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Plug-in hybrid cars produce nearly five times greater planet-heating emissions than lab-reported figures show, according to a recent analysis.

Growing Gap In Official and Real-World Emissions

Data reveals that PHEVs release only 19% lower CO₂ than traditional gas and diesel cars, according to research conducted by a advocacy group. That differs significantly with laboratory estimates, which assumed a 75% decrease in pollution.

Researchers examined data from in-vehicle fuel consumption meters of eight hundred thousand cars sold in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are decreasing,” said a lead researcher participating in the report. “That discrepancy is widening and poses a significant issue. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Behind the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in battery power relative to total mileage. They found that just 27% of driving was completed in electric mode, while lab estimates suggested 84%.

Additionally, when running in EV mode, emission amounts were well above lab estimates. That occurred because EV motors were not strong enough to operate independently, leading to engines burning gasoline for nearly a third of the distance completed in electric mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV CO2 output enabled several major carmaker companies to escape over €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay approximately €500 more annually in running costs than is assumed under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are clearly way off the mark,” stated a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than standard petrol and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Political Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn back into policy debates as automakers have pressed the European Union to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car industry and opposition from EU countries with significant automotive manufacturing.

Several senior officials have suggested plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

An independent energy policy expert, who was unaffiliated with the research, called the report a “very useful addition” after a long period in which parts of the car industry argued there was too little data to properly assess real-world CO2 output.

“These findings show, beyond any doubt, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel vehicles,” they stated. “All regulatory changes regarding PHEVs should be implemented with extreme care and considering that data.”