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Plug-in hybrid cars emit nearly five times greater global warming pollution than lab-reported data show, according to a new report.

Widening Gap In Official and Real-World CO2 Output

Statistics reveals that PHEVs release only one-fifth less CO₂ than traditional gas and diesel vehicles, according to analysis conducted by a non-profit group. That differs significantly with laboratory tests, which assumed a three-quarters reduction in pollution.

Analysts examined data from in-vehicle fuel consumption meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” said a lead researcher involved in the report. “This gap is widening and creates a serious issue. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Researchers linked most of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in electric mode compared to total mileage. The team determined that only 27% of travel was done in EV mode, while lab estimates suggested over four-fifths.

Additionally, when operating in EV mode, emission amounts were well above official projections. This happened because electric motors were insufficiently powerful enough to function alone, leading to engines burning fossil fuels for almost a third of the distance covered in EV mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV CO2 output enabled four major carmaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in running expenses than would be assumed under lab conditions.

“The bold statements that manufacturers like to make about their PHEV cars are clearly way off the truth,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been drawn again into policy discussions as carmakers have lobbied the EU to relax CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and resistance from EU countries with large car manufacturing.

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

An independent energy economics specialist, who was not involved with the study, described the report a “very useful addition” after years in which segments of the car sector claimed there was insufficient data to accurately evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap between official and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert stated. “Any regulatory adjustments concerning PHEVs should be implemented with extreme caution and considering that data.”