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Plug-in hybrid electric vehicles release nearly five times greater planet-heating pollution than lab-reported figures show, according to a new report.

Widening Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel vehicles, based on research conducted by a non-profit group. That differs significantly with laboratory estimates, which assumed a 75% reduction in emissions.

Analysts studied information from onboard energy use monitors of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team found that real-world CO₂ output 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,” stated a lead researcher participating in the report. “That gap is widening and poses a significant issue. As a result, PHEVs emit nearly as much as petrol vehicles.”

Primary Factors Behind the Discrepancy

Analysts linked most of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in battery mode compared to total mileage. The team determined that just a quarter of driving was completed in electric mode, whereas official assumptions suggested over four-fifths.

Even, when operating in EV mode, emission levels were well above lab estimates. That happened because electric motors were insufficiently powerful sufficient to function alone, resulting to engines burning gasoline for nearly one-third of the travel covered in electric mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV emissions enabled several large automaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay about €500 extra per year in operating expenses than is assumed under lab tests.

“The strong claims that automakers like to make about their PHEV vehicles are clearly far from the truth,” stated a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are little better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been brought again into political discussions as carmakers have lobbied the EU to relax CO₂ targets. A proposed ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with large car manufacturing.

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

One external energy economics specialist, who was unaffiliated with the study, called the report a “highly valuable contribution” after a long period in which segments of the car sector argued there was insufficient information to accurately evaluate actual CO2 output.

“These findings show, without question, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or diesel vehicles,” the expert stated. “All regulatory changes regarding PHEVs should be implemented with utmost care and in the light of this evidence.”