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PHEVs release almost five times more planet-heating emissions than official data indicate, according to a new report.

Widening Discrepancy In Lab and Real-World CO2 Output

Statistics shows that PHEVs release only 19% lower CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a advocacy organization. That contrasts significantly with laboratory estimates, which suggested a 75% reduction in pollution.

Researchers examined information from in-vehicle energy use meters of 800,000 vehicles sold in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” stated a lead researcher participating in the report. “This discrepancy is widening and creates a significant problem. Consequently, PHEVs pollute nearly as much as petrol cars.”

Primary Factors Behind the Discrepancy

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the percentage of miles travelled in battery mode relative to overall distance. They found that only 27% of travel was completed in EV mode, while lab estimates assumed over four-fifths.

Even, when running in EV mode, pollution amounts were well above official estimates. This happened because EV motors were not strong enough to function alone, leading to combustion motors using fossil fuels for almost a third of the travel completed in EV mode.

Regulatory and Economic Consequences

According to estimates, the lowballing of PHEV CO2 output allowed several large automaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend about €500 more per year in operating expenses than is assumed under laboratory tests.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a transport expert. “Buyers are being misled into believing that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel use, CO₂ emissions, and running costs.”

Political Discussion and Automotive Lobbying

Hybrid vehicles have lately been drawn back into policy debates as automakers have lobbied the European Union to relax CO₂ standards. A planned ban on new internal combustion cars in 2035 has faced heavy pressure from the automotive sector and resistance from EU countries with large car manufacturing.

Some senior officials have suggested PHEVs as a potential “flexibility” solution to introduce in the regulation.

An independent energy policy expert, who was unaffiliated with the research, called the report a “highly valuable addition” after a long period in which segments of the car sector argued there was insufficient data to properly evaluate real-world emissions.

“These findings show, without question, that the gap in lab and actual PHEV energy use and CO₂ output is much, much larger than for gasoline or diesel cars,” the expert stated. “All policy changes regarding PHEVs should be made with extreme caution and considering that data.”