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Plug-in hybrid cars release almost 5x greater planet-heating pollution than lab-reported figures indicate, as per a new analysis.

Growing Gap In Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a non-profit organization. This differs significantly with lab tests, which assumed a three-quarters decrease in emissions.

Researchers examined information from onboard fuel consumption monitors of 800,000 vehicles sold in Europe between 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, up from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are decreasing,” said a lead analyst involved in the report. “That discrepancy is widening and creates a serious problem. As a result, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed most of the gap to overestimates of the “electric driving share” – the ratio of miles driven in battery mode relative to overall distance. The team determined that just a quarter of driving was done in EV mode, while official estimates suggested over four-fifths.

Additionally, when operating in EV mode, pollution amounts were well above lab projections. That happened because EV motors were not strong sufficient to operate alone, resulting to engines burning gasoline for nearly one-third of the distance completed in electric mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV CO2 output enabled several major carmaker groups to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 extra annually in running costs than is assumed under lab conditions.

“The strong statements that automakers often promote about their PHEV cars are obviously way off the mark,” commented a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been drawn back into political discussions as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on new combustion engine cars in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with large car industries.

Several senior officials have proposed PHEVs as a possible “compromise” option to introduce in the regulation.

One independent energy policy expert, who was unaffiliated with the research, called the report a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was too little data to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap in official and actual PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” they stated. “Any policy changes regarding PHEVs should be made with utmost care and in the light of that data.”