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Plug-in hybrid cars release nearly five times greater global warming emissions than official data indicate, as per a recent report.

Widening Gap Between Lab and Real-World CO2 Output

Data reveals that PHEVs emit only 19% less CO₂ than traditional petrol and diesel vehicles, based on research carried out by a non-profit group. This contrasts significantly with lab estimates, which assumed a three-quarters decrease in pollution.

Analysts studied data from in-vehicle energy use monitors of 800,000 cars registered in Europe between 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official figures, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are decreasing,” said a lead analyst participating in the report. “That gap is widening and creates a significant problem. Consequently, PHEVs emit nearly as heavily as gasoline cars.”

Key Reasons Driving the Discrepancy

Researchers linked most of the difference to overestimates of the “utility factor” – the ratio of kilometers travelled in battery mode compared to overall mileage. The team determined that just 27% of travel was done in electric mode, whereas official assumptions suggested 84%.

Additionally, when running in EV mode, pollution levels were well above official estimates. That occurred because electric motors were insufficiently powerful enough to operate alone, leading to engines burning gasoline for almost a third of the travel covered in electric mode.

Policy and Economic Consequences

Based on estimates, the underestimation of PHEV emissions enabled several major carmaker companies to escape over €5bn in penalties between 2021 and 2023, by artificially easing adherence with EU average fleet CO₂ standards.

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

“The bold statements that automakers like to make about their plug-in hybrid vehicles are clearly far from the mark,” stated a automotive analyst. “Buyers are being misled into believing that by purchasing a PHEV, they are benefiting the environment and saving costs. In reality, PHEVs are only slightly better than standard petrol and diesel cars in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Discussion and Automotive Pressure

Hybrid cars have recently been drawn again into policy discussions as carmakers have pressed the European Union to weaken CO₂ targets. A planned prohibition on sales of new internal combustion vehicles in 2035 has faced heavy pressure from the car sector and resistance from EU countries with large car manufacturing.

Several high-level politicians have suggested PHEVs as a potential “flexibility” solution to introduce in the legislation.

One independent energy policy specialist, who was unaffiliated with the study, called the analysis a “highly valuable addition” after a long period in which segments of the car industry claimed there was insufficient data to accurately evaluate real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the difference between official and actual PHEV fuel consumption and CO₂ output is much, much larger than for petrol or conventional cars,” the expert stated. “Any policy adjustments concerning PHEVs should be made with utmost caution and considering that evidence.”