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Plug-in hybrid electric vehicles release nearly 5x more planet-heating pollution than lab-reported data indicate, according to a recent report.

Growing Gap Between Lab and Actual CO2 Output

Data shows that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel vehicles, according to research conducted by a advocacy group. This contrasts significantly with lab tests, which suggested a three-quarters reduction in pollution.

Researchers examined information from in-vehicle fuel consumption meters of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” stated a lead researcher involved in the study. “That discrepancy is widening and poses a significant problem. Consequently, PHEVs pollute almost as heavily as petrol cars.”

Primary Factors Behind the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric power compared to overall mileage. The team found that just 27% of travel was completed in electric mode, while official estimates suggested over four-fifths.

Even, when operating in EV mode, emission levels were well above lab projections. That occurred because electric motors were not strong sufficient to function alone, leading to engines burning fossil fuels for almost a third of the travel completed in electric mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several major automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 more per year in operating expenses than is assumed under lab tests.

“The strong claims that manufacturers like to make about their PHEV cars are obviously far from the mark,” commented a automotive analyst. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have recently been brought again into political discussions as automakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with large automotive industries.

Some senior politicians have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

One independent energy policy expert, who was unaffiliated with the study, described the report a “very useful addition” after years in which parts of the automotive sector claimed there was too little data to properly assess actual CO2 output.

“The results demonstrate, without question, that the gap between lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or conventional vehicles,” they stated. “All policy adjustments concerning PHEVs should be made with extreme caution and in the light of that evidence.”