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Plug-in hybrid electric vehicles emit almost five times more global warming emissions than lab-reported data indicate, according to a recent analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Data reveals that PHEVs release just 19% less CO₂ than traditional petrol and diesel vehicles, based on research carried out by a advocacy group. This differs significantly with lab tests, which suggested a three-quarters decrease in pollution.

Researchers examined information from onboard energy use monitors of eight hundred thousand cars sold in Europe between 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 three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” stated a senior analyst involved in the report. “That discrepancy is widening and creates a significant issue. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Analysts attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in electric power relative to total distance. The team determined that just a quarter of driving was completed in electric mode, while official assumptions suggested over four-fifths.

Additionally, when operating in EV mode, emission amounts were significantly higher than official estimates. That occurred because electric motors were not strong enough to function independently, leading to combustion motors burning fossil fuels for almost one-third of the travel completed in electric mode.

Regulatory and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled several major carmaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially easing adherence with European Union average fleet CO₂ standards.

Furthermore, owners of PHEVs would pay approximately €500 extra annually in operating costs than would be assumed under laboratory tests.

“The bold statements that manufacturers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are little improved than standard gas and diesel cars in terms of fuel consumption, CO₂ production, and running costs.”

Policy Discussion and Industry Pressure

Hybrid vehicles have lately been brought back into policy debates as carmakers have pressed the European Union to relax CO₂ targets. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense pressure from the car industry and resistance from EU countries with large car industries.

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

An independent energy economics expert, who was unaffiliated with the study, called the report a “very useful contribution” after a long period in which segments of the car sector claimed there was insufficient information to accurately assess real-world CO2 output.

“The results show, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or diesel vehicles,” they stated. “Any policy changes concerning PHEVs should be made with utmost caution and in the light of that data.”