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Plug-in hybrid cars produce almost five times more planet-heating pollution than lab-reported data show, as per a new report.

Growing Discrepancy Between Official and Real-World Emissions

Statistics reveals that PHEVs release only 19% less CO₂ than traditional petrol and diesel vehicles, based on research carried out by a advocacy organization. This differs sharply with lab tests, which suggested a 75% reduction in emissions.

Researchers studied data from onboard fuel consumption monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported figures are falling,” said a senior researcher participating in the study. “This gap is growing and poses a significant issue. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Factors Behind the Emissions Gap

Researchers linked the majority of the gap to overestimates of the “utility factor” – the ratio of kilometers travelled in battery power compared to total distance. The team determined that only a quarter of travel was done in electric mode, while official estimates suggested 84%.

Even, when running in electric mode, emission amounts were significantly higher than lab projections. That occurred because EV motors were insufficiently powerful enough to operate alone, leading to combustion motors using fossil fuels for almost one-third of the distance covered in electric mode.

Regulatory and Financial Implications

Based on estimates, the lowballing of PHEV emissions enabled four major carmaker companies to avoid over €5bn in penalties from 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay about €500 more annually in operating costs than is estimated under lab tests.

“The strong statements that automakers often promote about their PHEV cars are obviously far from the mark,” stated a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have lately been drawn back into political discussions as carmakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy pressure from the car sector and resistance from EU countries with significant automotive manufacturing.

Several high-level officials have proposed PHEVs as a potential “compromise” option to include in the legislation.

An external energy economics expert, who was unaffiliated with the study, called the report a “highly valuable addition” after a long period in which parts of the automotive sector argued there was insufficient data to properly evaluate actual emissions.

“These findings demonstrate, without question, that the gap in official and real-world PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel cars,” the expert stated. “All regulatory changes concerning PHEVs should be made with extreme care and in the light of this evidence.”