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PHEVs release almost 5x more planet-heating pollution than lab-reported data indicate, as per a new analysis.

Widening Discrepancy In Lab and Real-World CO2 Output

Data shows that PHEVs release just 19% lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a advocacy organization. That differs sharply with laboratory estimates, which suggested a 75% reduction in emissions.

Analysts studied data from onboard energy use monitors of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” stated a senior researcher participating in the study. “This gap is growing and poses a serious issue. Consequently, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Analysts linked the majority of the difference to overestimates of the “utility factor” – the percentage of kilometers driven in electric power compared to total mileage. The team found that just a quarter of travel was completed in electric mode, whereas lab estimates assumed over four-fifths.

Additionally, when operating in electric mode, pollution amounts were significantly higher than official projections. This occurred because EV motors were insufficiently powerful sufficient to operate alone, leading to engines using fossil fuels for almost a third of the travel covered in EV mode.

Regulatory and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output allowed four large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs would spend approximately €500 more per year in operating costs than is assumed under laboratory tests.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the mark,” stated a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little improved than regular gas and diesel cars in terms of energy consumption, CO₂ production, and running expenses.”

Political Discussion and Automotive Pressure

Hybrid vehicles have recently been drawn again into political debates as carmakers have lobbied the EU to relax CO₂ targets. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with significant car industries.

Some senior officials have proposed PHEVs as a potential “flexibility” solution to include in the regulation.

One external energy economics expert, who was unaffiliated with the research, called the report a “very useful addition” after years in which segments of the automotive sector argued there was insufficient data to accurately evaluate real-world emissions.

“The results show, without question, that the difference between official and actual PHEV energy use and CO₂ emissions is much, much greater than for gasoline or conventional vehicles,” the expert said. “Any regulatory changes regarding PHEVs should be made with utmost caution and in the light of that evidence.”