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Plug-in hybrid cars release nearly 5x more planet-heating emissions than lab-reported data indicate, as per a recent analysis.

Growing Discrepancy In Lab and Real-World CO2 Output

Data reveals that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, based on research conducted by a advocacy organization. This differs sharply with laboratory tests, which suggested a 75% reduction in emissions.

Researchers examined data from in-vehicle fuel consumption meters of 800,000 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 estimates, increased from 3.5 times in 2021.

“Actual CO2 output are rising, while official emissions are falling,” said a senior researcher participating in the study. “That discrepancy is growing and creates a serious issue. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Key Reasons Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in battery mode relative to total distance. The team determined that only 27% of driving was completed in electric mode, whereas official assumptions assumed 84%.

Additionally, when running in electric mode, pollution levels were significantly higher than official projections. That occurred because EV motors were insufficiently powerful sufficient to function alone, resulting to engines using gasoline for almost one-third of the travel completed in EV mode.

Policy and Financial Consequences

Based on estimates, the lowballing of PHEV emissions allowed several major carmaker companies to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Additionally, owners of PHEVs would pay about €500 extra annually in operating costs than is assumed under lab conditions.

“The strong statements that manufacturers like to make about their PHEV cars are obviously way off the truth,” commented a transport analyst. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. Actually, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Discussion and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into policy discussions as carmakers have pressed the EU to weaken CO₂ targets. A planned prohibition on sales of new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with large automotive manufacturing.

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

One independent energy economics specialist, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which segments of the automotive sector argued there was too little data to properly evaluate real-world emissions.

“The results demonstrate, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ emissions is much, much larger than for petrol or diesel vehicles,” they stated. “All policy changes concerning PHEVs should be implemented with utmost caution and considering that evidence.”