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Plug-in hybrid cars produce almost 5x greater global warming pollution than lab-reported data show, as per a new report.

Widening Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs emit only one-fifth less CO₂ than traditional gas and diesel cars, based on analysis conducted by a non-profit organization. That contrasts significantly with lab estimates, which assumed a three-quarters decrease in pollution.

Researchers examined information from onboard fuel consumption meters of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while lab-reported figures are falling,” said a senior researcher participating in the report. “That gap is growing and creates a significant issue. Consequently, PHEVs pollute nearly as heavily as petrol cars.”

Key Reasons Driving the Emissions Gap

Analysts linked the majority of the gap to overestimates of the “electric driving share” – the percentage of miles driven in electric mode compared to total mileage. They found that just a quarter of driving was completed in electric mode, while lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution levels were well above lab estimates. This happened because EV motors were insufficiently powerful sufficient to function independently, resulting to engines using fossil fuels for nearly a third of the travel covered in electric mode.

Regulatory and Financial Consequences

According to calculations, the underestimation of PHEV emissions allowed four major carmaker companies to avoid over €5bn in penalties from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs could pay approximately €500 extra annually in running costs than would be assumed under laboratory conditions.

“The strong statements that automakers like to make about their plug-in hybrid vehicles are clearly way off the mark,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly improved than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid cars have recently been drawn back into policy debates as automakers have lobbied the EU to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion vehicles in 2035 has faced intense pressure from the automotive industry and opposition from EU countries with significant car manufacturing.

Some high-level officials have proposed PHEVs as a possible “flexibility” solution to include in the legislation.

An independent energy economics expert, who was not involved with the research, called the report a “very useful addition” after years in which segments of the car industry claimed there was insufficient data to properly evaluate actual emissions.

“These findings demonstrate, without question, that the gap between lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for petrol or conventional cars,” they said. “Any regulatory adjustments concerning PHEVs should be made with utmost caution and considering this evidence.”