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Plug-in hybrid cars release nearly 5x more global warming emissions than lab-reported figures show, according to a new analysis.

Growing Gap In Official and Real-World CO2 Output

Data reveals that PHEVs emit only 19% lower CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a non-profit group. This contrasts sharply with laboratory estimates, which suggested a three-quarters decrease in pollution.

Analysts examined data from in-vehicle fuel consumption monitors of eight hundred thousand vehicles sold in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” said a senior researcher participating in the report. “This discrepancy is widening and poses a significant issue. As a result, PHEVs emit nearly as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery power compared to total mileage. The team determined that just a quarter of driving was completed in electric mode, while lab estimates suggested over four-fifths.

Additionally, when running in EV mode, pollution levels were significantly higher than lab estimates. This occurred because electric motors were insufficiently powerful enough to operate independently, leading to combustion motors burning gasoline for nearly a third of the distance covered in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed four major automaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 more annually in running expenses than is assumed under lab conditions.

“The bold statements that automakers like to make about their PHEV vehicles are obviously way off the mark,” commented 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 little improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Political Discussion and Automotive Lobbying

Hybrid cars have lately been brought again into policy debates as automakers have pressed the EU to relax CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the car sector and opposition from EU countries with large car manufacturing.

Some high-level politicians have proposed plug-in hybrids as a possible “flexibility” option to include in the regulation.

An independent energy policy expert, who was unaffiliated with the research, described the report a “highly valuable addition” after a long period in which segments of the car sector argued there was insufficient data to properly evaluate real-world CO2 output.

“The results show, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or diesel vehicles,” the expert said. “All policy changes regarding PHEVs should be made with extreme care and in the light of this data.”