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Plug-in hybrid electric vehicles release almost 5x greater global warming pollution than official data show, as per a new report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics reveals that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a non-profit group. This differs sharply with lab estimates, which assumed a 75% reduction in emissions.

Researchers examined data from in-vehicle energy use monitors of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are falling,” stated a lead analyst involved in the report. “This gap is growing and creates a significant problem. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers linked the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in electric mode relative to overall distance. They determined that just a quarter of travel was completed in electric mode, while lab assumptions assumed 84%.

Even, when running in electric mode, emission amounts were significantly higher than official projections. This happened because EV motors were not strong sufficient to function independently, resulting to combustion motors using gasoline for nearly one-third of the travel completed in EV mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed several large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra annually in operating expenses than would be assumed under laboratory tests.

“The strong statements that manufacturers like to make about their PHEV cars are obviously far from the mark,” stated a automotive expert. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Hybrid vehicles have recently been brought again into policy discussions as carmakers have pressed the European Union to relax CO₂ standards. A planned ban on sales of new internal combustion cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large car manufacturing.

Some senior politicians have suggested plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

One independent energy policy expert, who was not involved with the research, described the analysis a “very useful addition” after a long period in which parts of the automotive industry argued there was insufficient information to properly evaluate real-world emissions.

“The results demonstrate, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” the expert stated. “Any policy changes regarding PHEVs should be implemented with extreme care and considering that data.”