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Plug-in hybrid cars release nearly 5x more global warming emissions than lab-reported figures show, according to a recent report.

Growing Discrepancy Between Official and Actual Emissions

Data reveals that PHEVs emit only 19% less CO₂ than traditional gas and diesel vehicles, based on analysis carried out by a non-profit organization. This differs sharply with laboratory tests, which assumed a 75% reduction in pollution.

Analysts examined data from onboard energy use meters of eight hundred thousand vehicles registered in Europe from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” said a lead analyst participating in the study. “This gap is growing and poses a significant issue. Consequently, PHEVs pollute nearly as much as gasoline vehicles.”

Key Factors Driving the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “electric driving share” – the percentage of miles driven in battery power relative to overall mileage. They found that just a quarter of driving was completed in EV mode, while official estimates assumed over four-fifths.

Even, when operating in electric mode, pollution amounts were well above official projections. This happened because electric motors were not strong enough to operate independently, resulting to engines burning fossil fuels for almost a third of the travel completed in EV mode.

Policy and Economic Implications

Based on calculations, the underestimation of PHEV emissions enabled four large carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 more annually in operating costs than is estimated under laboratory tests.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are clearly far from the truth,” stated a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are little better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been drawn again into policy debates as automakers have lobbied the European Union to relax CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with large automotive industries.

Some senior officials have suggested plug-in hybrids as a possible “compromise” solution to introduce in the legislation.

One independent energy economics specialist, who was unaffiliated with the research, called the report a “highly valuable addition” after years in which segments of the automotive industry argued there was too little data to accurately assess real-world emissions.

“The results demonstrate, without question, that the gap between official and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel cars,” they said. “All policy changes regarding PHEVs should be made with utmost caution and considering this evidence.”