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PHEVs emit almost 5x more global warming pollution than lab-reported data show, according to a recent report.

Growing Discrepancy Between Official and Actual CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel cars, based on research carried out by a non-profit organization. That differs sharply with laboratory tests, which suggested a three-quarters decrease in pollution.

Analysts examined data from in-vehicle energy use monitors of 800,000 cars sold 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 estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” said a lead analyst involved in the report. “That gap is widening and poses a significant problem. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Primary Reasons Driving the Emissions Gap

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power compared to overall mileage. They found that just a quarter of driving was completed in EV mode, while lab assumptions suggested over four-fifths.

Even, when running in EV mode, pollution amounts were well above official projections. That happened because electric motors were not strong sufficient to operate alone, leading to engines burning fossil fuels for almost one-third of the distance completed in electric mode.

Regulatory and Economic Consequences

According to calculations, the underestimation of PHEV emissions allowed four major automaker groups to escape over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 extra per year in running expenses than is estimated under laboratory tests.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a automotive expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have lately been drawn back into policy discussions as automakers have lobbied the European Union to weaken CO₂ targets. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and opposition from EU countries with large automotive manufacturing.

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

One independent energy economics expert, who was unaffiliated with the research, called the report a “very useful addition” after years in which segments of the automotive industry argued there was too little data to properly evaluate real-world emissions.

“These findings show, without question, that the difference between lab and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel cars,” they stated. “All regulatory adjustments concerning PHEVs should be implemented with utmost care and considering that evidence.”