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Plug-in hybrid cars emit nearly five times greater planet-heating pollution than lab-reported figures show, according to a recent analysis.

Growing Gap Between Official and Real-World CO2 Output

Data shows that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel cars, according to analysis conducted by a advocacy group. This contrasts significantly with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers studied information from in-vehicle energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” stated a senior researcher participating in the report. “That gap is widening and creates a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Key Factors Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “electric driving share” – the ratio of miles driven in battery mode relative to total mileage. They determined that only 27% of travel was done in electric mode, while lab estimates assumed over four-fifths.

Even, when operating in EV mode, emission amounts were significantly higher than official estimates. This happened because EV motors were insufficiently powerful sufficient to function alone, resulting to combustion motors burning fossil fuels for nearly one-third of the distance covered in electric mode.

Policy and Financial Implications

According to calculations, the underestimation of PHEV emissions enabled several major automaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could spend approximately €500 extra annually in operating costs than is assumed under lab tests.

“The bold statements that manufacturers like to make about their PHEV cars are clearly far from the mark,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been drawn again into policy debates as automakers have pressed the European Union to weaken CO₂ standards. A proposed ban on new combustion engine cars in 2035 has faced heavy lobbying from the car industry and opposition from EU countries with large car manufacturing.

Some senior politicians have suggested PHEVs as a possible “flexibility” option to introduce in the regulation.

One independent energy economics expert, who was not involved with the research, called the analysis a “very useful addition” after a long period in which parts of the automotive sector claimed there was too little data to accurately assess real-world CO2 output.

“The results demonstrate, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional cars,” they said. “Any policy changes regarding PHEVs should be made with extreme caution and in the light of that data.”