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Plug-in hybrid cars emit nearly 5x more planet-heating emissions than official figures indicate, as per a recent analysis.

Widening Gap In Official and Real-World Emissions

Data reveals that PHEVs release only 19% less CO₂ than traditional petrol and diesel cars, according to research carried out by a non-profit group. That contrasts significantly with lab tests, which suggested a 75% reduction in emissions.

Researchers studied information from onboard fuel consumption meters of eight hundred thousand cars registered in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a lead researcher involved in the study. “This discrepancy is growing and poses a serious problem. As a result, PHEVs emit almost as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in electric mode compared to total mileage. They found that just 27% of driving was done in electric mode, while official assumptions suggested 84%.

Additionally, when running in EV mode, pollution amounts were significantly higher than lab estimates. This occurred because electric motors were not strong enough to function independently, resulting to engines using fossil fuels for almost one-third of the travel completed in electric mode.

Regulatory and Economic Implications

Based on calculations, the underestimation of PHEV CO2 output enabled several large carmaker groups to avoid over €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ standards.

Furthermore, drivers of PHEVs would spend approximately €500 extra annually in operating expenses than is estimated under lab tests.

“The strong statements that manufacturers like to make about their plug-in hybrid cars are clearly way off the mark,” stated a transport expert. “Buyers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating costs.”

Political Debate and Automotive Pressure

Hybrid cars have recently been drawn again into political debates as automakers have lobbied the European Union to relax CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from EU countries with significant car manufacturing.

Several senior politicians have suggested plug-in hybrids as a possible “flexibility” solution to include in the regulation.

An independent energy economics specialist, who was unaffiliated with the study, called the report a “very useful addition” after years in which parts of the car sector claimed there was too little information to properly evaluate real-world CO2 output.

“These findings demonstrate, without question, that the gap in official and actual PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they said. “All policy adjustments concerning PHEVs should be made with extreme caution and considering this evidence.”