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Plug-in hybrid electric vehicles release nearly five times more planet-heating pollution than official data show, according to a recent report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Statistics shows that PHEVs emit only one-fifth lower CO₂ than conventional gas and diesel cars, according to analysis conducted by a non-profit organization. This contrasts significantly with laboratory estimates, which suggested a three-quarters reduction in pollution.

Researchers studied information from onboard fuel consumption monitors of 800,000 cars sold in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab figures, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are decreasing,” stated a senior researcher participating in the report. “This discrepancy is growing and creates a significant problem. As a result, PHEVs emit nearly as much as gasoline cars.”

Primary Factors Driving the Discrepancy

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in electric mode relative to total distance. They determined that only 27% of travel was completed in electric mode, whereas official assumptions suggested over four-fifths.

Even, when operating in EV mode, pollution levels were well above official projections. This occurred because EV motors were insufficiently powerful sufficient to function independently, leading to engines burning fossil fuels for almost a third of the travel covered in EV mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV emissions enabled several large automaker companies to avoid more than €5bn in penalties between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Furthermore, owners of PHEVs would pay approximately €500 more per year in running expenses than is assumed under laboratory tests.

“The bold claims that automakers like to make about their plug-in hybrid vehicles are obviously way off the mark,” commented a transport expert. “Consumers are being duped into believing that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are little better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been drawn back into political discussions as automakers have lobbied the European Union to weaken CO₂ standards. A proposed ban on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with significant car industries.

Some high-level officials have proposed plug-in hybrids as a potential “flexibility” solution to include in the regulation.

An independent energy policy expert, who was unaffiliated with the research, described the report a “highly valuable contribution” after years in which parts of the car industry claimed there was too little data to accurately assess actual CO2 output.

“These findings demonstrate, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or conventional vehicles,” they stated. “All regulatory adjustments concerning PHEVs should be implemented with extreme care and considering that data.”