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Plug-in hybrid electric vehicles produce almost five times more global warming pollution than lab-reported figures show, according to a new analysis.

Growing Gap Between Official and Actual Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than traditional gas and diesel vehicles, based on analysis conducted by a advocacy group. This differs significantly with laboratory tests, which assumed a three-quarters decrease in pollution.

Researchers examined information from onboard fuel consumption meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, increased from three and a half times in 2021.

“Real-world emissions are rising, while official figures are decreasing,” stated a senior analyst involved in the study. “This gap is growing and creates a significant problem. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Primary Reasons Behind the Discrepancy

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to total mileage. The team found that just a quarter of driving was completed in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when running in electric mode, emission amounts were well above lab projections. This happened because EV motors were not strong sufficient to operate independently, resulting to combustion motors using fossil fuels for almost a third of the distance covered in EV mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV CO2 output allowed four large carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay approximately €500 extra annually in running costs than is estimated under laboratory tests.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are clearly far from the mark,” stated a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Political Debate and Industry Lobbying

Hybrid cars have lately been brought back into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and opposition from EU countries with significant automotive industries.

Some senior officials have suggested PHEVs as a possible “flexibility” solution to include in the regulation.

An external energy policy specialist, who was not involved with the research, described the analysis a “very useful addition” after a long period in which segments of the automotive industry claimed there was insufficient data to properly assess actual emissions.

“The results demonstrate, without question, that the gap between lab and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” the expert said. “All policy adjustments regarding PHEVs should be implemented with utmost care and considering that data.”