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Plug-in hybrid cars emit nearly five times greater planet-heating emissions than lab-reported data indicate, as per a recent report.

Growing Gap Between Lab and Actual CO2 Output

Data reveals that PHEVs release just 19% less CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy group. This contrasts sharply with lab tests, which assumed a 75% decrease in emissions.

Researchers studied information from in-vehicle energy use monitors of 800,000 cars registered in the EU from 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are falling,” said a lead researcher participating in the study. “This discrepancy is growing and poses a significant issue. As a result, PHEVs emit nearly as much as petrol cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of miles travelled in electric power compared to total mileage. They found that just a quarter of driving was completed in electric mode, while official estimates assumed over four-fifths.

Additionally, when operating in EV mode, emission levels were significantly higher than lab projections. This happened because EV motors were not strong sufficient to function alone, leading to engines burning fossil fuels for nearly a third of the distance covered in electric mode.

Policy and Economic Consequences

Based on calculations, the lowballing of PHEV emissions allowed four major carmaker companies to escape over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 extra annually in running expenses than is estimated under lab conditions.

“The bold claims that manufacturers like to make about their PHEV cars are obviously way off the mark,” commented a automotive analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running costs.”

Political Debate and Automotive Pressure

Hybrid vehicles have lately been drawn again into political debates as carmakers have pressed the EU to relax CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and opposition from member states with large automotive industries.

Several senior politicians have suggested plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

One external energy policy specialist, who was unaffiliated with the research, called the analysis a “very useful addition” after years in which segments of the automotive sector argued there was too little information to properly assess actual CO2 output.

“These findings show, beyond any doubt, that the gap in official and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel cars,” they said. “Any regulatory changes regarding PHEVs should be implemented with extreme caution and in the light of that evidence.”