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Plug-in hybrid electric vehicles produce almost 5x greater global warming pollution than lab-reported figures show, according to a new analysis.

Growing Discrepancy In Official and Real-World Emissions

Statistics shows that PHEVs emit just 19% lower CO₂ than traditional gas and diesel vehicles, according to research carried out by a non-profit organization. That contrasts sharply with laboratory tests, which suggested a 75% reduction in emissions.

Analysts studied data from in-vehicle energy use meters of eight hundred thousand cars sold in the EU between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are falling,” said a senior researcher involved in the report. “This discrepancy is widening and creates a serious issue. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery mode compared to total distance. The team determined that only 27% of travel was completed in EV mode, whereas official assumptions suggested over four-fifths.

Even, when running in EV mode, pollution levels were significantly higher than lab estimates. That happened because electric motors were not strong enough to operate alone, resulting to engines using fossil fuels for nearly one-third of the distance covered in EV mode.

Regulatory and Economic Implications

According to estimates, the underestimation of PHEV CO2 output enabled several major automaker companies to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 extra per year in operating expenses than is estimated under laboratory conditions.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little improved than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and running costs.”

Political Debate and Automotive Pressure

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 heavy lobbying from the automotive sector and opposition from member states with significant automotive manufacturing.

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

An external energy policy expert, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which segments of the automotive sector argued there was too little information to accurately evaluate actual emissions.

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