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Plug-in hybrid cars emit almost five times greater global warming pollution than lab-reported data show, as per a recent report.

Widening Discrepancy Between Official and Real-World CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy organization. That contrasts sharply with lab tests, which assumed a three-quarters decrease in emissions.

Researchers studied information from in-vehicle energy use monitors of 800,000 cars sold in the EU from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a senior researcher participating in the study. “This gap is growing and creates a serious issue. As a result, PHEVs pollute almost as much as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Analysts linked most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery power compared to total mileage. The team found that just 27% of driving was completed in electric mode, while official estimates assumed 84%.

Additionally, when running in EV mode, emission amounts were well above lab projections. That occurred because electric motors were not strong enough to operate alone, leading to combustion motors using fossil fuels for nearly a third of the distance covered in EV mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions enabled several major carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 extra annually in running expenses than would be assumed under lab conditions.

“The strong statements that automakers like to make about their plug-in hybrid cars are obviously way off the mark,” commented a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been brought again into political discussions as carmakers have pressed the EU to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and opposition from EU countries with large car manufacturing.

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

One independent energy policy expert, who was not involved with the research, called the analysis a “highly valuable contribution” after a long period in which parts of the automotive sector argued there was too little data to accurately assess actual emissions.

“These findings show, without question, that the gap in official and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel cars,” they stated. “Any policy adjustments concerning PHEVs should be implemented with extreme care and in the light of this evidence.”