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PHEVs emit nearly 5x greater planet-heating pollution than official figures indicate, as per a new analysis.

Widening Gap In Official and Real-World Emissions

Statistics reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel vehicles, according to analysis conducted by a non-profit organization. This contrasts significantly with laboratory estimates, which suggested a 75% reduction in emissions.

Researchers studied information from onboard fuel consumption monitors of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

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

Primary Factors Behind the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the ratio of kilometers travelled in electric mode compared to overall distance. The team determined that just a quarter of travel was completed in EV mode, while official estimates assumed over four-fifths.

Additionally, when operating in electric mode, emission amounts were significantly higher than lab estimates. This happened because EV motors were insufficiently powerful enough to operate alone, leading to engines using gasoline for almost one-third of the distance covered in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled four large carmaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 extra annually in running costs than would be estimated under lab tests.

“The bold claims that automakers often promote about their plug-in hybrid cars are obviously far from the mark,” commented a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy consumption, CO₂ production, and operating costs.”

Political Debate and Industry Pressure

Hybrid cars have lately been brought again into policy debates as carmakers have lobbied the European Union to weaken CO₂ targets. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with significant car manufacturing.

Some high-level officials have proposed plug-in hybrids as a possible “flexibility” solution to include in the regulation.

An external energy policy specialist, who was not involved with the study, described the report a “highly valuable addition” after years in which parts of the car sector argued there was too little information to accurately evaluate actual CO2 output.

“These findings demonstrate, without question, that the gap between lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of that data.”