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Plug-in hybrid electric vehicles produce nearly 5x greater global warming emissions than lab-reported data show, as per a new analysis.

Growing Gap Between Official and Actual CO2 Output

Statistics reveals that PHEVs release only 19% less CO₂ than conventional petrol and diesel vehicles, based on research conducted by a non-profit group. This contrasts significantly with laboratory estimates, which assumed a 75% reduction in pollution.

Researchers studied data from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, up from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” said a senior analyst participating in the report. “This discrepancy is widening and creates a serious problem. As a result, PHEVs pollute almost as heavily as gasoline cars.”

Primary Factors Driving the Discrepancy

Analysts linked most of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric power relative to total distance. The team determined that just 27% of driving was completed in electric mode, whereas lab estimates suggested over four-fifths.

Additionally, when operating in electric mode, pollution amounts were well above official estimates. This occurred because EV motors were not strong sufficient to operate independently, leading to combustion motors burning fossil fuels for almost a third of the distance covered in EV mode.

Policy and Financial Consequences

According to estimates, the lowballing of PHEV CO2 output enabled several large automaker companies to avoid over €5bn in penalties between 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 extra per year in operating costs than is assumed under laboratory tests.

“The strong claims that automakers often promote about their plug-in hybrid cars are clearly way off the truth,” commented a automotive analyst. “Buyers are being misled into thinking that by buying a PHEV, they are helping the environment and saving costs. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and running expenses.”

Political Discussion and Automotive Lobbying

Plug-in hybrid cars have recently been drawn back into political debates as automakers have pressed the EU to relax CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced heavy pressure from the car sector and opposition from member states with large car industries.

Some high-level officials have suggested plug-in hybrids as a possible “compromise” solution to include in the regulation.

An independent energy policy expert, who was not involved with the research, called the analysis a “very useful contribution” after years in which parts of the automotive industry argued there was too little data to accurately evaluate actual emissions.

“The results show, beyond any doubt, that the difference between lab and real-world PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” the expert stated. “All policy changes regarding PHEVs should be implemented with utmost care and in the light of this data.”