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Plug-in hybrid electric vehicles produce almost 5x greater global warming pollution than official figures show, according to a new report.

Growing Gap Between Official and Real-World Emissions

Data shows that PHEVs emit just one-fifth lower CO₂ than conventional gas and diesel vehicles, based on research conducted by a non-profit group. That differs significantly with laboratory tests, which suggested a 75% decrease in emissions.

Researchers studied data from in-vehicle fuel consumption meters of 800,000 cars registered in Europe between 2021 and 2023. The team discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” said a lead analyst involved in the report. “That gap is widening and poses a serious problem. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Factors Driving the Emissions Gap

Researchers linked the majority of the difference to overestimates of the “electric driving share” – the percentage of miles driven in electric mode relative to total mileage. They found that just 27% of travel was done in electric mode, whereas official estimates assumed 84%.

Even, when running in EV mode, emission amounts were well above lab projections. That happened because EV motors were insufficiently powerful sufficient to operate alone, resulting to engines using gasoline for nearly one-third of the distance covered in EV mode.

Regulatory and Financial Implications

Based on calculations, the lowballing of PHEV CO2 output enabled four major carmaker groups to avoid more than €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay approximately €500 more per year in running expenses than is estimated under lab tests.

“The bold statements that automakers often promote about their PHEV vehicles are clearly way off the mark,” commented a automotive analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of energy consumption, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been brought back into policy discussions as automakers have lobbied the EU to relax CO₂ targets. A planned ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the car industry and opposition from member states with large car industries.

Several high-level officials have proposed PHEVs as a potential “compromise” solution to include in the regulation.

One external energy economics expert, who was not involved with the study, described the report a “highly valuable addition” after a long period in which segments of the car sector claimed there was insufficient information to properly evaluate real-world CO2 output.

“The results demonstrate, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is much, much larger than for gasoline or conventional cars,” they said. “Any policy adjustments concerning PHEVs should be implemented with extreme care and considering this data.”