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PHEVs produce nearly 5x more global warming emissions than lab-reported figures show, according to a new analysis.

Growing Gap Between Official and Actual CO2 Output

Statistics reveals that PHEVs release only 19% lower CO₂ than conventional gas and diesel vehicles, based on research carried out by a non-profit group. That contrasts sharply with laboratory tests, which suggested a three-quarters decrease in pollution.

Researchers studied information from in-vehicle energy use meters of 800,000 cars registered in Europe between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are decreasing,” stated a senior researcher participating in the study. “This gap is widening and creates a significant problem. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Key Factors Behind the Discrepancy

Researchers attributed most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery power relative to total distance. The team found that just a quarter of driving was completed in EV mode, while lab estimates assumed 84%.

Even, when running in electric mode, emission amounts were well above lab projections. That happened because EV motors were not strong enough to function independently, resulting to engines burning fossil fuels for nearly a third of the travel completed in electric mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV emissions enabled four large carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs could pay approximately €500 extra per year in running costs than is assumed under laboratory conditions.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are obviously far from the mark,” stated a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little improved than regular petrol and diesel cars in terms of energy use, CO₂ production, and running costs.”

Political Discussion and Industry Pressure

Plug-in hybrid cars have lately been brought again into political discussions as carmakers have pressed the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and opposition from EU countries with significant automotive manufacturing.

Some senior officials have suggested plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

An independent energy economics specialist, who was unaffiliated with the research, called the report a “very useful contribution” after a long period in which parts of the car industry argued there was insufficient information to accurately evaluate real-world emissions.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel cars,” the expert stated. “Any policy adjustments regarding PHEVs should be implemented with utmost caution and considering that data.”