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Plug-in hybrid electric vehicles release nearly five times greater planet-heating pollution than official figures indicate, according to a new report.

Widening Gap Between Lab and Actual Emissions

Statistics shows that PHEVs emit just 19% lower CO₂ than conventional petrol and diesel vehicles, based on analysis conducted by a non-profit group. This differs sharply with lab estimates, which suggested a three-quarters reduction in emissions.

Researchers examined information from in-vehicle energy use meters of 800,000 vehicles registered in Europe between 2021 and 2023. They discovered that real-world CO₂ output from PHEVs in 2023 were nearly five times higher than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are decreasing,” stated a lead researcher involved in the report. “This discrepancy is widening and creates a serious issue. As a result, PHEVs pollute nearly as heavily as petrol vehicles.”

Key Reasons Behind the Emissions Gap

Analysts linked the majority of the difference to inflated estimates of the “utility factor” – the percentage of kilometers travelled in battery mode relative to total distance. The team found that only 27% of travel was completed in EV mode, while lab estimates suggested 84%.

Even, when operating in electric mode, pollution amounts were significantly higher than lab projections. That happened because EV motors were insufficiently powerful enough to function independently, leading to combustion motors burning fossil fuels for almost one-third of the distance covered in EV mode.

Regulatory and Financial Consequences

Based on estimates, the lowballing of PHEV CO2 output enabled four major automaker companies to escape over €5bn in fines between 2021 and 2023, by falsely simplifying adherence with EU fleet-average CO₂ targets.

Additionally, owners of PHEVs would pay approximately €500 extra per year in running costs than is assumed under laboratory conditions.

“The strong claims that automakers often promote about their plug-in hybrid cars are clearly way off the mark,” stated a transport analyst. “Buyers are being duped into thinking that by purchasing a PHEV, they are helping the planet and cutting costs. Actually, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of fuel use, CO₂ emissions, and running costs.”

Policy Debate and Industry Lobbying

Hybrid vehicles have lately been brought back into policy discussions as carmakers have lobbied the EU to weaken CO₂ standards. A planned ban on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car industry and resistance from EU countries with significant car manufacturing.

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

An external energy policy specialist, who was unaffiliated with the study, described the report a “very useful contribution” after years in which parts of the automotive industry claimed there was insufficient data to properly evaluate real-world emissions.

“The results show, without question, that the difference in official and actual PHEV energy use and CO₂ emissions is much, much greater than for petrol or diesel vehicles,” they stated. “Any policy adjustments regarding PHEVs should be made with utmost care and considering that data.”