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Plug-in hybrid cars produce nearly five times greater planet-heating emissions than official data indicate, according to a recent report.

Growing Discrepancy Between Official and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel vehicles, based on research conducted by a non-profit group. This contrasts significantly with lab tests, which suggested a three-quarters decrease in pollution.

Researchers studied data from onboard energy use monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” stated a lead researcher involved in the study. “That gap is growing and creates a significant issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Primary Factors Driving the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the ratio of miles travelled in battery power relative to overall mileage. They found that only 27% of travel was completed in electric mode, while lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, pollution amounts were well above lab projections. This occurred because EV motors were not strong enough to function independently, resulting to combustion motors using fossil fuels for nearly one-third of the travel covered in EV mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV CO2 output allowed four major automaker groups to escape over €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could spend approximately €500 more per year in operating expenses than is estimated under lab conditions.

“The strong statements that manufacturers like to make about their PHEV vehicles are obviously way off the mark,” stated a automotive analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are little better than standard petrol and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Policy Debate and Industry Pressure

Hybrid cars have recently been brought back into political debates as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive sector and resistance from member states with large automotive manufacturing.

Several high-level officials have proposed plug-in hybrids as a potential “compromise” option to include in the legislation.

An external energy economics specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive industry claimed there was too little data to properly assess actual CO2 output.

“These findings show, without question, that the gap in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel cars,” the expert stated. “All policy adjustments concerning PHEVs should be made with extreme care and in the light of this evidence.”