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Plug-in hybrid electric vehicles produce almost 5x greater planet-heating emissions than lab-reported data show, as per a new report.

Widening Gap Between Lab and Actual CO2 Output

Statistics reveals that PHEVs release only 19% lower CO₂ than conventional gas and diesel vehicles, based on research conducted by a advocacy group. This differs significantly with lab estimates, which assumed a 75% decrease in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official figures are decreasing,” stated a senior analyst involved in the study. “That discrepancy is widening and creates a significant issue. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the gap to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to overall distance. The team determined that only a quarter of driving was completed in EV mode, whereas lab estimates assumed 84%.

Even, when operating in EV mode, emission levels were significantly higher than official projections. This occurred because electric motors were insufficiently powerful sufficient to function alone, leading to combustion motors using fossil fuels for almost a third of the travel covered in EV mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions enabled four large carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs would pay approximately €500 more per year in operating costs than would be assumed under lab tests.

“The strong statements that manufacturers often promote about their PHEV cars are obviously far from the truth,” stated a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Political Discussion and Industry Lobbying

Hybrid vehicles have recently been drawn back into policy discussions as automakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from member states with large automotive manufacturing.

Several senior politicians have proposed PHEVs as a potential “flexibility” solution to include in the legislation.

An external energy policy expert, who was unaffiliated with the study, called the analysis a “highly valuable contribution” after years in which segments of the automotive industry argued there was too little information to accurately assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” they said. “All regulatory changes regarding PHEVs should be made with utmost care and considering that evidence.”