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Plug-in hybrid cars emit nearly five times more global warming emissions than lab-reported data show, according to a new analysis.

Widening Discrepancy Between Official and Real-World CO2 Output

Statistics shows that PHEVs release just one-fifth lower CO₂ than traditional petrol and diesel vehicles, according to analysis carried out by a non-profit group. That contrasts significantly with laboratory tests, which assumed a 75% reduction in emissions.

Researchers studied data from onboard energy use meters of 800,000 cars registered in the EU from 2021 and 2023. They found that actual CO₂ output from PHEVs in 2023 were nearly five times higher than lab estimates, up from 3.5 times in 2021.

“Real-world CO2 output are increasing, while official figures are falling,” stated a lead researcher participating in the study. “This discrepancy is growing and poses a significant issue. Consequently, PHEVs emit nearly as much as gasoline vehicles.”

Primary Factors Driving the Discrepancy

Analysts linked most of the gap to overestimates of the “utility factor” – the percentage of kilometers travelled in electric power compared to total distance. The team determined that just 27% of travel was completed in EV mode, while official estimates suggested 84%.

Additionally, when operating in electric mode, pollution amounts were significantly higher than lab estimates. This happened because EV motors were insufficiently powerful sufficient to function alone, resulting to combustion motors using gasoline for almost one-third of the travel completed in electric mode.

Policy and Economic Implications

Based on estimates, the lowballing of PHEV emissions allowed four large carmaker companies to avoid over €5bn in fines from 2021 and 2023, by falsely easing compliance with EU average fleet CO₂ standards.

Additionally, drivers of PHEVs could pay approximately €500 more per year in operating expenses than is estimated under laboratory tests.

“The bold claims that automakers often promote about their PHEV vehicles are obviously far from the mark,” stated a automotive expert. “Consumers are being duped into believing that by purchasing a PHEV, they are benefiting the planet and saving money. In reality, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy consumption, CO₂ emissions, and running expenses.”

Political Debate and Industry Pressure

Plug-in hybrid vehicles have lately been drawn again into political discussions as automakers have lobbied the EU to weaken CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced heavy lobbying from the car sector and opposition from member states with large car industries.

Several high-level politicians have suggested plug-in hybrids as a potential “flexibility” solution to introduce in the regulation.

An external energy economics expert, who was unaffiliated with the study, called the analysis a “highly valuable addition” after a long period in which segments of the car industry argued there was too little data to accurately assess actual CO2 output.

“These findings demonstrate, without question, that the difference in lab and real-world PHEV energy use and CO₂ output is much, much larger than for petrol or diesel cars,” they said. “All policy adjustments concerning PHEVs should be implemented with extreme caution and in the light of that data.”