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Plug-in hybrid cars produce nearly five times greater planet-heating emissions than lab-reported figures indicate, according to a new analysis.

Widening Discrepancy In Official and Actual CO2 Output

Data reveals that PHEVs emit only 19% less CO₂ than traditional petrol and diesel vehicles, according to analysis conducted by a advocacy organization. This contrasts sharply with lab estimates, which assumed a 75% reduction in pollution.

Analysts studied information from onboard fuel consumption meters of eight hundred thousand vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab figures, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while official emissions are decreasing,” said a lead researcher participating in the study. “That gap is widening and poses a significant issue. As a result, PHEVs emit almost as much as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Analysts attributed the majority of the gap to overestimates of the “utility factor” – the percentage of miles driven in battery power relative to total distance. They found that only a quarter of travel was done in electric mode, while official assumptions suggested 84%.

Even, when operating in electric mode, pollution levels were significantly higher than lab projections. That happened because electric motors were not strong enough to function alone, leading to combustion motors burning fossil fuels for almost one-third of the distance completed in electric mode.

Policy and Financial Implications

According to estimates, the lowballing of PHEV emissions enabled several major carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ standards.

Additionally, owners of PHEVs would spend about €500 extra annually in operating expenses than would be assumed under lab conditions.

“The bold statements that automakers like to make about their plug-in hybrid vehicles are obviously far from the mark,” commented a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the planet and saving money. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn back into political debates as carmakers have pressed the European Union to relax CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced intense lobbying from the car industry and resistance from EU countries with significant automotive industries.

Some senior politicians have suggested plug-in hybrids as a potential “compromise” solution to include in the regulation.

One external energy policy specialist, who was unaffiliated with the study, described the report a “highly valuable contribution” after a long period in which parts of the car industry argued there was insufficient information to accurately evaluate real-world emissions.

“These findings demonstrate, without question, that the gap in lab and real-world PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel cars,” they stated. “Any regulatory adjustments regarding PHEVs should be implemented with extreme care and considering this evidence.”