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Plug-in hybrid electric vehicles produce nearly 5x greater global warming emissions than lab-reported data indicate, according to a recent report.

Widening Gap Between Lab and Real-World Emissions

Statistics shows that PHEVs release just 19% less CO₂ than traditional petrol and diesel cars, based on analysis conducted by a non-profit group. That contrasts significantly with laboratory estimates, which assumed a three-quarters decrease in emissions.

Researchers examined information from in-vehicle fuel consumption meters of 800,000 vehicles sold in the EU from 2021 and 2023. They discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab figures, up from three and a half times in 2021.

“Actual emissions are rising, while official emissions are decreasing,” stated a senior researcher participating in the study. “That gap is widening and creates a serious issue. As a result, PHEVs emit almost as heavily as petrol cars.”

Key Reasons Behind the Emissions Gap

Analysts linked the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers travelled in battery mode relative to total mileage. They found that just a quarter of travel was completed in EV mode, while official assumptions assumed 84%.

Even, when running in EV mode, pollution levels were significantly higher than official projections. This occurred because electric motors were insufficiently powerful enough to function independently, resulting to engines using fossil fuels for almost a third of the travel covered in EV mode.

Policy and Financial Consequences

Based on calculations, the lowballing of PHEV emissions enabled four large carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially easing adherence with European Union fleet-average CO₂ standards.

Additionally, owners of PHEVs would pay approximately €500 extra per year in operating expenses than is estimated under lab tests.

“The bold statements that manufacturers like to make about their PHEV cars are obviously way off the mark,” commented a automotive analyst. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and saving money. In reality, PHEVs are only slightly improved than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Pressure

Hybrid vehicles have recently been brought again into policy debates as automakers have pressed the EU to relax CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced heavy pressure from the car industry and opposition from member states with significant automotive industries.

Several high-level politicians have suggested PHEVs as a potential “flexibility” option to include in the legislation.

An independent energy policy expert, who was not involved with the study, called the report a “highly valuable addition” after a long period in which segments of the car industry claimed there was too little information to accurately assess real-world emissions.

“These findings show, beyond any doubt, that the difference in official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional cars,” they stated. “Any regulatory adjustments concerning PHEVs should be implemented with utmost care and in the light of this data.”