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Plug-in hybrid cars release almost five times more planet-heating emissions than lab-reported figures indicate, as per a new analysis.

Widening Discrepancy Between Official and Real-World CO2 Output

Data reveals that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, based on analysis carried out by a advocacy group. This differs sharply with laboratory estimates, which assumed a 75% reduction in emissions.

Researchers studied information from in-vehicle fuel consumption meters of 800,000 cars sold in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” stated a lead analyst participating in the report. “That gap is widening and creates a serious problem. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Key Factors Behind the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in battery mode relative to total mileage. The team determined that only 27% of driving was completed in electric mode, whereas lab assumptions suggested 84%.

Even, when running in electric mode, pollution amounts were significantly higher than official estimates. This happened because EV motors were not strong sufficient to function alone, resulting to engines using fossil fuels for almost a third of the travel covered in electric mode.

Policy and Financial Implications

Based on calculations, the lowballing of PHEV emissions allowed several large automaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs could pay about €500 extra per year in running expenses than is assumed under laboratory conditions.

“The bold claims that automakers like to make about their plug-in hybrid cars are obviously far from the truth,” stated a automotive expert. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of energy use, CO₂ emissions, and running costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid cars have lately been brought again into policy discussions as carmakers have lobbied the EU to weaken CO₂ targets. A proposed ban on new combustion engine cars in 2035 has faced heavy lobbying from the car sector and opposition from EU countries with significant automotive manufacturing.

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

An independent energy policy expert, who was not involved with the study, called the analysis a “very useful addition” after years in which parts of the car industry argued there was insufficient information to properly evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” they said. “All policy adjustments regarding PHEVs should be made with utmost care and considering that data.”