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Plug-in hybrid cars release almost 5x greater planet-heating emissions than official figures indicate, according to a new report.

Widening Gap Between Lab and Real-World Emissions

Statistics shows that PHEVs emit only 19% lower CO₂ than traditional gas and diesel cars, according to analysis conducted by a non-profit group. This contrasts sharply with lab estimates, which assumed a 75% reduction in emissions.

Researchers studied data from in-vehicle fuel consumption meters of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” said a lead analyst involved in the study. “This discrepancy is growing and creates a significant issue. As a result, PHEVs emit almost as much as petrol vehicles.”

Key Factors Driving the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the percentage of miles driven in battery mode compared to overall distance. The team found that only a quarter of travel was done in EV mode, whereas official assumptions assumed 84%.

Even, when running in electric mode, emission amounts were significantly higher than lab estimates. This happened because EV motors were not strong sufficient to function independently, leading to engines burning fossil fuels for almost one-third of the distance covered in EV mode.

Regulatory and Economic Implications

Based on estimates, the underestimation of PHEV emissions allowed several major carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would pay about €500 extra annually in operating expenses than is assumed under laboratory conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” commented a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are little improved than standard gas and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn again into policy debates as carmakers have pressed the European Union to relax CO₂ standards. A planned ban on new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and opposition from member states with significant car manufacturing.

Some senior officials have proposed PHEVs as a possible “flexibility” option to include in the legislation.

One external energy policy expert, who was not involved with the research, called the report a “highly valuable addition” after a long period in which segments of the automotive sector claimed there was insufficient data to accurately evaluate real-world emissions.

“These findings show, without question, that the difference in official and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or diesel cars,” they stated. “All policy changes concerning PHEVs should be made with utmost caution and in the light of this data.”