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PHEVs produce nearly five times greater global warming pollution than lab-reported data indicate, according to a recent analysis.

Growing Gap Between Official and Real-World CO2 Output

Data reveals that PHEVs emit only 19% lower CO₂ than traditional gas and diesel cars, according to analysis conducted by a non-profit group. That differs sharply with laboratory tests, which suggested a three-quarters decrease in pollution.

Researchers studied data from onboard energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Actual emissions are increasing, while official emissions are falling,” stated a lead researcher involved in the report. “That gap is growing and creates a significant issue. As a result, PHEVs emit nearly as heavily as gasoline cars.”

Primary Reasons Behind the Discrepancy

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the percentage of kilometers travelled in electric mode compared to total distance. They determined that just 27% of driving was done in electric mode, while official estimates suggested over four-fifths.

Additionally, when running in electric mode, pollution amounts were significantly higher than official projections. That happened because EV motors were not strong enough to function independently, leading to combustion motors using fossil fuels for almost a third of the travel covered in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV emissions allowed four large carmaker groups to escape more than €5bn in penalties from 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 extra annually in operating costs than is estimated under lab conditions.

“The strong claims that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” stated a transport analyst. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Debate and Industry Pressure

Plug-in hybrid cars have recently been brought again into political debates as automakers have lobbied the European Union to weaken CO₂ standards. A planned prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive sector and resistance from member states with significant car industries.

Some senior politicians have proposed PHEVs as a potential “compromise” solution to introduce in the regulation.

One external energy economics specialist, who was unaffiliated with the research, described the analysis a “very useful contribution” after years in which segments of the car industry argued there was too little data to accurately assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional cars,” the expert stated. “All policy adjustments regarding PHEVs should be made with utmost caution and considering that data.”