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Plug-in hybrid electric vehicles produce almost five times greater planet-heating emissions than lab-reported figures indicate, according to a recent report.

Growing Discrepancy Between Official and Actual Emissions

Data shows that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a non-profit group. That differs sharply with laboratory tests, which suggested a three-quarters reduction in emissions.

Analysts examined data from in-vehicle fuel consumption meters of eight hundred thousand vehicles registered in Europe between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while official figures are falling,” said a senior analyst participating in the study. “That discrepancy is widening and creates a serious issue. As a result, PHEVs emit almost as heavily as petrol cars.”

Primary Reasons Driving the Emissions Gap

Analysts attributed most of the gap to overestimates of the “utility factor” – the percentage of miles travelled in electric power relative to overall mileage. They found that just a quarter of driving was done in EV mode, whereas official assumptions suggested 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than official estimates. This occurred because EV motors were insufficiently powerful sufficient to function independently, resulting to combustion motors burning gasoline for nearly a third of the travel covered in electric mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output allowed several large carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 extra per year in operating expenses than would be estimated under laboratory tests.

“The bold statements that automakers often promote about their plug-in hybrid vehicles are obviously way off the mark,” stated a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and operating expenses.”

Political Debate and Industry Pressure

Hybrid vehicles have recently been brought again into policy debates as carmakers have lobbied the EU to relax CO₂ targets. A proposed prohibition on sales of new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and resistance from EU countries with large automotive manufacturing.

Several high-level officials have suggested PHEVs as a potential “compromise” solution to include in the regulation.

One external energy policy specialist, who was unaffiliated with the study, described the analysis a “very useful addition” after a long period in which parts of the automotive sector argued there was insufficient data to properly evaluate real-world CO2 output.

“The results demonstrate, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional cars,” they said. “Any policy adjustments regarding PHEVs should be implemented with extreme care and considering this evidence.”