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PHEVs produce almost five times greater planet-heating pollution than official figures indicate, according to a recent analysis.

Growing Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs emit only one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a advocacy organization. This contrasts significantly with laboratory tests, which assumed a 75% reduction in emissions.

Researchers studied data from in-vehicle energy use monitors of 800,000 cars registered in the EU between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported emissions are falling,” said a lead analyst involved in the study. “That gap is growing and poses a serious problem. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the percentage of miles driven in electric mode relative to total mileage. The team determined that only 27% of travel was completed in EV mode, whereas lab assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission levels were significantly higher than lab projections. That happened because EV motors were insufficiently powerful enough to operate independently, leading to combustion motors using gasoline for nearly a third of the travel completed in EV mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV emissions enabled several major automaker companies to avoid over €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend about €500 more annually in operating expenses than is estimated under laboratory conditions.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” commented a transport expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the environment and cutting money. Actually, PHEVs are little improved than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Debate and Automotive Pressure

Hybrid vehicles have recently been drawn again into political debates as carmakers have pressed the EU to weaken CO₂ standards. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense lobbying from the car sector and opposition from member states with significant car manufacturing.

Several high-level politicians have suggested PHEVs as a possible “flexibility” solution to introduce in the regulation.

An external energy policy specialist, who was not involved with the research, called the analysis a “highly valuable addition” after a long period in which parts of the car sector argued there was insufficient data to accurately evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ output is much, much greater than for gasoline or diesel cars,” they stated. “Any regulatory changes regarding PHEVs should be made with extreme care and considering that evidence.”