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Plug-in hybrid cars produce nearly five times more planet-heating emissions than lab-reported figures show, according to a new report.

Widening Discrepancy Between Lab and Actual CO2 Output

Data shows that PHEVs release just 19% less CO₂ than conventional gas and diesel vehicles, according to analysis carried out by a advocacy organization. That contrasts significantly with laboratory estimates, which assumed a 75% decrease in pollution.

Researchers examined data from in-vehicle energy use meters of 800,000 cars sold in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, up from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” said a senior analyst involved in the study. “This gap is widening and creates a significant problem. Consequently, PHEVs emit almost as much as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers travelled in battery power relative to total distance. They determined that just a quarter of travel was completed in electric mode, while official estimates suggested over four-fifths.

Additionally, when operating in EV mode, pollution amounts were significantly higher than lab projections. This occurred because electric motors were insufficiently powerful sufficient to function alone, resulting to combustion motors using gasoline for almost one-third of the distance covered in EV mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV emissions enabled four major carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by falsely easing compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra annually in operating costs than is estimated under lab conditions.

“The bold statements that automakers like to make about their PHEV cars are clearly far from the mark,” commented a transport expert. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Debate and Automotive Pressure

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

Several senior politicians have suggested PHEVs as a potential “compromise” solution to introduce in the legislation.

One independent energy economics expert, who was not involved with the study, called the analysis a “very useful addition” after a long period in which segments of the car industry argued there was too little information to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with extreme care and in the light of this evidence.”