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Plug-in hybrid cars emit almost five times more planet-heating pollution than official data show, according to a new report.

Widening Discrepancy Between Lab and Real-World Emissions

Statistics reveals that PHEVs emit only 19% lower CO₂ than conventional petrol and diesel vehicles, based on analysis carried out by a advocacy group. That differs sharply with lab estimates, which suggested a 75% reduction in emissions.

Analysts examined information from in-vehicle fuel consumption meters of eight hundred thousand cars registered in the EU from 2021 and 2023. They discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times greater than official estimates, increased from 3.5 times in 2021.

“Actual emissions are rising, while lab-reported emissions are falling,” said a lead analyst involved in the report. “This gap is widening and creates a significant problem. As a result, PHEVs pollute nearly as heavily as petrol cars.”

Key Reasons Driving the Emissions Gap

Researchers attributed most of the gap to overestimates of the “utility factor” – the percentage of kilometers driven in electric mode relative to total distance. They determined that only a quarter of travel was done in EV mode, while lab assumptions suggested over four-fifths.

Even, when operating in electric mode, pollution amounts were significantly higher than lab projections. This happened because EV motors were not strong sufficient to function alone, resulting to combustion motors using fossil fuels for almost a third of the distance completed in EV mode.

Policy and Economic Implications

Based on calculations, the lowballing of PHEV CO2 output enabled four major automaker groups to escape over €5bn in fines from 2021 and 2023, by falsely easing compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs would spend approximately €500 extra per year in operating costs than would be estimated under laboratory conditions.

“The bold claims that manufacturers often promote about their PHEV cars are obviously way off the truth,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and cutting costs. In reality, PHEVs are little better than standard gas and diesel vehicles in terms of energy consumption, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Lobbying

Hybrid cars have lately been brought again into political discussions as carmakers have lobbied the EU to weaken CO₂ targets. A proposed ban on sales of new combustion engine cars in 2035 has faced intense pressure from the car industry and opposition from member states with significant car manufacturing.

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

An independent energy economics expert, who was not involved with the research, described the analysis a “highly valuable contribution” after years in which segments of the car sector argued there was too little data to accurately assess real-world CO2 output.

“The results show, without question, that the difference between lab and actual PHEV energy use and CO₂ output is significantly larger than for petrol or conventional vehicles,” they stated. “All regulatory adjustments regarding PHEVs should be made with utmost care and in the light of that data.”