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Plug-in hybrid cars produce almost 5x more planet-heating emissions than official figures indicate, according to a recent analysis.

Growing Gap In Official and Real-World CO2 Output

Data reveals that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel vehicles, based on analysis conducted by a advocacy group. That differs sharply with laboratory tests, which assumed a 75% decrease in emissions.

Researchers studied data from onboard energy use monitors of eight hundred thousand vehicles sold in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are falling,” said a senior analyst involved in the study. “This discrepancy is growing and poses a serious issue. As a result, PHEVs emit nearly as much as gasoline cars.”

Key Reasons Driving the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery power compared to overall distance. The team determined that only a quarter of driving was completed in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when running in EV mode, emission levels were significantly higher than lab projections. That occurred because electric motors were insufficiently powerful sufficient to operate alone, resulting to combustion motors burning fossil fuels for nearly a third of the distance covered in electric mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed several large carmaker companies to escape over €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 more per year in operating costs than would be estimated under lab conditions.

“The strong claims that automakers often promote about their PHEV cars are obviously way off the mark,” stated a automotive expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Pressure

Hybrid cars have recently been drawn back into political debates as automakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with significant car manufacturing.

Some high-level politicians have proposed PHEVs as a possible “flexibility” option to introduce in the legislation.

An independent energy economics expert, who was not involved with the research, called the analysis a “very useful addition” after years in which parts of the automotive sector argued there was too little data to properly assess actual CO2 output.

“The results demonstrate, without question, that the gap in official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they said. “Any policy adjustments regarding PHEVs should be implemented with utmost care and considering that data.”