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Plug-in hybrid electric vehicles produce almost 5x more global warming pollution than official figures indicate, according to a new analysis.

Growing Gap Between Official and Real-World Emissions

Statistics reveals that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel cars, according to analysis carried out by a non-profit organization. That differs sharply with lab tests, which suggested a 75% decrease in emissions.

Analysts examined data from onboard energy use monitors of 800,000 vehicles registered in Europe from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” stated a lead researcher involved in the report. “This discrepancy is widening and creates a serious issue. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Behind the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power relative to total distance. They determined that only a quarter of travel was done in electric mode, whereas lab estimates assumed 84%.

Even, when running in electric mode, emission amounts were well above lab estimates. This occurred because EV motors were insufficiently powerful sufficient to operate alone, leading to combustion motors using gasoline for almost one-third of the travel completed in EV mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV CO2 output allowed four large carmaker groups to avoid over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 more per year in running costs than is assumed under lab tests.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are obviously far from the truth,” commented a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly improved than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ production, and operating costs.”

Political Debate and Automotive Lobbying

Hybrid vehicles have recently been brought back into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and resistance from EU countries with significant car industries.

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

One independent energy economics specialist, who was not involved with the study, called the report a “very useful contribution” after years in which parts of the car industry claimed there was too little data to accurately assess real-world CO2 output.

“These findings demonstrate, without question, that the difference in official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” the expert stated. “All policy changes regarding PHEVs should be made with extreme care and considering that evidence.”