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Plug-in hybrid cars release nearly five times more planet-heating emissions than official figures indicate, according to a new analysis.

Widening Discrepancy In Lab and Real-World Emissions

Statistics reveals that PHEVs emit just one-fifth lower CO₂ than conventional petrol and diesel cars, according to research conducted by a advocacy group. This differs sharply with laboratory tests, which assumed a three-quarters reduction in pollution.

Researchers examined data from onboard energy use meters of 800,000 vehicles registered in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are decreasing,” said a senior researcher involved in the report. “This discrepancy is growing and poses a significant issue. As a result, PHEVs emit nearly as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Researchers linked most of the difference to overestimates of the “utility factor” – the percentage of miles travelled in battery power compared to overall mileage. They found that just a quarter of driving was done in EV mode, whereas official assumptions assumed over four-fifths.

Even, when running in electric mode, pollution amounts were well above official projections. This happened because electric motors were not strong sufficient to function independently, resulting to combustion motors using gasoline for nearly a third of the travel covered in electric mode.

Regulatory and Economic Consequences

Based on calculations, the lowballing of PHEV emissions allowed four major automaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could spend about €500 extra annually in running costs than would be assumed under lab tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought again into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the car industry and opposition from member states with large automotive manufacturing.

Some senior officials have suggested plug-in hybrids as a possible “compromise” option to introduce in the regulation.

One external energy economics specialist, who was unaffiliated with the study, called the report a “very useful contribution” after years in which parts of the automotive sector argued there was insufficient data to properly evaluate actual CO2 output.

“These findings show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with extreme caution and in the light of that data.”