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Plug-in hybrid electric vehicles emit almost five times more global warming emissions than lab-reported data show, as per a new analysis.

Growing Discrepancy Between Official and Real-World Emissions

Statistics reveals that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel cars, based on analysis carried out by a advocacy organization. This contrasts significantly with lab tests, which suggested a three-quarters reduction in emissions.

Researchers examined information from onboard energy use meters of eight hundred thousand vehicles sold in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” said a lead researcher participating in the report. “This gap is widening and creates a significant problem. Consequently, PHEVs pollute nearly as much as petrol cars.”

Key Factors Behind the Discrepancy

Researchers attributed most of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in battery power relative to total mileage. They determined that just a quarter of travel was completed in electric mode, whereas lab assumptions suggested 84%.

Even, when operating in electric mode, pollution levels were significantly higher than official projections. This occurred because electric motors were not strong sufficient to function independently, resulting to combustion motors burning fossil fuels for almost one-third of the distance covered in electric mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV emissions enabled four major carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 more per year in operating expenses than is estimated under laboratory tests.

“The bold statements that manufacturers often promote about their PHEV vehicles are obviously far from the truth,” stated a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Debate and Industry Lobbying

Hybrid vehicles have recently been drawn back into political debates as carmakers have lobbied the European Union to weaken CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with large automotive manufacturing.

Some senior officials have proposed PHEVs as a potential “compromise” option to introduce in the regulation.

An external energy policy specialist, who was not involved with the study, described the report a “highly valuable contribution” after years in which parts of the car industry claimed there was too little information to accurately evaluate real-world CO2 output.

“The results show, beyond any doubt, that the gap between lab and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or diesel cars,” they said. “All regulatory changes concerning PHEVs should be made with extreme caution and considering this evidence.”