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Plug-in hybrid cars emit almost 5x greater planet-heating emissions than official figures indicate, according to a new analysis.

Widening Discrepancy Between Official and Actual Emissions

Statistics reveals that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel cars, according to research conducted by a advocacy group. This differs sharply with lab estimates, which suggested a three-quarters decrease in emissions.

Researchers studied information from onboard energy use monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” stated a senior analyst involved in the report. “This gap is growing and poses a significant issue. Consequently, PHEVs emit almost as heavily as petrol cars.”

Key Reasons Driving the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric mode relative to overall distance. The team found that only a quarter of driving was done in electric mode, while official assumptions assumed over four-fifths.

Additionally, when operating in electric mode, pollution levels were well above official estimates. That occurred because EV motors were insufficiently powerful sufficient to operate alone, leading to engines using gasoline for almost one-third of the distance completed in EV mode.

Policy and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several large automaker groups to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 extra per year in operating costs than would be assumed under lab conditions.

“The bold claims that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” stated a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are little better than regular petrol and diesel vehicles in terms of energy use, CO₂ production, and operating expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought back into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the car industry and opposition from member states with large car manufacturing.

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

An independent energy economics specialist, who was unaffiliated with the study, called the report a “highly valuable contribution” after years in which segments of the car industry argued there was insufficient data to properly assess actual CO2 output.

“These findings show, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel cars,” the expert said. “All policy adjustments concerning PHEVs should be implemented with extreme care and in the light of this data.”