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Plug-in hybrid electric vehicles release almost five times more planet-heating pollution than lab-reported data show, as per a recent analysis.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics shows that PHEVs release just 19% less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a non-profit organization. That contrasts sharply with lab estimates, which suggested a 75% reduction in emissions.

Researchers examined information from onboard energy use meters of 800,000 vehicles sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, 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 report. “That discrepancy is growing and poses a serious problem. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to overall mileage. They found that only 27% of travel was completed in EV mode, whereas lab estimates assumed 84%.

Even, when operating in electric mode, emission amounts were significantly higher than official estimates. That occurred because EV motors were not strong sufficient to function independently, leading to engines using gasoline for almost one-third of the distance completed in EV mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV emissions enabled four large automaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 extra per year in running costs than would be estimated under laboratory tests.

“The strong claims that automakers often promote about their PHEV vehicles are obviously way off the mark,” commented a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are helping the environment and saving money. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have lately been drawn again into policy discussions as carmakers have pressed the European Union 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 resistance from member states with significant automotive manufacturing.

Several high-level officials have proposed PHEVs as a potential “flexibility” solution to include in the regulation.

An external energy policy expert, who was not involved with the study, called the analysis a “highly valuable contribution” after years in which segments of the automotive industry argued there was too little data to properly evaluate real-world CO2 output.

“These findings demonstrate, without question, that the difference between official and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with utmost caution and considering that evidence.”