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Plug-in hybrid electric vehicles produce nearly five times more planet-heating emissions than lab-reported figures show, according to a new report.

Growing Discrepancy Between Lab and Actual Emissions

Data shows that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel vehicles, according to analysis conducted by a advocacy organization. That differs sharply with lab tests, which suggested a 75% reduction in emissions.

Analysts studied information from in-vehicle energy use monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, increased from three and a half times in 2021.

“Actual CO2 output are increasing, while official emissions are falling,” stated a senior analyst involved in the study. “That gap is growing and creates a significant problem. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Primary Reasons Behind the Discrepancy

Researchers attributed the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers driven in battery mode relative to overall distance. They found that only a quarter of driving was completed in electric mode, whereas official assumptions suggested over four-fifths.

Even, when running in electric mode, emission levels were well above lab projections. This occurred because electric motors were not strong enough to function independently, leading to engines using gasoline for almost one-third of the distance completed in electric mode.

Regulatory and Financial Consequences

Based on calculations, the lowballing of PHEV CO2 output allowed four major automaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with European Union fleet-average CO₂ standards.

Furthermore, owners of PHEVs could spend approximately €500 more annually in running expenses than would be estimated under lab tests.

“The strong claims that manufacturers like to make about their PHEV vehicles are obviously way off the mark,” commented a automotive analyst. “Buyers are being misled into believing that by buying a PHEV, they are helping the planet and cutting money. In reality, PHEVs are only slightly better than regular gas and diesel vehicles in terms of fuel consumption, CO₂ production, and operating expenses.”

Political Debate and Industry Lobbying

Hybrid cars have recently been drawn back into political debates as carmakers have pressed the EU to relax CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and resistance from EU countries with significant car manufacturing.

Several senior politicians have proposed plug-in hybrids as a potential “flexibility” option to include in the regulation.

One independent energy economics specialist, who was not involved with the study, called the report a “very useful addition” after a long period in which segments of the automotive sector argued there was too little data to accurately evaluate real-world emissions.

“These findings show, beyond any doubt, that the difference in lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional cars,” they said. “All regulatory changes regarding PHEVs should be implemented with utmost care and in the light of that evidence.”