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Plug-in hybrid electric vehicles release nearly 5x more planet-heating pollution than lab-reported data indicate, according to a recent analysis.

Growing Discrepancy In Official and Real-World Emissions

Statistics shows that PHEVs emit just 19% less CO₂ than conventional gas and diesel cars, according to analysis conducted by a advocacy organization. That contrasts significantly with laboratory estimates, which suggested a three-quarters decrease in pollution.

Analysts studied information from onboard energy use monitors of 800,000 vehicles sold in Europe between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported figures are falling,” said a senior researcher participating in the study. “That discrepancy is growing and poses a serious issue. As a result, PHEVs emit almost as much as petrol cars.”

Key Reasons Driving the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of miles travelled in battery power compared to overall distance. They found that only a quarter of travel was completed in EV mode, while lab estimates assumed 84%.

Additionally, when running in electric mode, pollution levels were well above lab estimates. That occurred because EV motors were insufficiently powerful sufficient to function independently, resulting to combustion motors using fossil fuels for nearly a third of the distance covered in EV mode.

Regulatory and Financial Consequences

According to estimates, the lowballing of PHEV emissions enabled four major automaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Furthermore, owners of PHEVs could pay approximately €500 extra per year in running costs than would be assumed under lab conditions.

“The bold statements that automakers like to make about their plug-in hybrid cars are clearly way off the mark,” commented a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting money. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating costs.”

Political Discussion and Automotive Pressure

Plug-in hybrid cars have recently been brought again into political debates as automakers have pressed the EU to relax CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from member states with significant car manufacturing.

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

One independent energy policy specialist, who was not involved with the study, called the report a “highly valuable contribution” after years in which segments of the car industry argued there was insufficient information to accurately evaluate actual CO2 output.

“The results demonstrate, without question, that the gap between official and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with extreme caution and in the light of that evidence.”