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Plug-in hybrid cars release nearly 5x more global warming emissions than official data show, as per a new report.

Widening Gap Between Lab and Real-World CO2 Output

Data shows that PHEVs release just 19% less CO₂ than conventional gas and diesel vehicles, based on analysis carried out by a advocacy organization. This differs sharply with laboratory estimates, which assumed a three-quarters decrease in pollution.

Analysts examined information from onboard energy use meters of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab estimates, up from three and a half times in 2021.

“Actual emissions are rising, while official figures are falling,” stated a senior researcher involved in the report. “This gap is growing and poses a significant issue. Consequently, PHEVs emit almost as heavily as gasoline vehicles.”

Primary Factors Behind the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric power relative to total mileage. They determined that only a quarter of travel was done in electric mode, while official estimates assumed over four-fifths.

Additionally, when running in electric mode, emission levels were well above official estimates. This happened because EV motors were not strong sufficient to function alone, leading to engines using fossil fuels for almost a third of the distance completed in EV mode.

Policy and Financial Implications

Based on calculations, the underestimation of PHEV CO2 output allowed four major carmaker companies to escape over €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs would pay about €500 extra per year in running costs than would be estimated under laboratory tests.

“The strong statements that automakers often promote about their plug-in hybrid cars are obviously far from the truth,” stated a transport analyst. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are little better than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Policy Debate and Industry Lobbying

Hybrid vehicles have lately been drawn again into political debates as automakers have pressed the EU to relax CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced intense pressure from the car industry and resistance from EU countries with large car manufacturing.

Some high-level officials have proposed plug-in hybrids as a potential “compromise” solution to introduce in the legislation.

One external energy economics expert, who was unaffiliated with the research, called the analysis a “very useful addition” after years in which segments of the car sector claimed there was too little information to accurately evaluate actual CO2 output.

“These findings show, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional vehicles,” they said. “Any policy adjustments concerning PHEVs should be made with extreme caution and considering this evidence.”