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Plug-in hybrid cars release nearly 5x greater planet-heating emissions than official figures indicate, according to a recent analysis.

Growing Discrepancy Between Lab and Actual Emissions

Statistics reveals that PHEVs emit just 19% lower CO₂ than traditional petrol and diesel cars, based on analysis carried out by a non-profit organization. That contrasts significantly with lab tests, which assumed a three-quarters decrease in pollution.

Analysts examined data from onboard energy use meters of 800,000 vehicles registered in Europe between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official figures, up from 3.5 times in 2021.

“Actual emissions are increasing, while official figures are decreasing,” said a lead researcher participating in the study. “This gap is growing and creates a serious problem. As a result, PHEVs emit nearly as heavily as petrol cars.”

Primary Reasons Behind the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “electric driving share” – the percentage of kilometers driven in battery mode relative to total distance. The team determined that only 27% of driving was done in electric mode, whereas official assumptions suggested 84%.

Additionally, when running in EV mode, emission amounts were well above lab estimates. That occurred because EV motors were not strong enough to function independently, leading to engines using gasoline for almost one-third of the distance covered in electric mode.

Policy and Financial Consequences

According to calculations, the underestimation of PHEV emissions allowed several large carmaker groups to escape over €5bn in fines between 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs could spend about €500 more annually in operating costs than is assumed under lab conditions.

“The strong claims that automakers like to make about their PHEV cars are clearly way off the truth,” commented a transport expert. “Consumers are being misled into believing that by buying a PHEV, they are helping the environment and cutting money. In reality, PHEVs are little better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid vehicles have lately been brought again into policy discussions as automakers have lobbied the EU to relax CO₂ targets. A planned ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive industry and resistance from member states with large car manufacturing.

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

An external energy policy expert, who was unaffiliated with the research, described the report a “highly valuable addition” after a long period in which segments of the automotive sector claimed there was insufficient data to accurately assess real-world CO2 output.

“The results demonstrate, without question, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for petrol or diesel cars,” the expert stated. “All regulatory changes regarding PHEVs should be made with utmost caution and in the light of this data.”