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Plug-in hybrid electric vehicles produce nearly 5x more global warming pollution than official figures show, according to a new report.

Growing Gap In Lab and Actual CO2 Output

Statistics reveals that PHEVs release just 19% less CO₂ than conventional gas and diesel vehicles, according to research carried out by a non-profit organization. That differs significantly with lab tests, which suggested a 75% decrease in pollution.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 vehicles sold in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” stated a lead researcher participating in the study. “This gap is widening and poses a serious problem. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Primary Reasons Behind the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers travelled in battery mode compared to total mileage. The team found that only a quarter of travel was done in EV mode, whereas official assumptions assumed over four-fifths.

Even, when operating in EV mode, emission levels were significantly higher than official estimates. That happened because electric motors were not strong sufficient to operate alone, resulting to combustion motors burning gasoline for almost a third of the distance covered in EV mode.

Regulatory and Financial Implications

Based on calculations, the lowballing of PHEV emissions allowed several major automaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs could pay about €500 more annually in running expenses than would be assumed under lab tests.

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously far from the truth,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and cutting money. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have recently been brought back into policy discussions as automakers have lobbied the EU to relax CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the car sector and resistance from member states with significant automotive industries.

Some senior officials have suggested PHEVs as a possible “flexibility” option to include in the regulation.

An external energy policy expert, who was not involved with the research, described the analysis a “highly valuable addition” after a long period in which segments of the car sector argued there was insufficient information to accurately evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for gasoline or conventional cars,” they stated. “Any policy adjustments concerning PHEVs should be implemented with extreme caution and considering this data.”