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Plug-in hybrid cars release almost five times more global warming emissions than official figures indicate, as per a recent analysis.

Growing Discrepancy In Official and Actual Emissions

Data shows that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis carried out by a advocacy organization. That contrasts significantly with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers examined data from onboard energy use monitors of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” stated a senior researcher participating in the report. “That discrepancy is widening and poses a serious problem. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in battery mode compared to total distance. The team found that only 27% of driving was done in EV mode, while official assumptions assumed 84%.

Additionally, when operating in electric mode, emission amounts were well above lab estimates. This happened because electric motors were not strong sufficient to operate independently, leading to combustion motors burning gasoline for nearly a third of the distance completed in EV mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output allowed several large carmaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 extra per year in running expenses than is assumed under lab conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid cars are obviously way off the truth,” stated a transport analyst. “Consumers are being misled into thinking that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been drawn again into policy debates as carmakers have pressed the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the automotive industry and opposition from EU countries with significant automotive manufacturing.

Several high-level officials have suggested plug-in hybrids as a potential “compromise” option to introduce in the regulation.

One independent energy policy expert, who was not involved with the research, called the report a “very useful contribution” after a long period in which segments of the automotive industry argued there was insufficient data to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or diesel vehicles,” they stated. “Any regulatory changes regarding PHEVs should be made with utmost caution and in the light of that evidence.”