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Plug-in hybrid cars emit nearly five times more global warming pollution than lab-reported data show, as per a new analysis.

Widening Gap Between Official and Actual CO2 Output

Data shows that PHEVs release only 19% less CO₂ than traditional gas and diesel cars, based on research conducted by a advocacy organization. That contrasts sharply with lab estimates, which suggested a 75% reduction in pollution.

Analysts studied information from in-vehicle fuel consumption monitors of eight hundred thousand cars sold in Europe from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while official emissions are falling,” said a senior analyst involved in the study. “This discrepancy is widening and creates a serious issue. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Key Factors Driving the Discrepancy

Researchers attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers driven in battery power compared to overall distance. The team found that just 27% of travel was completed in EV mode, whereas official assumptions assumed 84%.

Even, when operating in electric mode, pollution levels were significantly higher than official estimates. That happened because EV motors were not strong enough to function independently, leading to engines burning fossil fuels for almost a third of the travel completed in electric mode.

Policy and Financial Consequences

According to calculations, the lowballing of PHEV emissions allowed several large automaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 more annually in operating expenses than would be assumed under lab conditions.

“The strong statements that automakers like to make about their PHEV vehicles are clearly far from the mark,” commented a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and running expenses.”

Political Debate and Automotive Pressure

Hybrid vehicles have recently been drawn back into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A proposed ban on new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large car manufacturing.

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

One independent energy economics expert, who was not involved with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the car sector argued there was too little information to properly assess actual CO2 output.

“These findings show, without question, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional vehicles,” the expert stated. “Any policy adjustments regarding PHEVs should be made with extreme caution and considering this data.”