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Plug-in hybrid electric vehicles release almost 5x greater global warming pollution than lab-reported figures indicate, as per a new analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Statistics shows that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, based on analysis conducted by a non-profit organization. This contrasts sharply with laboratory tests, which assumed a 75% reduction in pollution.

Analysts studied information from in-vehicle energy use meters of 800,000 vehicles registered in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are rising, while official emissions are decreasing,” said a lead researcher involved in the study. “That gap is growing and creates a serious problem. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Primary Factors Driving the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers travelled in battery mode relative to total mileage. They found that just 27% of travel was completed in electric mode, whereas official assumptions suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab projections. That happened because electric motors were not strong enough to operate alone, leading to combustion motors burning fossil fuels for nearly one-third of the travel covered in EV mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV emissions allowed four large automaker companies to avoid over €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 more annually in operating costs than would be assumed under laboratory conditions.

“The bold claims that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are little improved than standard gas and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been brought back into political discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with large car industries.

Several high-level politicians have proposed plug-in hybrids as a potential “compromise” solution to include in the legislation.

One external energy policy specialist, who was unaffiliated with the research, called the analysis a “highly valuable addition” after years in which segments of the automotive sector claimed there was too little data to properly assess real-world CO2 output.

“The results show, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel cars,” the expert stated. “All regulatory adjustments concerning PHEVs should be made with extreme care and in the light of that evidence.”