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PHEVs release almost 5x greater planet-heating emissions than lab-reported data indicate, as per a new report.

Widening Gap In Lab and Real-World CO2 Output

Data shows that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit organization. That differs significantly with lab tests, which suggested a 75% decrease in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles registered in Europe from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” stated a lead analyst participating in the report. “That discrepancy is widening and creates a serious problem. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Primary Factors Behind the Discrepancy

Analysts linked most of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to total mileage. They 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 official projections. This happened because electric motors were insufficiently powerful enough to operate independently, resulting to engines using fossil fuels for nearly one-third of the travel covered in EV mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV emissions enabled four major automaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 more per year in operating expenses than is assumed under laboratory tests.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Political Debate and Automotive Pressure

Hybrid cars have lately been brought again into policy debates as automakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the car industry and resistance from member states with significant automotive manufacturing.

Several high-level officials have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

An independent energy economics specialist, who was unaffiliated with the study, called the report a “very useful contribution” after a long period in which segments of the car sector argued there was too little data to properly evaluate actual emissions.

“The results show, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or conventional cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with extreme caution and in the light of that data.”