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Plug-in hybrid cars emit nearly 5x more planet-heating emissions than official data indicate, according to a new analysis.

Widening Discrepancy In Official and Actual Emissions

Statistics reveals that PHEVs release only 19% lower CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy organization. That differs significantly with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts studied information from in-vehicle energy use meters of 800,000 vehicles registered in the EU from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” stated a lead analyst involved in the study. “That discrepancy is growing and creates a serious issue. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery power compared to overall distance. They found that just a quarter of travel was completed in electric mode, while official assumptions suggested 84%.

Even, when running in electric mode, emission levels were significantly higher than official estimates. This happened because electric motors were not strong sufficient to function alone, resulting to engines using fossil fuels for almost one-third of the distance completed in electric mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV CO2 output allowed several large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 more annually in running costs than would be assumed under laboratory conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are clearly far from the truth,” commented a transport analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Industry Lobbying

Hybrid cars have recently been drawn again into political debates as automakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive sector and resistance from member states with large car industries.

Several senior officials have proposed plug-in hybrids as a potential “compromise” option to include in the regulation.

An external energy policy expert, who was not involved with the study, called the analysis a “very useful contribution” after years in which parts of the automotive sector argued there was too little information to accurately assess real-world CO2 output.

“These findings demonstrate, without question, that the difference between lab and real-world PHEV energy use and CO₂ output is much, much greater than for gasoline or conventional cars,” they said. “All policy adjustments regarding PHEVs should be implemented with extreme care and considering that data.”