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Plug-in hybrid cars emit almost 5x greater global warming emissions than lab-reported figures indicate, according to a new report.

Widening Discrepancy In Lab and Real-World Emissions

Statistics shows that PHEVs emit only 19% less CO₂ than traditional gas and diesel vehicles, based on research conducted by a advocacy organization. That differs sharply with lab estimates, 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 emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” stated a lead analyst participating in the study. “This discrepancy is widening and poses a serious issue. Consequently, PHEVs pollute almost as much as petrol cars.”

Key Reasons Behind the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to total mileage. They determined that just 27% of travel was completed in electric mode, whereas lab estimates suggested over four-fifths.

Additionally, when running in EV mode, pollution amounts were well above lab estimates. This happened because EV motors were not strong sufficient to operate alone, leading to engines using gasoline for nearly a third of the travel completed in electric mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed four major automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay approximately €500 extra per year in running costs than is assumed under lab conditions.

“The bold claims that manufacturers like to make about their PHEV cars are obviously far from the truth,” commented a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Political Debate and Industry Pressure

Hybrid vehicles have recently been drawn again into political debates as automakers have lobbied the EU to weaken CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the car industry and resistance from member states with significant car industries.

Some senior politicians have proposed plug-in hybrids as a possible “flexibility” solution to include in the legislation.

An independent energy economics expert, who was not involved with the research, called the report a “very useful contribution” after a long period in which segments of the car industry argued there was too little data to properly assess actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap between lab and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or conventional cars,” the expert stated. “All policy changes regarding PHEVs should be made with utmost care and in the light of that evidence.”