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Plug-in hybrid electric vehicles release almost five times more planet-heating emissions than official data indicate, as per a recent analysis.

Widening Gap Between Official and Actual CO2 Output

Data reveals that PHEVs emit just 19% less CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a advocacy group. That differs sharply with lab tests, which assumed a 75% reduction in emissions.

Researchers examined information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in Europe between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are falling,” stated a lead analyst participating in the study. “That discrepancy is widening and creates a serious problem. As a result, PHEVs emit nearly as much as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in electric power relative to total distance. They determined that just 27% of driving was completed in EV mode, whereas lab assumptions assumed 84%.

Additionally, when running in EV mode, pollution amounts were well above lab projections. That happened because EV motors were insufficiently powerful sufficient to function alone, leading to combustion motors burning fossil fuels for almost a third of the travel completed in EV mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions enabled four large carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 more per year in running costs than would be assumed under lab tests.

“The strong statements that automakers often promote about their PHEV vehicles are clearly way off the truth,” stated a automotive analyst. “Consumers are being duped into believing that by buying a PHEV, they are helping the environment and cutting costs. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have recently been drawn back into political debates as automakers have lobbied the EU to weaken CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense lobbying from the automotive sector and opposition from member states with significant automotive industries.

Several senior politicians have suggested PHEVs as a possible “compromise” solution to introduce in the legislation.

An independent energy economics specialist, who was unaffiliated with the research, called the report a “very useful contribution” after years in which parts of the car sector claimed there was insufficient data to accurately assess real-world CO2 output.

“These findings show, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional vehicles,” the expert stated. “Any regulatory changes concerning PHEVs should be implemented with utmost caution and in the light of this data.”