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Plug-in hybrid electric vehicles produce nearly five times greater planet-heating emissions than official data show, according to a new report.

Widening Gap Between Official and Real-World Emissions

Data reveals that PHEVs emit just 19% lower CO₂ than traditional petrol and diesel vehicles, based on analysis conducted by a advocacy group. That differs sharply with lab tests, which suggested a three-quarters reduction in pollution.

Analysts studied information from in-vehicle energy use meters of 800,000 vehicles sold in Europe between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than official figures, up from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a lead researcher participating in the report. “This discrepancy is widening and creates a significant issue. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Key Reasons Behind the Emissions Gap

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to overall mileage. The team determined that just a quarter of driving was done in electric mode, while official assumptions suggested 84%.

Additionally, when running in electric mode, pollution amounts were significantly higher than official estimates. That happened because electric motors were insufficiently powerful sufficient to function alone, leading to combustion motors using fossil fuels for almost one-third of the distance completed in electric mode.

Regulatory and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output enabled several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs could pay approximately €500 more annually in operating costs than is assumed under lab conditions.

“The bold statements that automakers like to make about their PHEV cars are clearly far from the mark,” commented a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Lobbying

Hybrid cars have recently been brought again into policy debates as automakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and opposition from member states with large automotive manufacturing.

Some senior officials have proposed plug-in hybrids as a possible “compromise” option to introduce in the regulation.

One external energy economics specialist, who was unaffiliated with the study, called the analysis a “very useful addition” after a long period in which parts of the car sector claimed there was insufficient information to properly evaluate real-world emissions.

“These findings demonstrate, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ emissions is much, much larger than for gasoline or conventional cars,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with extreme caution and considering this data.”