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Plug-in hybrid cars produce nearly 5x greater planet-heating pollution than lab-reported data indicate, as per a recent report.

Growing Discrepancy Between Lab and Real-World CO2 Output

Data reveals that PHEVs release only one-fifth less CO₂ than traditional petrol and diesel vehicles, according to research conducted by a non-profit group. That differs sharply with lab tests, which suggested a 75% reduction in pollution.

Researchers examined information from in-vehicle fuel consumption monitors of eight hundred thousand vehicles sold in Europe from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual CO2 output are increasing, while official figures are falling,” said a lead analyst participating in the study. “That gap is growing and poses a significant problem. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Primary Reasons Driving the Emissions Gap

Researchers attributed the majority of the difference to inflated estimates of the “utility factor” – the percentage of miles travelled in battery power relative to total mileage. They determined that only a quarter of driving was done in electric mode, while lab assumptions assumed over four-fifths.

Additionally, when running in EV mode, emission amounts were significantly higher than lab estimates. This happened because electric motors were insufficiently powerful sufficient to operate alone, leading to combustion motors using gasoline for nearly a third of the distance completed in electric mode.

Regulatory and Financial Implications

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

Furthermore, owners of PHEVs would pay approximately €500 more per year in running expenses than would be estimated under lab tests.

“The bold statements that automakers often promote about their PHEV vehicles are obviously way off the truth,” commented a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy use, CO₂ production, and running costs.”

Policy Discussion and Industry Lobbying

Plug-in 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 vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with significant automotive manufacturing.

Some high-level politicians have proposed PHEVs as a potential “flexibility” solution to include in the regulation.

An external energy policy specialist, who was unaffiliated with the research, described the analysis a “highly valuable contribution” after a long period in which parts of the car sector claimed there was too little data to properly evaluate actual CO2 output.

“These findings show, beyond any doubt, that the difference between lab and real-world PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or conventional vehicles,” they said. “Any regulatory changes regarding PHEVs should be implemented with extreme care and considering that data.”