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Plug-in hybrid electric vehicles emit almost 5x more global warming emissions than official data show, according to a new report.

Widening Gap In Official and Actual Emissions

Data shows that PHEVs release only 19% lower CO₂ than conventional gas and diesel cars, based on analysis conducted by a non-profit group. That contrasts sharply with lab estimates, which suggested a 75% decrease in pollution.

Researchers examined information from in-vehicle energy use meters of 800,000 cars sold in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are falling,” stated a senior researcher participating in the study. “This gap is growing and creates a significant problem. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Key Reasons Driving the Discrepancy

Analysts linked most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power relative to overall mileage. The team found that just 27% of driving was completed in EV mode, while official estimates suggested 84%.

Even, when running in electric mode, emission levels were well above lab projections. That occurred because EV motors were insufficiently powerful sufficient to operate alone, leading to combustion motors burning fossil fuels for nearly one-third of the travel covered in EV mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed several major carmaker companies to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay about €500 more annually in running costs than is estimated under lab conditions.

“The strong claims that automakers like to make about their PHEV cars are clearly way off the mark,” stated a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have lately been brought again into political debates as automakers have lobbied the EU to relax CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with significant car manufacturing.

Several senior officials have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

An external energy economics expert, who was unaffiliated with the research, described the report a “very useful contribution” after a long period in which segments of the automotive industry claimed there was too little information to accurately assess real-world emissions.

“These findings show, without question, that the difference between lab and real-world PHEV energy use and CO₂ output is significantly greater than for petrol or diesel vehicles,” the expert said. “Any policy changes concerning PHEVs should be implemented with extreme caution and considering that evidence.”