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Plug-in hybrid cars produce nearly 5x more global warming emissions than official figures indicate, according to a new report.

Growing Discrepancy Between Official and Real-World CO2 Output

Data reveals that PHEVs emit just 19% less CO₂ than traditional gas and diesel vehicles, according to research conducted by a non-profit organization. This differs significantly with lab tests, which suggested a three-quarters reduction in pollution.

Researchers examined information from onboard fuel consumption meters of 800,000 cars registered in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” stated a senior analyst involved in the study. “That discrepancy is growing and poses a significant problem. Consequently, PHEVs pollute almost as much as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles travelled in electric power compared to total mileage. They determined that only 27% of driving was completed in EV mode, while official assumptions suggested over four-fifths.

Even, when running in electric mode, pollution amounts were significantly higher than official estimates. That occurred because EV motors were not strong sufficient to operate alone, leading to combustion motors using fossil fuels for almost one-third of the travel completed in EV mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV CO2 output allowed several major automaker groups to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 more per year in running costs than is assumed under lab conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are obviously far from the mark,” stated a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have lately been drawn back into policy debates as automakers have lobbied the European Union to weaken CO₂ targets. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with large car industries.

Some senior politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the legislation.

One independent energy policy specialist, who was not involved with the research, described the report a “very useful addition” after a long period in which segments of the automotive industry argued there was insufficient information to accurately evaluate real-world CO2 output.

“The results show, without question, that the gap in official and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or diesel vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with extreme care and in the light of this data.”