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Plug-in hybrid cars emit nearly five times more planet-heating pollution than official data show, according to a recent report.

Growing Discrepancy In Lab and Real-World Emissions

Statistics shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel vehicles, according to research conducted by a non-profit group. That contrasts significantly with lab estimates, which suggested a three-quarters reduction in emissions.

Analysts examined data from in-vehicle energy use meters of eight hundred thousand cars registered in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a lead researcher participating in the study. “That gap is growing and creates a serious problem. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Primary Factors Behind the Emissions Gap

Analysts linked most of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to total mileage. The team found that just 27% of travel was completed in EV mode, whereas official estimates suggested over four-fifths.

Even, when running in EV mode, emission levels were well above lab projections. This happened because electric motors were insufficiently powerful enough to operate alone, leading to combustion motors burning fossil fuels for almost one-third of the distance completed in EV mode.

Regulatory and Economic Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed several large automaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 more per year in running costs than would be estimated under laboratory tests.

“The bold statements that manufacturers like to make about their PHEV vehicles are obviously way off the truth,” stated a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are little improved than standard gas and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid vehicles have recently been drawn back into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with significant automotive manufacturing.

Some high-level politicians have suggested PHEVs as a possible “flexibility” option to introduce in the regulation.

An external energy economics specialist, who was not involved with the study, called the analysis a “highly valuable contribution” after a long period in which parts of the car industry argued there was too little information to accurately evaluate actual CO2 output.

“The results show, without question, that the gap in lab and real-world PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional vehicles,” they said. “Any policy changes concerning PHEVs should be implemented with utmost care and in the light of this evidence.”