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Plug-in hybrid cars produce almost five times greater global warming emissions than lab-reported data show, according to a recent report.

Growing Discrepancy In Official and Actual CO2 Output

Data reveals that PHEVs release only 19% less CO₂ than traditional petrol and diesel vehicles, based on analysis carried out by a non-profit organization. This differs significantly with lab estimates, which assumed a 75% reduction in emissions.

Researchers studied information from in-vehicle energy use monitors of eight hundred thousand cars sold in Europe between 2021 and 2023. The team discovered that actual CO₂ output from PHEVs in 2023 were nearly five times greater than official figures, increased from three and a half times in 2021.

“Real-world emissions are increasing, while official figures are falling,” stated a lead researcher involved in the study. “That gap is widening and poses a serious issue. As a result, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to total distance. The team determined that just a quarter of driving was done in electric mode, whereas lab assumptions suggested over four-fifths.

Additionally, when running in EV mode, emission amounts were significantly higher than lab estimates. This happened because EV motors were not strong enough to function alone, leading to engines using fossil fuels for almost a third of the travel covered in EV mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV emissions allowed four major automaker companies to escape more than €5bn in fines from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ standards.

Additionally, drivers of PHEVs could pay about €500 extra per year in operating costs than is estimated under lab tests.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive expert. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are little better than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Automotive Pressure

Hybrid cars have recently been brought back into political discussions as carmakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on new combustion engine cars in 2035 has faced heavy pressure from the car sector and resistance from member states with large automotive manufacturing.

Some high-level politicians have suggested plug-in hybrids as a potential “flexibility” option to include in the regulation.

An external energy policy specialist, who was not involved with the research, described the analysis a “very useful addition” after years in which segments of the car industry argued there was insufficient data to accurately assess actual emissions.

“The results demonstrate, beyond any doubt, that the gap between lab and real-world PHEV energy use 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 care and in the light of this evidence.”