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Plug-in hybrid electric vehicles emit almost five times greater global warming pollution than official figures show, according to a recent analysis.

Widening Discrepancy Between Lab and Real-World Emissions

Data shows that PHEVs release just 19% lower CO₂ than conventional petrol and diesel cars, based on analysis carried out by a non-profit organization. That contrasts significantly with laboratory estimates, which assumed a three-quarters decrease in pollution.

Researchers studied data from onboard energy use monitors of 800,000 vehicles sold in Europe from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” stated a senior researcher involved in the report. “This discrepancy is growing and poses a significant issue. As a result, PHEVs emit nearly as much as petrol cars.”

Primary Factors Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to total mileage. The team found that just 27% of travel was completed in EV mode, while lab estimates assumed 84%.

Additionally, when running in EV mode, pollution levels were significantly higher than official projections. This happened because EV motors were not strong enough to operate independently, leading to combustion motors burning fossil fuels for nearly one-third of the travel completed in EV mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV emissions allowed four large carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs would pay about €500 more per year in operating costs than is estimated under lab conditions.

“The strong statements that manufacturers often promote about their PHEV cars are clearly way off the mark,” commented a automotive analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and saving costs. In reality, PHEVs are little better than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Debate and Automotive Lobbying

Hybrid vehicles have recently been drawn again into political discussions as carmakers have lobbied the European Union to relax CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced intense pressure from the automotive industry and opposition from EU countries with large car industries.

Several high-level officials have proposed PHEVs as a possible “flexibility” solution to include in the regulation.

One external energy economics specialist, who was not involved with the research, called the report a “very useful contribution” after years in which segments of the automotive industry claimed there was insufficient information to accurately assess actual CO2 output.

“The results show, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel vehicles,” the expert said. “All policy adjustments regarding PHEVs should be made with extreme care and considering this evidence.”