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PHEVs release nearly 5x greater global warming pollution than lab-reported figures indicate, according to a new analysis.

Growing Discrepancy In Lab and Real-World CO2 Output

Statistics shows that PHEVs release only 19% lower CO₂ than traditional petrol and diesel vehicles, based on research carried out by a non-profit group. This differs sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use meters of 800,000 vehicles registered in Europe between 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are falling,” said a lead researcher involved in the report. “This gap is widening and creates a serious problem. As a result, PHEVs pollute nearly as much as petrol vehicles.”

Primary Factors Driving the Discrepancy

Researchers linked the majority of the gap to overestimates of the “utility factor” – the percentage of miles travelled in electric mode compared to total mileage. The team found that only 27% of driving was completed in electric mode, whereas official estimates suggested 84%.

Even, when running in EV mode, emission amounts were well above official estimates. That happened because electric motors were not strong enough to function alone, leading to combustion motors burning gasoline for nearly one-third of the travel completed in electric mode.

Regulatory and Financial Implications

Based on calculations, the lowballing of PHEV emissions enabled four large automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could spend about €500 more per year in running expenses than would be assumed under lab tests.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are clearly way off the truth,” stated a automotive expert. “Buyers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have recently been brought back into political debates as carmakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on new combustion engine cars in 2035 has faced intense pressure from the car industry and opposition from EU countries with large automotive industries.

Some high-level politicians have suggested PHEVs as a potential “flexibility” solution to include in the regulation.

One independent energy policy expert, who was unaffiliated with the study, described the analysis a “highly valuable addition” after a long period in which segments of the car sector argued there was too little information to properly evaluate actual CO2 output.

“The results show, beyond any doubt, that the gap in lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or diesel cars,” the expert stated. “Any policy adjustments regarding PHEVs should be implemented with utmost caution and in the light of this evidence.”