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Plug-in hybrid cars emit almost five times greater global warming pollution than lab-reported figures indicate, according to a new analysis.

Widening Discrepancy In Official and Real-World Emissions

Data reveals that PHEVs release only one-fifth less CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy group. This differs significantly with lab estimates, which suggested a three-quarters decrease in pollution.

Researchers studied data from onboard energy use monitors of 800,000 cars sold 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 figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are decreasing,” said a lead analyst involved in the study. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in battery mode compared to total mileage. The team determined that just a quarter of travel was completed in electric mode, whereas official estimates suggested 84%.

Additionally, when running in electric mode, emission levels were well above lab projections. This occurred because EV motors were not strong sufficient to function independently, leading to combustion motors burning gasoline for almost one-third of the distance completed in EV mode.

Regulatory and Financial Consequences

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

Furthermore, owners of PHEVs could pay approximately €500 more annually in operating costs than is assumed under lab tests.

“The bold claims that manufacturers like to make about their PHEV vehicles are obviously far from the truth,” commented a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ production, and running costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been drawn again into political debates as carmakers have pressed the European Union to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the car industry and opposition from member states with significant automotive manufacturing.

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

One independent energy economics expert, who was not involved with the research, called the report a “very useful contribution” after a long period in which segments of the automotive sector argued there was too little data to accurately evaluate actual emissions.

“The results demonstrate, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel cars,” they stated. “Any policy changes regarding PHEVs should be made with extreme caution and considering that evidence.”