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Plug-in hybrid cars produce nearly five times greater global warming pollution than lab-reported data indicate, according to a recent report.

Growing Gap Between Official and Real-World Emissions

Data reveals that PHEVs release just one-fifth less CO₂ than conventional petrol and diesel cars, according to research conducted by a advocacy group. That contrasts sharply with lab estimates, which assumed a three-quarters decrease in pollution.

Analysts studied information from in-vehicle energy use monitors of 800,000 cars registered in the EU from 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Real-world emissions are rising, while official emissions are falling,” stated a lead analyst involved in the report. “That gap is growing and creates a serious problem. As a result, PHEVs emit almost as much as petrol cars.”

Key Reasons Driving the Discrepancy

Researchers linked most of the difference to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric mode relative to total mileage. They found that only a quarter of driving was completed in electric mode, whereas official estimates assumed over four-fifths.

Even, when operating in electric mode, pollution levels were well above lab projections. That occurred because electric motors were insufficiently powerful enough to operate alone, resulting to engines burning fossil fuels for nearly a third of the travel completed in EV mode.

Policy and Financial Implications

According to calculations, the lowballing of PHEV emissions enabled several major carmaker groups to avoid more than €5bn in fines from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 extra annually in operating expenses than would be estimated under lab tests.

“The bold claims that automakers often promote about their plug-in hybrid vehicles are obviously way off the mark,” commented a automotive analyst. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are only slightly improved than regular petrol and diesel cars in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have recently been drawn again into policy discussions as carmakers have pressed the EU to relax CO₂ targets. A planned ban on new combustion engine cars in 2035 has faced intense pressure from the automotive industry and resistance from member states with significant automotive manufacturing.

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

An external energy policy specialist, who was not involved with the study, called the analysis a “very useful addition” after a long period in which segments of the car industry argued there was insufficient information to accurately evaluate real-world emissions.

“These findings demonstrate, beyond any doubt, that the gap between lab and actual PHEV fuel consumption and CO₂ output is significantly greater than for gasoline or diesel cars,” they stated. “All regulatory adjustments regarding PHEVs should be made with utmost caution and in the light of that evidence.”