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Plug-in hybrid electric vehicles produce nearly 5x greater planet-heating pollution than official data show, according to a new analysis.

Growing Gap In Official and Actual Emissions

Statistics shows that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a advocacy group. That contrasts significantly with lab estimates, which assumed a 75% decrease in pollution.

Analysts studied data from onboard fuel consumption monitors of eight hundred thousand cars registered in Europe from 2021 and 2023. The team found that actual CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported emissions are decreasing,” stated a senior researcher participating in the report. “This gap is growing and poses a significant issue. As a result, PHEVs emit nearly as heavily as petrol vehicles.”

Primary Factors Driving the Discrepancy

Analysts linked most of the gap to inflated estimates of the “utility factor” – the percentage of miles driven in electric 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 running in electric mode, pollution amounts were well above official estimates. That happened because electric motors were not strong enough to function independently, resulting to engines burning gasoline for almost a third of the travel covered in electric mode.

Policy and Economic Consequences

Based on calculations, the underestimation of PHEV CO2 output allowed four large carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would spend approximately €500 more per year in running costs than would be estimated under laboratory conditions.

“The strong statements that automakers like to make about their PHEV vehicles are clearly way off the mark,” stated a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. In reality, PHEVs are only slightly better than standard gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating costs.”

Political Debate and Industry Pressure

Hybrid vehicles have lately been drawn back into political discussions as automakers have pressed the EU to relax CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy lobbying from the car sector and opposition from member states with large automotive manufacturing.

Some senior officials have suggested plug-in hybrids as a potential “compromise” option to include in the legislation.

An independent energy economics expert, who was not involved with the research, described the analysis a “very useful contribution” after a long period in which segments of the car sector argued there was insufficient information to properly assess actual emissions.

“The results show, without question, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” they stated. “Any policy changes concerning PHEVs should be made with utmost care and considering this data.”