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PHEVs produce almost 5x more planet-heating pollution than official data indicate, according to a new analysis.

Widening Discrepancy In Lab and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel cars, according to analysis conducted by a advocacy organization. This contrasts sharply with laboratory estimates, which suggested a three-quarters decrease in pollution.

Researchers examined data from onboard energy use meters of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are falling,” said a senior researcher participating in the report. “This gap is widening and creates a serious issue. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Researchers attributed most of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in battery power compared to total mileage. The team determined that just a quarter of travel was done in EV mode, whereas lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, pollution levels were significantly higher than official estimates. That occurred because EV motors were not strong sufficient to function alone, leading to engines using fossil fuels for almost one-third of the travel covered in electric mode.

Regulatory and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output enabled four large carmaker groups to avoid more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 extra annually in operating costs than is assumed under lab tests.

“The bold claims that automakers like to make about their PHEV vehicles are clearly far from the mark,” stated a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy use, CO₂ production, and running costs.”

Political Debate and Industry Pressure

Hybrid cars have recently been brought back into political discussions as automakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and resistance from member states with significant car industries.

Some senior officials have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

One external energy policy specialist, who was not involved with the research, described the report a “very useful addition” after years in which segments of the automotive industry argued there was insufficient data to properly assess real-world CO2 output.

“The results show, without question, that the gap in official and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” the expert said. “All regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of this evidence.”