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Plug-in hybrid electric vehicles release nearly five times more global warming pollution than official figures show, according to a recent analysis.

Growing Gap Between Official and Actual CO2 Output

Statistics shows that PHEVs release only one-fifth lower CO₂ than conventional gas and diesel cars, according to analysis carried out by a non-profit organization. That contrasts sharply with laboratory tests, which assumed a three-quarters decrease in emissions.

Researchers examined data from onboard energy use meters of eight hundred thousand vehicles sold in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” said a lead analyst involved in the study. “This discrepancy is growing and creates a serious problem. As a result, PHEVs pollute almost as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of miles driven in battery mode relative to total mileage. They determined that only a quarter of travel was done in electric mode, while lab estimates suggested 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab estimates. That occurred because electric motors were insufficiently powerful sufficient to operate alone, leading to engines using fossil fuels for nearly a third of the distance covered in electric mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV emissions allowed several large automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 extra per year in running expenses than is assumed under lab conditions.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are clearly way off the truth,” commented a transport expert. “Buyers are being duped into believing that by buying a PHEV, they are helping the environment and saving costs. In reality, PHEVs are little better than regular gas and diesel cars in terms of energy use, CO₂ production, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been brought back into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and resistance from EU countries with large car manufacturing.

Some high-level officials have suggested plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

One external energy policy specialist, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the automotive industry claimed there was insufficient data to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional vehicles,” the expert stated. “All regulatory adjustments concerning PHEVs should be implemented with utmost caution and in the light of this data.”