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Plug-in hybrid cars emit nearly five times more planet-heating pollution than lab-reported data indicate, according to a new report.

Growing Gap In Lab and Actual Emissions

Data reveals that PHEVs release only 19% less CO₂ than conventional gas and diesel vehicles, according to research conducted by a advocacy organization. That contrasts significantly with lab estimates, which suggested a 75% reduction in emissions.

Analysts studied data from onboard energy use monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported figures are falling,” stated a senior analyst involved in the study. “That discrepancy is widening and creates a significant issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Key Factors Behind the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode compared to total mileage. The team found that only a quarter of travel was done in EV mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution levels were well above lab projections. That happened because electric motors were not strong enough to function alone, resulting to combustion motors using gasoline for almost a third of the distance covered in EV mode.

Regulatory and Financial Implications

According to estimates, the underestimation of PHEV CO2 output enabled four major carmaker companies to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ standards.

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

“The bold statements that manufacturers like to make about their PHEV vehicles are obviously far from the truth,” commented a transport analyst. “Buyers are being misled into thinking that by purchasing a PHEV, they are helping the environment and saving costs. Actually, PHEVs are only slightly better than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating costs.”

Political Discussion and Automotive Pressure

Hybrid cars have recently been brought again into political debates as automakers have lobbied the European Union to weaken CO₂ targets. A proposed ban on sales of new internal combustion cars in 2035 has faced heavy pressure from the automotive industry and resistance from EU countries with large car manufacturing.

Some senior politicians have proposed PHEVs as a potential “compromise” option to introduce in the legislation.

One independent energy economics specialist, who was not involved with the research, called the analysis a “very useful contribution” after a long period in which segments of the automotive sector argued there was insufficient data to accurately evaluate real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference in official and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel cars,” they said. “All policy changes concerning PHEVs should be implemented with extreme care and in the light of this evidence.”