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Plug-in hybrid cars produce almost 5x greater global warming emissions than official data show, according to a recent analysis.

Growing Gap In Lab and Actual CO2 Output

Statistics shows that PHEVs emit just 19% less CO₂ than conventional petrol and diesel cars, based on research conducted by a non-profit organization. This contrasts significantly with lab estimates, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle energy use meters of 800,000 vehicles registered in the EU between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times greater than official estimates, up from three and a half times in 2021.

“Real-world emissions are increasing, while official emissions are falling,” said a senior analyst participating in the study. “That gap is growing and creates a significant problem. As a result, PHEVs emit almost as much as gasoline vehicles.”

Primary Factors Driving the Emissions Gap

Analysts attributed the majority of the difference to overestimates of the “electric driving share” – the ratio of kilometers driven in battery power relative to overall mileage. They found that only 27% of travel was completed in electric mode, while lab estimates suggested 84%.

Additionally, when operating in EV mode, emission amounts were significantly higher than lab estimates. This occurred because EV motors were not strong sufficient to function alone, leading to combustion motors using fossil fuels for almost one-third of the distance completed in EV mode.

Policy and Economic Implications

According to calculations, the lowballing of PHEV CO2 output allowed several major automaker groups to avoid over €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union average fleet CO₂ standards.

Additionally, drivers of PHEVs could spend approximately €500 more per year in operating costs than is assumed under laboratory conditions.

“The strong statements that manufacturers like to make about their PHEV vehicles are obviously far from the truth,” commented a automotive analyst. “Consumers are being duped into thinking that by purchasing a PHEV, they are helping the planet and saving costs. Actually, PHEVs are only slightly improved than regular gas and diesel cars in terms of energy consumption, CO₂ production, and operating expenses.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been brought back into policy debates as carmakers have pressed the European Union to weaken CO₂ standards. A proposed ban on new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and opposition from EU countries with large car manufacturing.

Some senior politicians have suggested plug-in hybrids as a potential “flexibility” option to introduce in the legislation.

An independent energy policy expert, who was not involved with the research, called the analysis a “very useful contribution” after years in which parts of the automotive industry claimed there was insufficient data to properly evaluate real-world emissions.

“These findings demonstrate, without question, that the gap between official and real-world PHEV fuel consumption and CO₂ emissions is significantly larger than for gasoline or conventional cars,” they said. “All regulatory changes regarding PHEVs should be made with utmost caution and considering that data.”