the travel completed in EV mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV emissions allowed several major carmaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 extra annually in operating expenses than is assumed under lab tests.

“The strong claims that automakers often promote about their PHEV cars are clearly far from the truth,” commented a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn back into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and resistance from member states with large automotive manufacturing.

Some high-level politicians have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the legislation.

An independent energy economics expert, who was unaffiliated with the research, described the report a “very useful addition” after a long period in which parts of the automotive industry argued there was too little data to accurately evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or diesel cars,” the expert said. “All policy adjustments concerning PHEVs should be implemented with utmost caution and in the light of this evidence.”