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PHEVs release nearly five times more planet-heating emissions than official figures show, according to a recent analysis.

Widening Discrepancy In Official and Actual Emissions

Data reveals that PHEVs release only one-fifth lower CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a advocacy organization. This differs sharply with laboratory tests, which assumed a 75% reduction in pollution.

Researchers examined data from onboard fuel consumption monitors of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” said a senior researcher participating in the study. “This discrepancy is widening and poses a serious issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in battery mode relative to total distance. The team found that only a quarter of driving was done in EV mode, while official estimates suggested 84%.

Additionally, when operating in electric mode, pollution amounts were well above lab projections. This occurred because electric motors were not strong sufficient to function independently, leading to combustion motors burning 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 enabled several large automaker groups to avoid more than €5bn in fines between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 extra annually in running expenses than is estimated under laboratory tests.

“The bold claims that manufacturers like to make about their PHEV cars are obviously way off the truth,” stated a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and saving costs. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Automotive Pressure

Hybrid vehicles have lately been brought back into political debates as automakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from member states with large car industries.

Some senior officials have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the regulation.

An independent energy policy expert, who was not involved with the study, called the report a “highly valuable addition” after years in which parts of the car sector argued there was too little information to accurately assess real-world CO2 output.

“These findings show, beyond any doubt, that the difference in official and real-world PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel cars,” they stated. “All policy changes regarding PHEVs should be implemented with utmost caution and in the light of this data.”