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Plug-in hybrid cars emit nearly five times more global warming pollution than official figures show, according to a recent report.

Growing Discrepancy In Official and Actual CO2 Output

Data shows that PHEVs release only one-fifth lower CO₂ than traditional gas and diesel cars, based on analysis carried out by a non-profit organization. That contrasts significantly with laboratory tests, which suggested a 75% reduction in pollution.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 vehicles registered in the EU from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab figures, increased from 3.5 times in 2021.

“Actual emissions are increasing, while lab-reported emissions are falling,” stated a lead researcher participating in the study. “That discrepancy is widening and creates a serious problem. As a result, PHEVs emit nearly as heavily as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Researchers attributed most of the gap to inflated estimates of the “utility factor” – the percentage of kilometers driven in battery power relative to overall mileage. The team determined that just a quarter of driving was completed in electric mode, whereas lab estimates suggested over four-fifths.

Even, when operating in electric mode, pollution levels were well above lab estimates. That occurred because EV motors were not strong sufficient to operate independently, resulting to combustion motors burning gasoline for almost a third of the distance covered in EV mode.

Policy and Financial Consequences

According to estimates, the underestimation of PHEV CO2 output enabled four major automaker companies to avoid over €5bn in fines between 2021 and 2023, by artificially easing compliance with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 extra annually in running costs than would be estimated under laboratory tests.

“The strong claims that manufacturers often promote about their plug-in hybrid vehicles are clearly way off the truth,” commented a transport analyst. “Consumers are being misled into believing that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are little better than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have recently been brought again into political debates as automakers have lobbied the European Union to weaken CO₂ targets. A planned prohibition on new internal combustion vehicles in 2035 has faced heavy lobbying from the automotive sector and opposition from member states with large automotive industries.

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

An external energy economics expert, who was unaffiliated with the research, described the report a “highly valuable addition” after a long period in which parts of the automotive industry claimed there was insufficient data to properly evaluate actual emissions.

“These findings demonstrate, without question, that the difference between official and real-world PHEV fuel consumption and CO₂ emissions is significantly greater than for gasoline or diesel cars,” the expert said. “All policy adjustments regarding PHEVs should be made with extreme caution and in the light of this data.”