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Plug-in hybrid electric vehicles release nearly 5x greater planet-heating pollution than lab-reported figures indicate, according to a new report.

Widening Gap In Official and Actual Emissions

Statistics reveals that PHEVs emit only one-fifth lower CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a non-profit organization. That differs sharply with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers studied data from in-vehicle fuel consumption meters of 800,000 cars registered in the EU from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a senior researcher involved in the report. “That discrepancy is growing and poses a serious problem. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked most of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to total distance. They determined that only 27% of driving was completed in electric mode, while official estimates assumed over four-fifths.

Additionally, when operating in electric mode, emission amounts were well above lab projections. This happened because EV motors were insufficiently powerful sufficient to operate independently, resulting to engines burning gasoline for nearly one-third of the distance completed in electric mode.

Regulatory and Economic Implications

According to estimates, the lowballing of PHEV CO2 output enabled several large carmaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 extra annually in operating costs than would be estimated under lab conditions.

“The strong claims that automakers like to make about their plug-in hybrid cars are clearly far from the truth,” stated a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy use, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into policy discussions as automakers have pressed the European Union to weaken CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with large car industries.

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

One independent energy policy specialist, who was unaffiliated with the study, described the report a “highly valuable contribution” after years in which segments of the automotive industry claimed there was too little data to accurately evaluate real-world CO2 output.

“The results show, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or diesel cars,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with utmost caution and in the light of that data.”