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Plug-in hybrid cars produce nearly 5x greater global warming emissions than official data indicate, according to a recent analysis.

Growing Discrepancy In Official and Actual Emissions

Data reveals that PHEVs emit just 19% less CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a advocacy organization. This contrasts sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Analysts studied information from in-vehicle energy use monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are decreasing,” said a lead researcher participating in the study. “That discrepancy is widening and creates a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Key Reasons Driving the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery mode compared to total mileage. They found that only 27% of travel was completed in EV mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab estimates. That happened because electric motors were insufficiently powerful sufficient to operate independently, leading to engines using gasoline for almost a third of the distance covered in electric mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV CO2 output allowed several large carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 extra annually in operating costs than would be estimated under lab conditions.

“The bold claims that manufacturers like to make about their plug-in hybrid cars are obviously way off the mark,” commented a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been brought again into political debates as automakers have lobbied the EU to relax CO₂ standards. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and opposition from member states with large automotive manufacturing.

Several high-level officials have suggested PHEVs as a possible “flexibility” solution to introduce in the legislation.

One external energy economics expert, who was not involved with the study, called the analysis a “highly valuable addition” after a long period in which parts of the car industry argued there was insufficient data to accurately evaluate actual emissions.

“The results show, without question, that the difference between official and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or conventional cars,” the expert said. “Any regulatory changes concerning PHEVs should be made with extreme care and considering that data.”