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PHEVs emit almost 5x greater planet-heating pollution than lab-reported data indicate, according to a new analysis.

Growing Gap Between Official and Real-World CO2 Output

Statistics reveals that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, according to research carried out by a advocacy organization. That differs sharply with lab estimates, which assumed a three-quarters reduction in emissions.

Analysts examined information from in-vehicle fuel consumption monitors of 800,000 vehicles sold in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are falling,” said a lead analyst involved in the report. “That gap is widening and poses a significant issue. Consequently, PHEVs emit nearly as much as gasoline cars.”

Key Factors Behind the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric mode compared to overall mileage. They found that just a quarter of driving was done in electric mode, while official assumptions suggested over four-fifths.

Additionally, when running in EV mode, emission amounts were significantly higher than lab projections. This happened because EV motors were not strong enough to function independently, resulting to combustion motors using fossil fuels for almost a third of the distance completed in EV mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed several major automaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could pay about €500 extra per year in operating expenses than would be estimated under laboratory conditions.

“The strong claims that automakers like to make about their plug-in hybrid cars are clearly far from the truth,” stated a automotive expert. “Buyers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Political Discussion and Automotive Lobbying

Hybrid cars have recently been brought back into policy debates as carmakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the car sector and resistance from EU countries with significant car manufacturing.

Some high-level officials have suggested PHEVs as a possible “flexibility” solution to introduce in the regulation.

One external energy policy specialist, who was unaffiliated with the study, called the report a “highly valuable contribution” after a long period in which segments of the car sector claimed there was too little information to accurately assess actual emissions.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” they said. “Any regulatory adjustments regarding PHEVs should be implemented with utmost care and in the light of that evidence.”