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Plug-in hybrid cars produce almost five times more global warming emissions than lab-reported data show, as per a new analysis.

Widening Gap Between Official and Actual CO2 Output

Data shows that PHEVs emit just one-fifth less CO₂ than traditional gas and diesel cars, based on research carried out by a advocacy group. This contrasts significantly with lab estimates, which assumed a three-quarters reduction in pollution.

Analysts examined information from in-vehicle energy use monitors of 800,000 vehicles registered in Europe from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” stated a lead researcher participating in the report. “That discrepancy is widening and poses a significant problem. As a result, PHEVs pollute nearly as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Analysts attributed most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers travelled in electric mode relative to total mileage. They found that just a quarter of driving was done in EV mode, while official assumptions assumed over four-fifths.

Additionally, when operating in electric mode, emission amounts were well above official estimates. That happened because EV motors were insufficiently powerful enough to function alone, resulting to engines using gasoline for nearly a third of the distance covered in electric mode.

Policy and Economic Implications

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

Additionally, owners of PHEVs could pay approximately €500 extra annually in running expenses than would be estimated under laboratory tests.

“The strong statements that manufacturers like to make about their PHEV vehicles are clearly far from the mark,” commented a transport analyst. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of energy use, CO₂ production, and running expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid vehicles have lately been drawn back into policy debates as automakers have lobbied the EU to relax CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the automotive industry and resistance from member states with significant car manufacturing.

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

One external energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable addition” after a long period in which segments of the car industry argued there was insufficient data to properly evaluate actual CO2 output.

“These findings show, beyond any doubt, that the gap between official and actual PHEV fuel consumption and CO₂ output is much, much greater than for gasoline or conventional cars,” the expert said. “All policy changes concerning PHEVs should be implemented with extreme care and in the light of that data.”