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Plug-in hybrid electric vehicles emit almost five times greater planet-heating emissions than lab-reported figures indicate, according to a recent report.

Widening Gap Between Official and Actual Emissions

Statistics reveals that PHEVs emit only 19% lower CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a non-profit organization. This contrasts significantly with lab tests, which assumed a three-quarters decrease in pollution.

Researchers studied information from in-vehicle fuel consumption meters of eight hundred thousand cars sold in Europe from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” stated a senior analyst involved in the report. “This gap is widening and creates a serious issue. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Reasons Driving the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to overall mileage. The team determined that just a quarter of travel was completed in EV mode, while lab assumptions assumed 84%.

Even, when operating in EV mode, emission amounts were well above official estimates. That occurred because EV motors were not strong sufficient to operate alone, leading to combustion motors using gasoline for almost a third of the distance covered in electric mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV CO2 output allowed four major automaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 more annually in running costs than is estimated under lab tests.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are clearly far from the mark,” stated a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little better than regular petrol and diesel cars in terms of fuel use, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been drawn back into political debates as carmakers have pressed the European Union to weaken CO₂ targets. A proposed prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the car sector and opposition from member states with significant automotive manufacturing.

Some high-level officials have proposed PHEVs as a potential “flexibility” option to include in the regulation.

An independent energy policy specialist, who was unaffiliated with the study, described the report a “highly valuable contribution” after a long period in which segments of the automotive industry claimed there was too little information to accurately assess real-world emissions.

“These findings demonstrate, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional cars,” they said. “All policy changes regarding PHEVs should be implemented with extreme care and in the light of that data.”