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Plug-in hybrid cars produce almost 5x more global warming pollution than official figures show, according to a recent analysis.

Growing Discrepancy In Official and Real-World Emissions

Data shows that PHEVs release only one-fifth less CO₂ than conventional petrol and diesel cars, based on research conducted by a advocacy organization. This differs significantly with laboratory estimates, which suggested a three-quarters reduction in pollution.

Analysts examined information from onboard fuel consumption monitors of eight hundred thousand vehicles sold in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” said a lead researcher participating in the study. “That gap is widening and creates a serious issue. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Driving the Discrepancy

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of miles driven in electric mode compared to total distance. The team determined that only 27% of travel was done in electric mode, while official assumptions assumed over four-fifths.

Even, when running in electric mode, emission levels were significantly higher than lab estimates. That occurred because EV motors were insufficiently powerful sufficient to function independently, resulting to combustion motors burning fossil fuels for almost a third of the travel completed in electric mode.

Regulatory and Economic Consequences

Based on estimates, the underestimation of PHEV CO2 output allowed four major carmaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially easing adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs would spend about €500 more annually in running expenses than is estimated under laboratory tests.

“The bold statements that automakers often promote about their plug-in hybrid cars are clearly far from the truth,” commented a transport analyst. “Consumers are being duped into thinking that by buying a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly improved than regular gas and diesel vehicles in terms of energy use, CO₂ emissions, and operating expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been brought back into political debates as automakers have lobbied the European Union to relax CO₂ targets. A proposed ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with significant car manufacturing.

Some high-level officials have suggested PHEVs as a possible “flexibility” option to include in the regulation.

An external energy policy expert, who was not involved with the study, called the report a “highly valuable addition” after a long period in which parts of the car industry argued there was too little information to properly evaluate actual CO2 output.

“These findings demonstrate, without question, that the gap in official and actual PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel cars,” they said. “All regulatory adjustments regarding PHEVs should be made with extreme caution and considering this data.”