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Plug-in hybrid cars produce almost five times more planet-heating emissions than lab-reported figures indicate, as per a new analysis.

Growing Discrepancy Between Lab and Real-World Emissions

Data reveals that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a advocacy group. That contrasts sharply with laboratory estimates, which assumed a three-quarters reduction in emissions.

Researchers studied data from in-vehicle fuel consumption meters of eight hundred thousand cars registered in the EU from 2021 and 2023. The team found that real-world CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Real-world emissions are increasing, while lab-reported figures are falling,” said a lead analyst participating in the report. “That gap is widening and poses a significant problem. As a result, PHEVs pollute nearly as heavily as gasoline vehicles.”

Primary Reasons Driving the Emissions Gap

Researchers attributed the majority of the gap to inflated estimates of the “utility factor” – the percentage of miles driven in battery mode compared to total mileage. The team found that only a quarter of driving was done in EV mode, while lab assumptions assumed over four-fifths.

Even, when running in EV mode, pollution amounts were significantly higher than lab estimates. That happened because EV motors were not strong enough to function alone, resulting to combustion motors using fossil fuels for almost one-third of the travel completed in electric mode.

Policy and Economic Consequences

According to calculations, the underestimation of PHEV CO2 output allowed four large automaker companies to avoid over €5bn in penalties from 2021 and 2023, by falsely simplifying adherence with EU average fleet CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 more annually in operating costs than is estimated under laboratory conditions.

“The strong statements that automakers like to make about their PHEV cars are obviously far from the mark,” stated a transport analyst. “Buyers are being misled into believing that by buying a PHEV, they are benefiting the planet and saving costs. Actually, PHEVs are only slightly improved than standard gas and diesel cars in terms of fuel use, CO₂ emissions, and operating expenses.”

Political Debate and Industry Lobbying

Plug-in hybrid vehicles have lately been brought again into political debates as carmakers have pressed the European Union to weaken CO₂ standards. A planned ban on new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and resistance from member states with large car industries.

Some senior politicians have suggested plug-in hybrids as a potential “compromise” solution to introduce in the regulation.

An independent energy economics expert, who was unaffiliated with the research, called the analysis a “very useful contribution” after a long period in which parts of the car sector argued there was insufficient data to properly assess real-world CO2 output.

“The results show, beyond any doubt, that the gap between lab and real-world PHEV fuel consumption and CO₂ output is significantly larger than for petrol or diesel cars,” the expert stated. “All policy changes concerning PHEVs should be made with extreme caution and in the light of that data.”