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PHEVs produce almost 5x greater planet-heating pollution than official figures indicate, according to a new analysis.

Widening Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs emit only 19% less CO₂ than conventional gas and diesel vehicles, according to research carried out by a non-profit group. That differs sharply with laboratory tests, which assumed a three-quarters decrease in pollution.

Researchers studied information from onboard fuel consumption meters of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Actual CO2 output are rising, while official figures are decreasing,” said a senior researcher involved in the report. “That discrepancy is widening and creates a significant issue. Consequently, PHEVs pollute nearly as much as gasoline cars.”

Key Reasons Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in electric mode compared to total mileage. They found that only 27% of driving was completed in electric mode, whereas official assumptions suggested over four-fifths.

Even, when operating in electric mode, emission levels were significantly higher than lab estimates. That occurred because electric motors were not strong enough to function independently, leading to engines burning gasoline for nearly one-third of the travel completed in electric mode.

Policy and Economic Implications

According to estimates, the lowballing of PHEV CO2 output allowed four large automaker groups to escape over €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 more per year in operating expenses than is estimated under lab conditions.

“The bold claims that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” commented a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are little improved than regular gas and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Political Debate and Industry Pressure

Hybrid vehicles have recently been drawn again into policy debates as automakers have pressed the European Union to relax CO₂ targets. A planned prohibition on new combustion engine cars in 2035 has faced intense pressure from the automotive industry and opposition from member states with large automotive manufacturing.

Some high-level officials have suggested plug-in hybrids as a potential “flexibility” solution to include in the regulation.

An external energy economics specialist, who was unaffiliated with the study, described the analysis a “highly valuable addition” after years in which parts of the automotive industry claimed there was too little data to accurately assess real-world CO2 output.

“These findings demonstrate, without question, that the gap between lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or diesel cars,” the expert said. “All policy adjustments concerning PHEVs should be implemented with extreme care and considering that evidence.”