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Plug-in hybrid electric vehicles emit almost 5x greater planet-heating emissions than official figures indicate, according to a recent analysis.

Widening Gap Between Official and Actual Emissions

Data shows that PHEVs release just 19% less CO₂ than traditional petrol and diesel cars, based on research conducted by a advocacy organization. That differs sharply with laboratory estimates, which assumed a 75% reduction in pollution.

Analysts examined data from in-vehicle fuel consumption meters of eight hundred thousand cars registered in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Real-world emissions are rising, while official figures are falling,” said a lead researcher participating in the study. “This gap is growing and poses a serious problem. As a result, PHEVs emit nearly as heavily as gasoline vehicles.”

Primary Factors Behind the Emissions Gap

Analysts linked most of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in battery mode compared to overall mileage. The team found that only a quarter of travel was completed in EV mode, while lab estimates suggested 84%.

Even, when running in electric mode, pollution levels were significantly higher than official projections. That occurred because EV motors were insufficiently powerful enough to operate alone, leading to combustion motors burning fossil fuels for almost a third of the travel completed in electric mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV emissions enabled four major carmaker companies to escape more than €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs would spend approximately €500 more annually in operating costs than is assumed under lab conditions.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are obviously far from the truth,” stated a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and saving money. Actually, PHEVs are only slightly better than standard gas and diesel cars in terms of fuel use, CO₂ production, and operating expenses.”

Policy Debate and Automotive Lobbying

Plug-in hybrid cars have lately been drawn again into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and resistance from member states with significant car industries.

Some senior officials have suggested PHEVs as a possible “compromise” option to include in the legislation.

One independent energy policy expert, who was not involved with the research, called the report a “highly valuable addition” after a long period in which parts of the car sector argued there was too little information to properly assess actual CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV fuel consumption and CO₂ output is significantly larger than for gasoline or conventional vehicles,” the expert said. “Any policy adjustments concerning PHEVs should be implemented with utmost care and considering this evidence.”