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Plug-in hybrid electric vehicles emit nearly 5x greater planet-heating emissions than official figures show, as per a new analysis.

Widening Discrepancy In Lab and Actual CO2 Output

Data reveals that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel cars, based on research carried out by a advocacy group. That contrasts sharply with lab estimates, which assumed a 75% reduction in emissions.

Analysts studied information from in-vehicle energy use monitors of eight hundred thousand cars registered in the EU from 2021 and 2023. They discovered that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official emissions are falling,” said a lead researcher participating in the report. “That discrepancy is widening and poses a significant problem. As a result, PHEVs emit nearly as much as gasoline cars.”

Primary Factors Behind the Discrepancy

Analysts attributed the majority of the gap to inflated estimates of the “electric driving share” – the ratio of miles travelled in electric mode compared to total mileage. They found that only a quarter of travel was completed in EV mode, whereas official assumptions assumed 84%.

Additionally, when operating in EV mode, emission levels were well above official estimates. This occurred because electric motors were insufficiently powerful sufficient to function independently, resulting to combustion motors using gasoline for almost a third of the travel completed in EV mode.

Policy and Financial Implications

Based on estimates, the lowballing of PHEV emissions enabled several major automaker companies to escape more than €5bn in penalties between 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ targets.

Additionally, owners of PHEVs could pay about €500 more annually in running costs than would be assumed under laboratory tests.

“The bold statements that automakers like to make about their PHEV cars are obviously far from the truth,” commented a automotive analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little better than regular gas and diesel vehicles in terms of energy use, CO₂ production, and running expenses.”

Political Debate and Automotive Pressure

Plug-in hybrid vehicles have recently been brought again into political discussions as automakers have lobbied the EU to weaken CO₂ targets. A proposed prohibition on new combustion engine vehicles in 2035 has faced heavy lobbying from the automotive industry and opposition from member states with significant car manufacturing.

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

An independent energy economics specialist, who was not involved with the study, described the report a “very useful addition” after a long period in which parts of the car industry argued there was too little data to accurately evaluate real-world emissions.

“These findings demonstrate, without question, that the gap between lab and real-world PHEV energy use and CO₂ output is much, much greater than for petrol or diesel vehicles,” the expert said. “All policy changes concerning PHEVs should be made with utmost care and considering this evidence.”