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Plug-in hybrid electric vehicles release nearly five times more global warming pollution than lab-reported data show, according to a recent report.

Growing Gap In Official and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel cars, based on analysis conducted by a advocacy organization. That contrasts significantly with laboratory tests, which assumed a 75% reduction in pollution.

Researchers examined data from in-vehicle energy use meters of eight hundred thousand cars sold in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are falling,” stated a senior analyst involved in the study. “This gap is growing and creates a serious issue. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Key Factors Behind the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in battery power compared to overall mileage. They determined that just 27% of travel was done in EV mode, while lab estimates assumed 84%.

Even, when running in EV mode, pollution levels were significantly higher than official projections. That happened because EV motors were insufficiently powerful enough to operate independently, leading to engines burning gasoline for almost one-third of the distance completed in EV mode.

Policy and Financial Implications

Based on estimates, the underestimation of PHEV emissions allowed four major carmaker companies to escape over €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 more annually in running expenses than would be estimated under lab tests.

“The strong claims that automakers like to make about their PHEV cars are clearly far from the mark,” stated a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little improved than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have recently been drawn back into political discussions as automakers have pressed the EU to weaken CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and opposition from member states with significant car manufacturing.

Some senior officials have suggested plug-in hybrids as a potential “compromise” solution to include in the regulation.

An independent energy policy specialist, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which parts of the automotive industry argued there was insufficient data to accurately evaluate actual CO2 output.

“These findings show, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ output is significantly larger than for petrol or conventional cars,” they said. “Any regulatory adjustments concerning PHEVs should be made with extreme caution and considering this data.”