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Plug-in hybrid cars emit almost 5x more planet-heating emissions than official figures indicate, as per a new report.

Widening Discrepancy Between Official and Actual Emissions

Data shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit group. This differs significantly with laboratory tests, which assumed a 75% decrease in emissions.

Researchers examined data from in-vehicle fuel consumption monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, up from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a lead analyst involved in the report. “This discrepancy is widening and poses a significant issue. As a result, PHEVs pollute nearly as much as petrol cars.”

Key Reasons Behind the Emissions Gap

Researchers linked most of the gap to overestimates of the “utility factor” – the ratio of kilometers driven in electric power compared to total mileage. They determined that just a quarter of driving was completed in electric mode, whereas official estimates assumed 84%.

Additionally, when running in EV mode, pollution amounts were well above lab estimates. This occurred because EV motors were insufficiently powerful sufficient to function alone, leading to engines using fossil fuels for almost a third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on calculations, the underestimation of PHEV emissions allowed several large carmaker companies to avoid more than €5bn in fines between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ standards.

Furthermore, drivers of PHEVs would pay about €500 extra annually in operating expenses than would be estimated under lab conditions.

“The bold statements that automakers often promote about their PHEV vehicles are clearly far from the mark,” commented a transport analyst. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the environment and cutting costs. In reality, PHEVs are little better than standard gas and diesel vehicles 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 discussions as carmakers have pressed the European Union to weaken CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced intense pressure from the car industry and resistance from member states with significant automotive manufacturing.

Some high-level politicians have proposed plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

An independent energy economics expert, who was not involved with the research, called the report a “highly valuable addition” after years in which parts of the automotive sector argued there was insufficient data to accurately assess real-world CO2 output.

“These findings show, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ emissions is much, much larger than for gasoline or diesel cars,” they said. “Any policy changes concerning PHEVs should be made with utmost caution and in the light of this data.”