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Plug-in hybrid cars release almost five times greater global warming emissions than lab-reported data show, according to a new analysis.

Growing Gap Between Lab and Real-World Emissions

Data shows that PHEVs release just 19% lower CO₂ than conventional gas and diesel vehicles, based on research conducted by a advocacy group. That contrasts sharply with laboratory tests, which assumed a three-quarters decrease in emissions.

Analysts studied information from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a senior analyst involved in the report. “That gap is widening and creates a significant problem. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Behind the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to total mileage. The team found that just a quarter of travel was done in electric mode, whereas lab estimates suggested 84%.

Even, when operating in EV mode, pollution amounts were significantly higher than official projections. This happened because EV motors were insufficiently powerful enough to function alone, resulting to engines using fossil fuels for nearly one-third of the distance covered in EV mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV CO2 output allowed four major carmaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs would pay about €500 extra annually in running expenses than is estimated under laboratory conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” stated a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Plug-in hybrid cars have recently been drawn back into political debates as automakers have lobbied the European Union to relax CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and resistance from member states with large automotive manufacturing.

Some senior officials have suggested PHEVs as a potential “compromise” option to include in the regulation.

An external 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 car industry argued there was insufficient information to accurately assess actual emissions.

“The results demonstrate, without question, that the difference between official and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional cars,” the expert said. “All policy changes regarding PHEVs should be made with utmost caution and in the light of this evidence.”