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Plug-in hybrid electric vehicles release almost five times greater global warming emissions than lab-reported data indicate, as per a recent report.

Widening Gap Between Lab and Real-World Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than traditional gas and diesel vehicles, according to analysis carried out by a non-profit group. That differs significantly with laboratory estimates, which assumed a 75% decrease in pollution.

Analysts examined data from onboard fuel consumption monitors of eight hundred thousand cars registered in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than lab estimates, increased from 3.5 times in 2021.

“Actual CO2 output are increasing, while official emissions are decreasing,” stated a lead analyst participating in the study. “This gap is growing and creates a significant issue. As a result, PHEVs pollute almost as heavily as petrol cars.”

Key Reasons Behind the Emissions Gap

Analysts linked most of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in battery mode relative to overall mileage. The team determined that just 27% of driving was completed in EV mode, whereas official estimates suggested 84%.

Additionally, when operating in EV mode, emission levels were well above lab projections. That happened because EV motors were not strong enough to operate independently, leading to combustion motors burning gasoline for almost one-third of the distance completed in electric mode.

Policy and Financial Consequences

Based on estimates, the underestimation of PHEV CO2 output enabled several major automaker companies to avoid more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would spend approximately €500 extra annually in running expenses than would be assumed under laboratory tests.

“The bold statements that automakers like to make about their plug-in hybrid cars are obviously way off the truth,” stated a automotive expert. “Buyers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running costs.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have lately been drawn back into policy debates as automakers have pressed the European Union to weaken CO₂ standards. A planned ban on new combustion engine cars in 2035 has faced heavy pressure from the automotive sector and opposition from EU countries with significant car industries.

Some high-level politicians have suggested PHEVs as a possible “compromise” solution to introduce in the regulation.

An external energy economics expert, who was unaffiliated with the research, called the analysis a “very useful contribution” after years in which segments of the car industry argued there was insufficient information to accurately evaluate actual CO2 output.

“The results demonstrate, beyond any doubt, that the gap in lab and actual PHEV energy use and CO₂ emissions is significantly larger than for petrol or conventional vehicles,” they said. “Any policy changes concerning PHEVs should be made with utmost care and considering that data.”