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Plug-in hybrid cars produce almost five times greater global warming emissions than official data show, according to a recent report.

Widening Gap Between Official and Actual CO2 Output

Statistics shows that PHEVs release just one-fifth less CO₂ than traditional gas and diesel cars, based on analysis conducted by a non-profit group. This contrasts significantly with laboratory tests, which suggested a 75% decrease in emissions.

Analysts studied data from in-vehicle fuel consumption monitors of 800,000 vehicles registered in Europe from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” said a lead researcher involved in the report. “This gap is growing and creates a serious issue. Consequently, PHEVs emit almost as much as petrol cars.”

Key Reasons Behind the Discrepancy

Researchers attributed the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric mode relative to overall distance. The team determined that just 27% of travel was completed in electric mode, whereas lab assumptions suggested over four-fifths.

Even, when running in EV mode, pollution levels were well above official projections. That happened because EV motors were insufficiently powerful sufficient to function alone, leading to combustion motors using fossil fuels for nearly a third of the travel covered in electric mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed several large automaker groups to escape more than €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would pay approximately €500 extra per year in running expenses than would be estimated under lab conditions.

“The strong statements that automakers like to make about their PHEV vehicles are clearly far from the truth,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Industry Pressure

Plug-in hybrid vehicles have recently been brought again into political debates as carmakers have pressed the EU to relax CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and opposition from member states with significant car industries.

Several high-level officials have suggested PHEVs as a possible “compromise” option to introduce in the legislation.

One independent energy policy expert, who was unaffiliated with the research, described the report a “highly valuable addition” after a long period in which parts of the automotive industry argued there was insufficient data to properly assess real-world emissions.

“The results demonstrate, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel cars,” the expert stated. “Any regulatory changes concerning PHEVs should be made with extreme caution and considering this data.”