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Plug-in hybrid electric vehicles emit almost five times greater planet-heating emissions than lab-reported data indicate, as per a recent analysis.

Widening Gap In Official and Actual Emissions

Statistics shows that PHEVs release just 19% less CO₂ than conventional gas and diesel cars, based on research conducted by a non-profit group. That contrasts significantly with lab tests, which suggested a three-quarters reduction in pollution.

Researchers studied information from in-vehicle energy use monitors of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual emissions are increasing, while lab-reported emissions are decreasing,” said a senior researcher involved in the report. “This gap is growing and poses a serious issue. Consequently, PHEVs pollute nearly as much as petrol cars.”

Key Factors Behind the Emissions Gap

Analysts attributed most of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric mode compared to total mileage. They determined that only a quarter of driving was done in EV mode, while official assumptions suggested 84%.

Additionally, when running in EV mode, pollution amounts were well above lab estimates. That occurred because electric motors were not strong enough to function alone, leading to engines using gasoline for almost a third of the distance covered in electric mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output allowed four major automaker groups to escape over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 more per year in running expenses than would be assumed under lab conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the mark,” stated a automotive analyst. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Hybrid cars have recently been drawn again into policy discussions as carmakers have lobbied the EU to relax CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from EU countries with significant automotive manufacturing.

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

An external energy economics specialist, who was not involved with the research, called the report a “very useful addition” after a long period in which segments of the car sector claimed there was insufficient data to properly evaluate real-world emissions.

“These findings show, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel vehicles,” the expert stated. “All regulatory adjustments regarding PHEVs should be implemented with utmost care and in the light of this data.”