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Plug-in hybrid cars emit nearly five times greater global warming emissions than lab-reported figures indicate, according to a new analysis.

Growing Gap Between Lab and Actual Emissions

Statistics reveals that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel cars, according to analysis carried out by a advocacy organization. That differs sharply with laboratory estimates, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use meters of eight hundred thousand cars registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, up from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” said a senior researcher participating in the study. “That gap is growing and creates a serious problem. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Behind the Discrepancy

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode compared to total distance. They determined that only a quarter of travel was completed in electric mode, while lab assumptions assumed 84%.

Additionally, when running in EV mode, pollution amounts were well above lab estimates. This occurred because EV motors were insufficiently powerful sufficient to function alone, leading to combustion motors burning fossil fuels for nearly a third of the distance covered in electric mode.

Policy and Economic Consequences

According to calculations, the lowballing of PHEV emissions enabled several major carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs would spend about €500 more annually in operating costs than is assumed under laboratory conditions.

“The strong claims that automakers like to make about their PHEV vehicles are obviously way off the mark,” commented a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little better than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Pressure

Hybrid cars have recently been drawn again into policy discussions as automakers have pressed the EU to relax CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and opposition from EU countries with significant car industries.

Several senior politicians have proposed plug-in hybrids as a potential “flexibility” option to introduce in the legislation.

One independent energy policy specialist, who was unaffiliated with the study, described the analysis a “very useful contribution” after years in which parts of the automotive sector argued there was insufficient data to properly evaluate real-world CO2 output.

“These findings show, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel cars,” the expert stated. “All regulatory changes concerning PHEVs should be implemented with utmost care and in the light of that evidence.”