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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating pollution than official figures indicate, according to a new analysis.

Widening Gap Between Lab and Real-World CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a non-profit organization. That contrasts significantly with lab estimates, which suggested a three-quarters reduction in emissions.

Analysts examined information from in-vehicle fuel consumption meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” stated a senior researcher participating in the study. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs pollute nearly as heavily as gasoline cars.”

Key Factors Driving the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in battery power compared to total mileage. They found that just a quarter of driving was done in electric mode, while lab assumptions suggested 84%.

Even, when operating in EV mode, emission amounts were significantly higher than lab projections. That occurred because EV motors were insufficiently powerful sufficient to function alone, leading to combustion motors burning gasoline for almost a third of the distance completed in EV mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV CO2 output enabled several large automaker groups to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend approximately €500 extra per year in operating expenses than is assumed under lab conditions.

“The bold claims that automakers like to make about their PHEV cars are obviously far from the truth,” stated a transport analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little better than standard gas and diesel cars in terms of fuel use, CO₂ production, and operating costs.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been drawn back into political discussions as automakers have lobbied the EU to relax CO₂ targets. A proposed ban on new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and opposition from EU countries with large automotive manufacturing.

Several high-level politicians have suggested PHEVs as a possible “flexibility” solution to include in the regulation.

One independent energy economics specialist, who was unaffiliated with the research, described the report a “very useful addition” after years in which parts of the automotive sector claimed there was too little information to properly evaluate real-world emissions.

“The results show, without question, that the gap in official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” they stated. “Any regulatory adjustments regarding PHEVs should be implemented with extreme care and in the light of that data.”