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Plug-in hybrid electric vehicles produce almost 5x greater planet-heating pollution than lab-reported data indicate, as per a new analysis.

Growing Gap Between Lab and Actual Emissions

Data shows that PHEVs emit only 19% less CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit organization. That differs significantly with lab estimates, which suggested a three-quarters decrease in pollution.

Analysts studied information from onboard fuel consumption meters of 800,000 cars sold in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” said a senior researcher participating in the report. “That discrepancy is growing and creates a significant issue. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power relative to overall distance. The team determined that just 27% of driving was completed in EV mode, while official estimates assumed 84%.

Additionally, when operating in EV mode, emission levels were significantly higher than official estimates. That happened because EV motors were insufficiently powerful sufficient to operate alone, leading to engines using gasoline for nearly one-third of the distance covered in EV mode.

Policy and Economic Implications

According to calculations, the underestimation of PHEV emissions enabled four large carmaker companies to avoid more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 more per year in operating expenses than is assumed under lab conditions.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the mark,” commented a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little better than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been brought again into political discussions as carmakers have pressed the EU to relax CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and resistance from member states with large car manufacturing.

Some senior politicians have proposed PHEVs as a possible “compromise” option to introduce in the regulation.

An external energy policy specialist, who was unaffiliated with the research, described the analysis a “very useful contribution” after a long period in which parts of the car sector claimed there was insufficient information to properly assess actual emissions.

“These findings demonstrate, without question, that the difference between lab and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or conventional cars,” the expert stated. “All policy adjustments concerning PHEVs should be made with utmost care and considering that evidence.”