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Plug-in hybrid electric vehicles emit nearly five times greater global warming emissions than official data indicate, according to a new analysis.

Widening Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit organization. That differs significantly with laboratory estimates, which assumed a three-quarters reduction in pollution.

Researchers studied information from onboard fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are falling,” stated a senior researcher participating in the report. “That gap is growing and creates a serious problem. As a result, PHEVs emit almost as heavily as petrol vehicles.”

Key Factors Behind the Emissions Gap

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the percentage of miles travelled in electric mode relative to overall distance. The team found that only a quarter of travel was completed in electric mode, while official estimates assumed over four-fifths.

Additionally, when running in electric mode, emission amounts were well above lab estimates. This happened because electric motors were insufficiently powerful enough to operate independently, leading to combustion motors using gasoline for nearly a third of the travel completed in EV mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV emissions allowed several major automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by falsely easing adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend approximately €500 more per year in operating costs than would be assumed under laboratory conditions.

“The strong statements that manufacturers like to make about their PHEV vehicles are obviously way off the mark,” stated a automotive expert. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Lobbying

Hybrid cars have lately been drawn back into policy discussions as automakers have pressed the EU to weaken CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with large car industries.

Some senior politicians have proposed plug-in hybrids as a potential “compromise” option to include in the regulation.

An independent energy policy specialist, who was not involved with the study, called the report a “very useful addition” after years in which parts of the automotive industry argued there was too little information to properly assess actual emissions.

“The results demonstrate, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ output is significantly larger than for petrol or conventional vehicles,” they said. “All policy adjustments regarding PHEVs should be implemented with extreme caution and in the light of this evidence.”