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Plug-in hybrid cars release almost 5x more global warming pollution than lab-reported figures indicate, according to a recent analysis.

Growing Discrepancy In Official and Real-World CO2 Output

Statistics shows that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a non-profit organization. That differs sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Analysts examined data from in-vehicle fuel consumption meters of 800,000 cars sold in Europe between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” stated a senior analyst involved in the report. “That discrepancy is widening and poses a serious issue. As a result, PHEVs pollute nearly as much as petrol cars.”

Key Factors Driving the Emissions Gap

Researchers attributed the majority of the gap to overestimates of the “electric driving share” – the percentage of miles travelled in electric power relative to total distance. The team found that only a quarter of travel was completed in electric mode, while official estimates assumed over four-fifths.

Even, when running in electric mode, emission levels were well above lab estimates. That happened because electric motors were not strong sufficient to function independently, resulting to combustion motors using fossil fuels for nearly one-third of the travel completed in electric mode.

Policy and Financial Implications

Based on calculations, the underestimation of PHEV CO2 output enabled four major automaker companies to escape over €5bn in penalties between 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs could pay approximately €500 more per year in operating expenses than is estimated under lab tests.

“The strong statements that manufacturers often promote about their PHEV vehicles are obviously way off the mark,” commented a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little improved than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have recently been drawn back into political discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and opposition from EU countries with significant car manufacturing.

Some senior officials have suggested PHEVs as a potential “flexibility” solution to include in the regulation.

One external energy policy expert, who was not involved with the study, described the analysis a “highly valuable addition” after years in which parts of the car sector claimed there was too little information to properly evaluate actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional cars,” they said. “All policy changes concerning PHEVs should be made with extreme care and considering this evidence.”