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Plug-in hybrid electric vehicles release nearly five times greater planet-heating pollution than lab-reported figures show, according to a new analysis.

Growing Discrepancy In Official and Real-World Emissions

Data reveals that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel cars, based on research conducted by a advocacy group. This differs significantly with laboratory tests, which assumed a three-quarters decrease in emissions.

Analysts studied data from in-vehicle energy use meters of 800,000 vehicles registered in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” stated a lead analyst involved in the study. “This gap is widening and creates a significant issue. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Key Factors Driving the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in electric mode compared to total mileage. They found that only a quarter of travel was done in electric mode, while official assumptions suggested over four-fifths.

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

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV CO2 output allowed four major automaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay approximately €500 more per year in operating expenses than is assumed under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a automotive expert. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are little better than standard gas and diesel cars in terms of energy use, CO₂ production, and running costs.”

Political Debate and Industry Pressure

Hybrid vehicles have lately been brought back into policy discussions as automakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with significant car manufacturing.

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

An independent energy economics specialist, who was unaffiliated with the research, described the analysis a “very useful contribution” after years in which segments of the automotive industry argued there was insufficient information to accurately assess real-world emissions.

“The results demonstrate, beyond any doubt, that the gap in lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel cars,” the expert stated. “Any policy changes regarding PHEVs should be made with utmost caution and in the light of that data.”