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Plug-in hybrid electric vehicles produce almost 5x more global warming pollution than lab-reported figures indicate, as per a new analysis.

Widening Gap Between Lab and Actual Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel cars, according to analysis carried out by a non-profit group. That differs sharply with lab estimates, which suggested a three-quarters decrease in pollution.

Researchers examined information from in-vehicle fuel consumption meters of 800,000 cars registered in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” stated a lead researcher involved in the report. “This discrepancy is growing and creates a significant issue. As a result, PHEVs pollute almost as much as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in electric power compared to overall mileage. They found that only 27% of travel was done in EV mode, while lab estimates suggested 84%.

Additionally, when running in electric mode, emission amounts were significantly higher than official estimates. This occurred because electric motors were not strong sufficient to operate independently, leading to engines burning gasoline for almost a third of the travel completed in EV mode.

Policy and Economic Consequences

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

Additionally, owners of PHEVs would pay approximately €500 more per year in operating expenses than would be estimated under laboratory conditions.

“The strong claims that manufacturers like to make about their plug-in hybrid cars are clearly far from the truth,” stated a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of energy consumption, CO₂ production, and running costs.”

Political Debate and Industry Lobbying

Hybrid cars have lately been drawn again into political debates as carmakers have pressed the European Union to relax CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant car manufacturing.

Several high-level politicians have suggested PHEVs as a possible “compromise” solution to introduce in the regulation.

An external energy policy expert, who was unaffiliated with the study, called the analysis a “very useful addition” after a long period in which segments of the automotive sector claimed there was too little data to properly evaluate real-world emissions.

“The results show, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they stated. “Any regulatory changes concerning PHEVs should be implemented with extreme caution and in the light of this data.”