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Plug-in hybrid electric vehicles produce almost 5x greater global warming pollution than official figures indicate, as per a recent analysis.

Growing Gap Between Official and Real-World Emissions

Statistics reveals that PHEVs emit only one-fifth lower CO₂ than conventional gas and diesel cars, based on research conducted by a advocacy organization. That differs sharply with laboratory tests, which suggested a 75% decrease in emissions.

Analysts examined data from in-vehicle energy use meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official figures, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported emissions are decreasing,” said a senior analyst participating in the study. “This discrepancy is growing and poses a serious issue. As a result, PHEVs pollute nearly as much as gasoline cars.”

Key Factors Behind the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of miles travelled in electric power compared to total distance. They found that just 27% of travel was completed in EV mode, whereas official assumptions assumed 84%.

Even, when running in electric mode, pollution levels were significantly higher than lab estimates. This happened because electric motors were not strong enough to function independently, leading to combustion motors using fossil fuels for nearly a third of the distance covered in EV mode.

Policy and Financial Implications

Based on calculations, the underestimation of PHEV emissions enabled four large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely easing adherence with EU fleet-average CO₂ standards.

Furthermore, owners of PHEVs would spend about €500 extra annually in operating expenses than is estimated under laboratory tests.

“The strong statements that automakers often promote about their PHEV vehicles are obviously way off the truth,” commented a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Political Debate and Automotive Pressure

Hybrid cars have recently been brought again into political debates as automakers have lobbied the European Union to relax CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced intense lobbying from the car sector and resistance from EU countries with large automotive manufacturing.

Several senior politicians have proposed plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

One independent energy policy specialist, who was not involved with the research, called the analysis a “very useful addition” after a long period in which parts of the car sector claimed there was too little data to properly assess real-world CO2 output.

“The results show, beyond any doubt, that the gap in official and real-world PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or diesel vehicles,” the expert said. “All regulatory changes regarding PHEVs should be made with extreme caution and considering that evidence.”