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Plug-in hybrid cars release almost five times greater global warming pollution than lab-reported data indicate, according to a recent report.

Growing Gap Between Official and Actual CO2 Output

Statistics shows that PHEVs emit only one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a non-profit organization. That contrasts sharply with laboratory tests, which suggested a three-quarters decrease in pollution.

Analysts studied data from in-vehicle energy use meters of 800,000 cars sold in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported figures are decreasing,” stated a senior researcher participating in the study. “This gap is widening and poses a serious issue. Consequently, PHEVs emit nearly as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric power relative to total distance. They determined that only 27% of driving was done in electric mode, while lab estimates suggested 84%.

Even, when running in EV mode, pollution levels were significantly higher than lab projections. This happened because EV motors were not strong enough to operate alone, resulting to engines using fossil fuels for almost one-third of the travel completed in electric mode.

Regulatory and Economic Implications

According to calculations, the lowballing of PHEV CO2 output allowed four major automaker groups to avoid over €5bn in penalties from 2021 and 2023, by falsely easing adherence with EU average fleet CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 extra per year in operating costs than would be assumed under lab tests.

“The strong statements that automakers often promote about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive expert. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Political Discussion and Automotive Pressure

Plug-in hybrid cars have recently been drawn again into policy discussions as automakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and resistance from member states with significant car manufacturing.

Some high-level officials have proposed PHEVs as a potential “compromise” solution to introduce in the legislation.

An independent energy economics expert, who was not involved with the study, called the analysis a “very useful addition” after a long period in which segments of the car industry claimed there was insufficient information to accurately assess real-world CO2 output.

“These findings demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel vehicles,” they said. “All regulatory adjustments concerning PHEVs should be made with extreme caution and in the light of this data.”