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

Widening Gap Between Lab and Real-World Emissions

Statistics reveals that PHEVs release just one-fifth lower CO₂ than traditional gas and diesel cars, based on research conducted by a advocacy group. This contrasts significantly with laboratory estimates, which assumed a 75% reduction in pollution.

Analysts studied data from onboard energy use meters of 800,000 cars sold in the EU between 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were 4.9 times higher than official estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” stated a lead researcher involved in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs emit almost as much as petrol vehicles.”

Primary Reasons Driving the Emissions Gap

Analysts linked the majority of the gap to inflated estimates of the “utility factor” – the ratio of miles driven in electric power relative to total distance. The team determined that only 27% of driving was done in electric mode, whereas lab assumptions assumed 84%.

Additionally, when operating in electric mode, pollution levels were significantly higher than lab estimates. This happened because EV motors were not strong enough to operate alone, leading to combustion motors using gasoline for almost a third of the distance covered in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV CO2 output allowed four large automaker companies to avoid more than €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with EU average fleet CO₂ targets.

Additionally, owners of PHEVs could spend approximately €500 extra per year in running expenses than is assumed under laboratory tests.

“The strong statements that automakers like to make about their PHEV vehicles are clearly way off the mark,” commented a transport expert. “Buyers are being duped into believing that by purchasing a PHEV, they are helping the environment and cutting money. In reality, PHEVs are only slightly improved than standard petrol and diesel cars in terms of fuel consumption, CO₂ production, and operating costs.”

Policy Debate and Automotive Pressure

Plug-in hybrid cars have lately been brought again into policy discussions as automakers have pressed the EU to weaken CO₂ standards. A proposed prohibition on sales of new combustion engine cars in 2035 has faced heavy lobbying from the car industry and resistance from EU countries with significant car industries.

Some senior politicians have suggested PHEVs as a potential “flexibility” option to introduce in the legislation.

An independent energy economics specialist, who was not involved with the research, described the analysis a “very useful contribution” after years in which segments of the automotive sector claimed there was insufficient data to properly evaluate real-world CO2 output.

“These findings show, without question, that the gap in official and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or diesel cars,” the expert said. “All regulatory changes regarding PHEVs should be implemented with utmost caution and in the light of that evidence.”