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Plug-in hybrid cars release almost five times greater planet-heating emissions than official data indicate, as per a new report.

Growing Gap In Lab and Real-World CO2 Output

Data shows that PHEVs release just one-fifth less CO₂ than traditional gas and diesel vehicles, based on research conducted by a advocacy organization. That differs significantly with laboratory tests, which assumed a 75% decrease in pollution.

Analysts studied information from onboard energy use meters of 800,000 cars registered in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” stated a senior analyst involved in the study. “That gap is widening and creates a significant problem. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in battery mode relative to total distance. They found that only 27% of travel was completed in electric mode, while official estimates suggested 84%.

Additionally, when running in electric mode, pollution amounts were significantly higher than lab estimates. This happened because EV motors were not strong sufficient to operate independently, resulting to engines burning fossil fuels for almost a third of the travel completed in electric mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV emissions allowed four large automaker companies to avoid over €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay approximately €500 extra annually in operating costs than would be assumed under lab conditions.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are obviously way off the truth,” commented a transport expert. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting money. In reality, PHEVs are little improved than regular gas and diesel cars in terms of energy use, CO₂ production, and operating expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been drawn back into political debates as carmakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and resistance from EU countries with significant automotive manufacturing.

Several senior officials have suggested PHEVs as a potential “compromise” solution to introduce in the regulation.

One external energy economics specialist, who was not involved with the study, called the report a “highly valuable addition” after a long period in which parts of the automotive sector claimed there was too little data to properly assess actual emissions.

“The results demonstrate, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel cars,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with utmost care and in the light of this data.”