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PHEVs emit nearly five times greater planet-heating pollution than lab-reported figures show, as per a new analysis.

Widening Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs emit only one-fifth lower CO₂ than traditional gas and diesel vehicles, based on research carried out by a non-profit group. That differs significantly with lab tests, which assumed a 75% reduction in emissions.

Researchers examined data from onboard fuel consumption monitors of 800,000 vehicles registered in Europe from 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are decreasing,” said a senior researcher involved in the study. “This discrepancy is widening and creates a serious issue. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in battery mode compared to total distance. They found that just 27% of driving was done in electric mode, while lab estimates assumed 84%.

Additionally, when running in electric mode, pollution amounts were significantly higher than lab projections. That happened because EV motors were insufficiently powerful enough to operate independently, leading to engines using gasoline for nearly one-third of the distance covered in electric mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV CO2 output enabled several major carmaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 extra per year in running expenses than would be estimated under laboratory conditions.

“The strong statements that automakers often promote about their PHEV vehicles are obviously way off the mark,” commented a automotive expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are little better than standard petrol and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Debate and Automotive Lobbying

Hybrid vehicles have lately been drawn again into political debates as automakers have lobbied the European Union to weaken CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced intense pressure from the car industry and resistance from member states with significant car industries.

Several senior officials have suggested plug-in hybrids as a possible “compromise” option to include in the regulation.

One independent energy policy specialist, who was unaffiliated with the study, called the analysis a “very useful addition” after years in which parts of the automotive sector claimed there was insufficient information to accurately assess real-world CO2 output.

“These findings show, without question, that the gap in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional vehicles,” they said. “Any regulatory changes concerning PHEVs should be made with extreme caution and considering this data.”