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PHEVs release nearly five times greater global warming emissions than lab-reported figures indicate, according to a new analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a advocacy group. This differs significantly with lab tests, which assumed a three-quarters reduction in pollution.

Researchers examined data from onboard energy use monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are falling,” stated a lead researcher involved in the report. “That gap is growing and poses a significant issue. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Reasons Behind the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of miles driven in electric mode relative to overall distance. They determined that just 27% of driving was done in EV mode, whereas official assumptions suggested over four-fifths.

Even, when operating in EV mode, pollution amounts were significantly higher than official estimates. This happened because EV motors were insufficiently powerful enough to operate alone, leading to combustion motors using fossil fuels for nearly one-third of the distance covered in EV mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV CO2 output allowed several major carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs could spend about €500 extra annually in running expenses than would be estimated under laboratory tests.

“The bold statements that automakers often promote about their PHEV cars are obviously way off the mark,” commented a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving money. In reality, PHEVs are little better than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Policy Debate and Automotive Pressure

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

Several high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

An independent energy economics specialist, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which parts of the automotive sector claimed there was too little data to properly assess actual emissions.

“These findings demonstrate, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much larger than for petrol or conventional cars,” they said. “All policy changes concerning PHEVs should be implemented with utmost care and considering that evidence.”