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Plug-in hybrid cars produce nearly 5x greater global warming pollution than official figures indicate, according to a recent analysis.

Widening Discrepancy Between Official and Real-World Emissions

Data reveals that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to research conducted by a non-profit group. That differs sharply with laboratory tests, which assumed a three-quarters decrease in emissions.

Researchers studied information from in-vehicle fuel consumption monitors of 800,000 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, up from 3.5 times in 2021.

“Real-world emissions are rising, while lab-reported emissions are falling,” stated a senior analyst involved in the study. “This discrepancy is widening and poses a significant problem. As a result, PHEVs pollute nearly as heavily as gasoline cars.”

Key Reasons Behind the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “utility factor” – the ratio of kilometers driven in electric power compared to overall distance. They found that just a quarter of driving was completed in EV mode, while official estimates suggested 84%.

Additionally, when operating in EV mode, pollution levels were well above official estimates. That happened because electric motors were not strong enough to operate independently, leading to engines burning fossil fuels for almost one-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 penalties between 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 more per year in running expenses than would be assumed under lab tests.

“The strong claims that manufacturers often promote about their plug-in hybrid cars are clearly way off the mark,” stated a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and cutting money. Actually, PHEVs are little better than regular gas and diesel cars in terms of fuel consumption, CO₂ production, and operating expenses.”

Policy Discussion and Industry Lobbying

Hybrid vehicles have recently been drawn again into policy debates as carmakers have lobbied the European Union to relax CO₂ standards. A proposed ban on new combustion engine vehicles in 2035 has faced intense pressure from the car industry and resistance from member states with significant car industries.

Several senior politicians have proposed PHEVs as a possible “flexibility” solution to introduce in the legislation.

One external energy economics specialist, who was unaffiliated with the study, called the report a “very useful addition” after a long period in which segments of the car industry claimed there was too little information to properly evaluate actual CO2 output.

“These findings demonstrate, without question, that the gap in official and actual PHEV fuel consumption and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert stated. “Any regulatory changes regarding PHEVs should be implemented with utmost care and considering this data.”