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Plug-in hybrid cars emit nearly 5x more planet-heating pollution than official figures indicate, according to a recent analysis.

Growing Gap Between Lab and Real-World Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than conventional gas and diesel cars, based on research carried out by a advocacy organization. That contrasts sharply with lab tests, which assumed a three-quarters reduction in emissions.

Researchers studied information from in-vehicle energy use meters of 800,000 vehicles registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are decreasing,” stated a senior researcher involved in the study. “This discrepancy is growing and creates a serious issue. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles driven in electric mode compared to total distance. They determined that just 27% of driving was done in EV mode, while official assumptions suggested 84%.

Even, when operating in electric mode, emission levels were significantly higher than lab projections. This happened because electric motors were not strong sufficient to function alone, leading to combustion motors burning gasoline for almost a third of the distance completed in electric mode.

Regulatory and Economic Consequences

According to calculations, the lowballing of PHEV CO2 output enabled four major automaker groups to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would pay about €500 extra annually in running expenses than would be estimated under lab conditions.

“The bold statements that automakers like to make about their PHEV cars are obviously way off the truth,” commented a automotive analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little improved than regular petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Pressure

Hybrid vehicles have lately been drawn back into political discussions as automakers have lobbied the EU to weaken CO₂ standards. A planned ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with large car manufacturing.

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

An independent energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable addition” after years in which segments of the automotive industry argued there was too little information to properly assess real-world CO2 output.

“These findings show, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” they stated. “All policy changes regarding PHEVs should be implemented with utmost care and in the light of this data.”