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Plug-in hybrid cars produce almost five times greater global warming emissions than official data indicate, as per a new analysis.

Growing Gap In Official and Actual Emissions

Data shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy group. This contrasts significantly with lab tests, which suggested a 75% decrease in emissions.

Analysts examined information from onboard fuel consumption meters of 800,000 cars registered in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported figures are decreasing,” stated a lead analyst participating in the study. “This discrepancy is growing and poses a significant problem. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Key Factors Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in battery power compared to overall mileage. They found that just a quarter of travel was completed in electric mode, whereas official estimates assumed 84%.

Additionally, when running in EV mode, emission amounts were significantly higher than official projections. That happened because EV motors were insufficiently powerful sufficient to function independently, leading to engines using fossil fuels for almost one-third of the distance covered in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV emissions allowed several major carmaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs could spend about €500 more per year in operating costs than would be assumed under laboratory tests.

“The strong claims that automakers often promote about their plug-in hybrid vehicles are clearly way off the mark,” stated a transport analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have lately been drawn back into political debates as carmakers have pressed the EU to relax CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and resistance from member states with large automotive industries.

Some high-level politicians have suggested PHEVs as a possible “flexibility” solution to include in the legislation.

An external energy economics expert, who was not involved with the research, called the analysis a “highly valuable contribution” after a long period in which parts of the car industry claimed there was insufficient information to accurately evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” the expert said. “All regulatory adjustments concerning PHEVs should be made with extreme care and in the light of that data.”