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Plug-in hybrid electric vehicles release almost five times more global warming pollution than lab-reported figures show, according to a recent report.

Growing Discrepancy Between Official and Actual Emissions

Data shows that PHEVs release just 19% less CO₂ than traditional gas and diesel cars, according to research carried out by a advocacy group. That contrasts significantly with lab tests, which suggested a three-quarters reduction in pollution.

Researchers studied information from in-vehicle energy use monitors of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” stated a senior analyst involved in the report. “That gap is growing and creates a serious problem. As a result, PHEVs pollute almost as much as gasoline cars.”

Key Reasons Driving the Emissions Gap

Researchers linked most of the gap to inflated estimates of the “utility factor” – the ratio of miles travelled in electric power relative to overall mileage. The team found that only a quarter of travel was completed in EV mode, whereas lab estimates assumed 84%.

Even, when running in electric mode, pollution levels were well above lab projections. That happened because electric motors were not strong enough to operate independently, leading to combustion motors burning gasoline for nearly a third of the travel covered in EV mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV emissions allowed several major automaker groups to escape over €5bn in fines between 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend approximately €500 more per year in running costs than would be assumed under lab conditions.

“The strong claims that automakers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and saving costs. In reality, PHEVs are little improved than standard gas and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been brought back into policy debates as automakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on new combustion engine vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with large automotive industries.

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

One independent energy economics expert, who was unaffiliated with the study, called the report a “highly valuable addition” after a long period in which segments of the automotive industry claimed there was too little information to properly evaluate real-world CO2 output.

“The results show, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ output is significantly larger than for petrol or conventional vehicles,” they said. “Any policy changes regarding PHEVs should be made with utmost care and in the light of this data.”