Plug in Hybrid Cars Pollute Almost as Much as Petrol Cars, Study Finds

Plug-in hybrid cars emit almost five times greater planet-heating pollution than lab-reported figures show, as per a recent analysis.

Widening Gap Between Official and Real-World CO2 Output

Data shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, based on research conducted by a advocacy group. This differs sharply with lab estimates, which assumed a three-quarters decrease in emissions.

Researchers studied data from onboard fuel consumption meters of eight hundred thousand cars sold in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab figures, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” said a lead analyst participating in the study. “This discrepancy is widening and creates a significant issue. As a result, PHEVs emit nearly as much as gasoline cars.”

Primary Factors Behind the Discrepancy

Researchers attributed most of the gap to overestimates of the “electric driving share” – the percentage of kilometers driven in battery power relative to overall distance. They found that only 27% of travel was done in EV mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, emission levels were significantly higher than lab estimates. That occurred because EV motors were not strong sufficient to function alone, leading to combustion motors using gasoline for nearly a third of the distance covered in EV mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV emissions enabled four major automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay about €500 extra per year in operating costs than is assumed under lab tests.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are obviously far from the truth,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are only slightly better than regular petrol and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running expenses.”

Policy Discussion and Industry Pressure

Hybrid cars have recently been brought again into policy debates as carmakers have lobbied the EU to relax CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with large automotive industries.

Some high-level politicians have suggested PHEVs as a potential “flexibility” option to include in the regulation.

One independent energy policy specialist, who was unaffiliated with the research, called the report a “highly valuable contribution” after a long period in which segments of the car industry claimed there was insufficient data to properly evaluate real-world emissions.

“These findings show, without question, that the gap in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or diesel cars,” they said. “All regulatory adjustments regarding PHEVs should be implemented with utmost care and considering that evidence.”