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Plug-in hybrid electric vehicles produce almost five times more planet-heating pollution than official data indicate, as per a new report.

Growing Gap Between Lab and Actual Emissions

Data shows that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel cars, based on research conducted by a non-profit organization. That contrasts sharply with laboratory tests, which suggested a 75% reduction in pollution.

Analysts studied information from onboard energy use monitors of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” stated a lead researcher participating in the study. “That gap is growing and poses a significant problem. As a result, PHEVs emit nearly as much as gasoline cars.”

Primary Factors Behind the Discrepancy

Analysts attributed most of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to total distance. The team found that only a quarter of driving was done in electric mode, whereas lab assumptions assumed 84%.

Additionally, when running in electric mode, emission levels were well above lab projections. That occurred because electric motors were insufficiently powerful enough to operate independently, resulting to engines burning fossil fuels for almost one-third of the distance covered in electric mode.

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled several large automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay about €500 more per year in operating costs than is assumed under lab tests.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are clearly way off the truth,” commented a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have lately been drawn again into political debates as automakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car industry and opposition from member states with large automotive industries.

Some high-level officials have suggested PHEVs as a potential “compromise” option to introduce in the legislation.

One independent energy policy expert, who was not involved with the study, called the analysis a “highly valuable contribution” after a long period in which parts of the car industry argued there was too little information to properly evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or diesel cars,” the expert stated. “All policy adjustments concerning PHEVs should be made with extreme care and considering this data.”