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Plug-in hybrid electric vehicles produce almost 5x more planet-heating emissions than lab-reported figures indicate, as per a new analysis.

Widening Discrepancy In Official and Actual Emissions

Data shows that PHEVs release just 19% lower CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy organization. That differs significantly with lab estimates, which suggested a three-quarters decrease in pollution.

Analysts studied information from in-vehicle fuel consumption monitors of 800,000 vehicles sold in Europe between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a senior researcher involved in the report. “That discrepancy is growing and poses a significant problem. Consequently, PHEVs emit nearly as much as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery power compared to total distance. They determined that only a quarter of travel was completed in electric mode, while lab assumptions suggested 84%.

Additionally, when running in EV mode, pollution levels were significantly higher than lab estimates. That happened because EV motors were not strong enough to function alone, leading to combustion motors burning fossil fuels for almost a third of the travel completed in electric mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV CO2 output allowed four large carmaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 more per year in operating expenses than would be assumed under lab tests.

“The strong claims that automakers like to make about their PHEV cars are clearly far from the mark,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Political Discussion and Automotive Lobbying

Plug-in hybrid cars have lately been brought back into policy debates as automakers have pressed the EU to relax CO₂ standards. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the automotive industry and resistance from member states with large car manufacturing.

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

An independent energy policy specialist, who was not involved with the study, described the report a “highly valuable addition” after a long period in which parts of the automotive industry argued there was too little information to properly evaluate actual emissions.

“These findings show, without question, that the difference between official and real-world PHEV energy use and CO₂ emissions is significantly greater than for petrol or conventional vehicles,” the expert said. “Any regulatory adjustments regarding PHEVs should be made with extreme care and considering this evidence.”