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Plug-in hybrid electric vehicles produce almost five times more global warming emissions than official figures indicate, according to a recent analysis.

Widening Gap In Lab and Actual Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel vehicles, based on research carried out by a non-profit group. This differs significantly with laboratory tests, which assumed a three-quarters decrease in emissions.

Researchers examined data from in-vehicle fuel consumption monitors of 800,000 cars registered in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are falling,” stated a senior researcher involved in the study. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Reasons Driving the Discrepancy

Analysts linked the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to total distance. The team found that just a quarter of driving was completed in EV mode, whereas lab estimates suggested over four-fifths.

Even, when running in EV mode, pollution amounts were well above official estimates. This happened because EV motors were not strong sufficient to operate independently, resulting to engines using gasoline for nearly a third of the travel completed in EV mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV emissions enabled several large carmaker groups to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 more annually in running expenses than is assumed under laboratory conditions.

“The bold statements that manufacturers like to make about their PHEV cars are clearly far from the truth,” commented a automotive analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been brought back into policy discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced heavy pressure from the car industry and opposition from member states with significant car manufacturing.

Several high-level politicians have proposed plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

One independent energy policy expert, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which segments of the car industry argued there was too little data to properly evaluate real-world CO2 output.

“The results demonstrate, without question, that the difference between official and actual PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel vehicles,” they stated. “All policy adjustments concerning PHEVs should be made with utmost caution and in the light of that evidence.”