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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating emissions than official data show, as per a new analysis.

Growing Discrepancy Between Official and Actual CO2 Output

Data shows that PHEVs release just 19% less CO₂ than traditional gas and diesel cars, based on research conducted by a non-profit group. This contrasts sharply with laboratory tests, which assumed a three-quarters reduction in pollution.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 vehicles sold in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Actual emissions are rising, while official figures are falling,” stated a senior researcher involved in the study. “That discrepancy is widening and poses a serious problem. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in electric power compared to total mileage. The team found that only a quarter of travel was done in electric mode, whereas official estimates assumed 84%.

Additionally, when operating in electric mode, emission amounts were well above official projections. That happened because EV motors were not strong enough to operate alone, leading to engines using fossil fuels for nearly one-third of the travel completed in EV mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV emissions allowed four major carmaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 more per year in operating expenses than would be assumed under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid cars are clearly way off the mark,” stated a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have recently been brought back into policy discussions as carmakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and opposition from member states with significant automotive industries.

Several high-level politicians have suggested PHEVs as a possible “flexibility” option to include in the regulation.

An independent energy economics expert, who was not involved with the study, called the report a “very useful addition” after a long period in which parts of the automotive industry claimed there was too little information to properly assess actual emissions.

“These findings show, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional cars,” they said. “All policy changes concerning PHEVs should be implemented with utmost caution and considering that data.”