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Plug-in hybrid electric vehicles produce almost five times greater global warming pollution than official figures indicate, according to a recent analysis.

Growing Gap Between Lab and Actual Emissions

Statistics reveals that PHEVs release only 19% less CO₂ than conventional petrol and diesel vehicles, according to research carried out by a advocacy organization. That differs significantly with laboratory estimates, which assumed a 75% reduction in emissions.

Researchers studied data from in-vehicle energy use monitors of eight hundred thousand cars registered in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than lab figures, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” said a lead researcher involved in the study. “That gap is growing and creates a significant issue. Consequently, PHEVs emit almost as heavily as gasoline cars.”

Key Reasons Behind the Discrepancy

Researchers linked the majority of the difference to inflated estimates of the “electric driving share” – the ratio of kilometers driven in electric mode relative to total distance. They determined that just 27% of driving was done in electric mode, whereas lab estimates suggested 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than official estimates. This happened because EV motors were not strong enough to operate independently, leading to combustion motors using fossil fuels for nearly a third of the distance completed in EV mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled several large carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 extra annually in operating costs than would be estimated under laboratory tests.

“The bold statements that manufacturers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a transport analyst. “Buyers are being duped into thinking that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Discussion and Automotive Lobbying

Hybrid cars have recently been drawn back into political discussions as automakers have lobbied the European Union to relax CO₂ targets. A proposed prohibition on new internal combustion vehicles in 2035 has faced intense lobbying from the car industry and opposition from member states with large car manufacturing.

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

An external energy policy expert, who was unaffiliated with the research, described the report a “highly valuable contribution” after years in which parts of the automotive industry argued there was insufficient data to accurately evaluate actual emissions.

“These findings show, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional vehicles,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with utmost care and in the light of that data.”