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Plug-in hybrid electric vehicles release almost five times greater global warming pollution than lab-reported figures indicate, as per a new report.

Widening Gap In Official and Real-World CO2 Output

Statistics shows that PHEVs emit just one-fifth less CO₂ than traditional petrol and diesel cars, based on analysis conducted by a advocacy group. This contrasts sharply with lab estimates, which assumed a three-quarters decrease in pollution.

Researchers examined data from onboard energy use monitors of 800,000 vehicles sold in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” stated a lead researcher participating in the study. “This gap is growing and poses a serious issue. As a result, PHEVs emit nearly as much as petrol cars.”

Key Factors Driving the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery power relative to overall mileage. The team determined that only a quarter of travel was completed in electric mode, while official estimates assumed 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab projections. That happened because EV motors were insufficiently powerful enough to operate alone, leading to combustion motors burning gasoline for almost a third of the distance completed in EV mode.

Policy and Financial Implications

According to calculations, the underestimation of PHEV emissions enabled four large carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would pay about €500 more annually in running expenses than would be estimated under laboratory tests.

“The bold claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” stated a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought again into policy debates as automakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with significant car manufacturing.

Some high-level officials have proposed PHEVs as a potential “flexibility” option to introduce in the legislation.

An independent energy economics expert, who was unaffiliated with the study, described the analysis a “highly valuable addition” after years in which segments of the car industry argued there was insufficient data to accurately evaluate real-world emissions.

“These findings demonstrate, without question, that the gap between lab and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional vehicles,” the expert stated. “All regulatory adjustments concerning PHEVs should be made with utmost care and considering that evidence.”