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Plug-in hybrid electric vehicles produce nearly 5x more planet-heating pollution than official figures show, according to a recent report.

Growing Gap In Lab and Actual Emissions

Data shows that PHEVs emit just 19% lower CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a advocacy group. That differs significantly with laboratory tests, which assumed a 75% decrease in pollution.

Researchers examined information from in-vehicle energy use meters of 800,000 vehicles sold in Europe between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are decreasing,” said a senior researcher involved in the report. “This discrepancy is widening and poses a significant issue. Consequently, PHEVs pollute nearly as much as petrol vehicles.”

Primary Reasons Behind the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery power relative to overall mileage. They determined that just 27% of driving was done in EV mode, while lab estimates suggested over four-fifths.

Additionally, when running in EV mode, emission levels were well above official projections. This occurred because electric motors were not strong sufficient to function independently, resulting to engines burning fossil fuels for almost one-third of the distance completed in EV mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV CO2 output allowed several large carmaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs would spend approximately €500 more annually in running costs than is estimated under lab conditions.

“The strong statements that automakers like to make about their PHEV vehicles are obviously way off the mark,” stated a transport analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are little better than regular petrol and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Political Debate 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 internal combustion vehicles in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with large car manufacturing.

Several senior officials have suggested plug-in hybrids as a possible “compromise” option to include in the regulation.

An external energy economics specialist, who was unaffiliated with the study, described the report a “highly valuable addition” after years in which segments of the car industry claimed there was insufficient data to properly assess real-world emissions.

“These findings show, beyond any doubt, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or conventional cars,” the expert stated. “Any regulatory adjustments regarding PHEVs should be made with utmost care and in the light of this evidence.”