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Plug-in hybrid electric vehicles emit almost 5x more planet-heating emissions than official data show, according to a recent analysis.

Growing Discrepancy In Official and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than traditional gas and diesel cars, according to analysis carried out by a non-profit organization. This contrasts sharply with laboratory tests, which assumed a 75% reduction in pollution.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 cars registered in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” stated a lead analyst involved in the study. “That discrepancy is widening and creates a significant issue. As a result, PHEVs emit almost as much as petrol vehicles.”

Key Factors Behind the Discrepancy

Researchers attributed the majority of the gap to overestimates of the “utility factor” – the percentage of miles driven in electric mode compared to total mileage. They found that just a quarter of travel was completed in electric mode, whereas official estimates suggested 84%.

Additionally, when running in electric mode, pollution amounts were well above official projections. That happened because electric motors were not strong sufficient to operate independently, resulting to engines using fossil fuels for nearly one-third of the distance covered in EV mode.

Policy and Financial Consequences

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

Additionally, drivers of PHEVs could pay approximately €500 extra annually in operating expenses than would be estimated under lab conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid cars are obviously far from the truth,” commented a transport analyst. “Buyers are being duped into believing that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been brought again into political debates as carmakers have pressed the European Union to relax CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with large automotive industries.

Some senior politicians have proposed plug-in hybrids as a potential “flexibility” solution to introduce in the legislation.

An external energy economics expert, who was unaffiliated with the research, described the report a “very useful contribution” after a long period in which segments of the automotive industry claimed there was insufficient data to accurately evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in lab and real-world PHEV energy use and CO₂ emissions is significantly larger than for gasoline or diesel vehicles,” the expert said. “Any regulatory changes regarding PHEVs should be made with utmost caution and in the light of that data.”