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Plug-in hybrid cars produce almost 5x more planet-heating pollution than official data show, according to a new report.

Growing Discrepancy In Lab and Real-World Emissions

Data shows that PHEVs release just one-fifth less CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a advocacy group. That contrasts sharply with laboratory tests, which assumed a three-quarters reduction in pollution.

Analysts studied data from onboard fuel consumption monitors of 800,000 vehicles sold in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are falling,” stated a senior analyst involved in the report. “This discrepancy is growing and creates a significant issue. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Key Factors Behind the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in electric power relative to overall distance. The team found that just a quarter of travel was done in electric mode, whereas official assumptions suggested over four-fifths.

Additionally, when operating in electric mode, pollution levels were significantly higher than official projections. That happened because electric motors were not strong enough to function independently, leading to combustion motors burning gasoline for almost a third of the travel completed in EV mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV emissions enabled four major automaker groups to avoid more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 more annually in operating expenses than is assumed under laboratory conditions.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are obviously far from the truth,” stated a automotive analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have lately been brought again into political discussions as automakers have pressed the European Union to relax CO₂ targets. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the car sector and resistance from EU countries with large car industries.

Some senior officials have proposed PHEVs as a potential “flexibility” option to introduce in the regulation.

One independent energy economics expert, who was unaffiliated with the research, described the analysis a “very useful addition” after years in which segments of the car industry argued there was insufficient data to properly assess actual CO2 output.

“The results show, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or conventional vehicles,” they said. “Any policy adjustments regarding PHEVs should be implemented with extreme care and considering that data.”