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PHEVs release nearly five times more global warming pollution than lab-reported figures show, according to a new report.

Widening Discrepancy In Lab and Real-World CO2 Output

Data reveals that PHEVs release just 19% less CO₂ than conventional gas and diesel vehicles, based on research conducted by a non-profit organization. That contrasts significantly with lab estimates, which assumed a three-quarters decrease in pollution.

Researchers examined information from in-vehicle fuel consumption meters of 800,000 vehicles registered in Europe between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, up from three and a half times in 2021.

“Actual emissions are rising, while official figures are falling,” said a lead analyst participating in the report. “This discrepancy is growing and creates a serious problem. As a result, PHEVs emit nearly as much as petrol cars.”

Key Reasons Behind the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric power compared to total mileage. They found that only 27% of driving was done in EV mode, while lab assumptions assumed over four-fifths.

Additionally, when operating in electric mode, pollution amounts were well above lab projections. This occurred because electric motors were not strong sufficient to operate independently, resulting to engines burning gasoline for almost one-third of the travel completed in EV mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV emissions allowed four large carmaker companies to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay about €500 extra per year in operating expenses than is estimated under laboratory conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than regular gas and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Political Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn again into political debates as automakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and resistance from member states with large automotive manufacturing.

Several senior politicians have suggested PHEVs as a possible “compromise” solution to include in the regulation.

One independent energy economics specialist, who was unaffiliated with the research, described the analysis a “highly valuable addition” after years in which segments of the automotive industry claimed there was insufficient data to properly evaluate actual CO2 output.

“The results show, without question, that the difference between official and real-world PHEV energy use and CO₂ emissions is much, much greater than for gasoline or diesel cars,” the expert said. “All policy changes concerning PHEVs should be made with extreme caution and in the light of this data.”