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Plug-in hybrid cars emit almost five times greater global warming emissions than lab-reported data indicate, according to a new analysis.

Growing Gap In Lab and Real-World CO2 Output

Statistics shows that PHEVs release just 19% lower CO₂ than traditional gas and diesel vehicles, based on research conducted by a non-profit organization. That differs sharply with lab estimates, which suggested a three-quarters decrease in pollution.

Analysts examined information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles registered in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Actual emissions are rising, while official emissions are decreasing,” said a senior researcher participating in the report. “This discrepancy is widening and poses a significant issue. As a result, PHEVs emit almost as much as petrol cars.”

Primary Reasons Behind the Discrepancy

Researchers linked the majority of the difference to overestimates of the “utility factor” – the ratio of miles driven in electric power compared to overall mileage. They determined that just a quarter of travel was done in EV mode, whereas official estimates suggested over four-fifths.

Additionally, when operating in electric mode, emission amounts were well above official estimates. That happened because electric motors were not strong sufficient to operate alone, resulting to combustion motors using fossil fuels for nearly one-third of the travel completed in electric mode.

Regulatory and Financial Implications

According to calculations, the lowballing of PHEV emissions enabled four large carmaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, owners of PHEVs could spend approximately €500 extra annually in operating costs than is assumed under lab conditions.

“The bold statements that automakers often promote about their PHEV vehicles are clearly far from the mark,” commented a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the planet and saving money. Actually, PHEVs are little improved than standard gas and diesel vehicles in terms of energy consumption, CO₂ production, and operating expenses.”

Political Discussion and Automotive Lobbying

Plug-in hybrid vehicles have lately been brought again into policy debates as automakers have pressed the EU to weaken CO₂ targets. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced heavy lobbying from the car sector and opposition from member states with large car manufacturing.

Several senior politicians have proposed plug-in hybrids as a possible “compromise” solution to introduce in the regulation.

One independent energy economics specialist, who was unaffiliated with the research, described the report a “very useful addition” after a long period in which parts of the automotive industry claimed there was insufficient data to accurately assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for petrol or diesel cars,” they stated. “Any regulatory changes regarding PHEVs should be implemented with utmost caution and considering this data.”