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Plug-in hybrid electric vehicles produce almost five times greater global warming pollution than official figures indicate, as per a new analysis.

Widening Discrepancy In Official and Actual Emissions

Data shows that PHEVs release just 19% less CO₂ than conventional gas and diesel cars, based on analysis carried out by a advocacy group. That contrasts significantly with lab tests, which assumed a three-quarters reduction in pollution.

Analysts studied information from in-vehicle fuel consumption meters of eight hundred thousand cars registered in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are falling,” said a lead analyst participating in the report. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Reasons Behind the Emissions Gap

Analysts linked most of the gap to overestimates of the “utility factor” – the ratio of miles travelled in electric mode compared to total mileage. The team determined that only 27% of driving was done in electric mode, whereas official estimates suggested over four-fifths.

Additionally, when operating in electric mode, emission levels were well above official projections. This happened because electric motors were insufficiently powerful enough to operate alone, resulting to engines using fossil fuels for almost a third of the travel covered in electric mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV emissions enabled several major carmaker companies to avoid over €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 more annually in running costs than is estimated under laboratory conditions.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have lately been drawn again into policy discussions as carmakers have lobbied the European Union to relax CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with significant car industries.

Some senior politicians have suggested PHEVs as a possible “compromise” option to include in the regulation.

One independent energy economics expert, who was not involved with the research, described the analysis a “highly valuable contribution” after years in which segments of the car industry argued there was too little data to accurately evaluate actual emissions.

“These findings show, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or conventional cars,” the expert said. “All regulatory changes regarding PHEVs should be made with utmost care and considering that data.”