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Plug-in hybrid electric vehicles emit nearly five times more global warming pollution than lab-reported figures show, as per a recent analysis.

Growing Discrepancy In Lab and Real-World Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional petrol and diesel vehicles, based on research conducted by a non-profit group. That contrasts significantly with laboratory tests, which suggested a 75% decrease in pollution.

Researchers examined data from onboard energy use monitors of 800,000 vehicles registered in the EU between 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are falling,” said a lead analyst participating in the report. “That discrepancy is growing and creates a significant problem. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Key Factors Behind the Discrepancy

Researchers linked most of the gap to overestimates of the “electric driving share” – the ratio of kilometers driven in battery power compared to total mileage. They found that just 27% of driving was completed in electric mode, whereas official assumptions assumed 84%.

Even, when operating in electric mode, pollution levels were well above lab projections. This happened because EV motors were not strong sufficient to operate alone, leading to engines burning gasoline for almost a third of the travel covered in EV mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output enabled four large carmaker companies to escape more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 more annually in running expenses than would be assumed under lab conditions.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the mark,” stated a automotive analyst. “Consumers are being misled into thinking that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little better than standard gas and diesel vehicles in terms of fuel use, CO₂ production, and operating costs.”

Policy Debate and Industry Pressure

Plug-in hybrid vehicles have recently been drawn back into policy discussions as automakers have lobbied the European Union to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the car sector and opposition from EU countries with large automotive manufacturing.

Some senior politicians have proposed plug-in hybrids as a possible “flexibility” option to introduce in the regulation.

One external energy economics specialist, who was unaffiliated with the research, called the report a “very useful addition” after a long period in which segments of the automotive industry argued there was insufficient data to properly evaluate actual CO2 output.

“The results demonstrate, without question, that the gap between lab and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or conventional cars,” the expert said. “All policy adjustments concerning PHEVs should be made with utmost caution and considering that evidence.”