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Plug-in hybrid cars produce almost 5x more planet-heating emissions than lab-reported figures show, as per a new report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release only 19% less CO₂ than conventional petrol and diesel cars, according to research carried out by a advocacy group. That differs significantly with laboratory estimates, which assumed a 75% reduction in pollution.

Researchers studied data from onboard fuel consumption meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” said a senior researcher participating in the report. “That discrepancy is widening and creates a serious problem. As a result, PHEVs pollute nearly as much as gasoline cars.”

Key Reasons Behind the Emissions Gap

Researchers linked the majority of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric power relative to overall distance. The team determined that only 27% of driving was done in electric mode, while lab assumptions suggested over four-fifths.

Even, when running in EV mode, pollution levels were significantly higher than official projections. This happened because electric motors were not strong sufficient to operate independently, leading to combustion motors burning fossil fuels for nearly a third of the travel covered in electric mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV CO2 output enabled several major carmaker groups to avoid over €5bn in penalties between 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

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

“The bold claims that manufacturers like to make about their PHEV cars are clearly far from the truth,” commented a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little improved than regular gas and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought back into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with significant automotive industries.

Several high-level politicians have suggested plug-in hybrids as a possible “compromise” option to include in the regulation.

An external energy economics expert, who was not involved with the study, described the analysis a “very useful contribution” after years in which segments of the car industry argued there was too little information to properly evaluate actual emissions.

“These findings show, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel cars,” the expert said. “All policy adjustments regarding PHEVs should be made with extreme caution and considering this evidence.”