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Plug-in hybrid electric vehicles emit nearly five times greater planet-heating emissions than lab-reported data indicate, as per a new report.

Widening Gap Between Lab and Actual CO2 Output

Data shows that PHEVs release only 19% less CO₂ than conventional gas and diesel cars, according to analysis carried out by a advocacy organization. That differs significantly with laboratory tests, which suggested a three-quarters reduction in emissions.

Researchers examined data from in-vehicle energy use meters of eight hundred thousand cars sold 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, up from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” stated a lead analyst participating in the study. “This discrepancy is widening and creates a serious problem. Consequently, PHEVs pollute nearly as much as petrol cars.”

Key Factors Behind the Discrepancy

Analysts linked most of the difference to overestimates of the “utility factor” – the ratio of miles travelled in battery mode relative to total mileage. The team found that just 27% of travel was done in EV mode, whereas lab assumptions assumed 84%.

Even, when operating in electric mode, pollution levels were significantly higher than lab projections. That occurred because EV motors were not strong sufficient to function alone, leading to combustion motors using fossil fuels for almost one-third of the distance covered in electric mode.

Policy and Financial Implications

According to estimates, the underestimation of PHEV CO2 output allowed four large automaker groups to escape more than €5bn in fines from 2021 and 2023, by artificially simplifying adherence with EU average fleet CO₂ standards.

Furthermore, drivers of PHEVs could pay about €500 more annually in running costs than would be estimated under lab tests.

“The strong claims that manufacturers often promote about their PHEV cars are obviously far from the mark,” commented a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are helping the environment and cutting costs. Actually, PHEVs are only slightly better than regular petrol and diesel cars in terms of energy use, CO₂ emissions, and operating expenses.”

Political Discussion and Industry Lobbying

Plug-in hybrid cars have recently been brought again into political discussions as automakers have lobbied the European Union to relax CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced intense pressure from the car sector and opposition from EU countries with large automotive manufacturing.

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

An external energy economics specialist, who was unaffiliated with the study, described the report a “very useful contribution” after years in which segments of the automotive industry argued there was too little information to accurately evaluate actual emissions.

“The results demonstrate, beyond any doubt, that the difference in lab and actual PHEV fuel consumption and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” they stated. “Any policy adjustments concerning PHEVs should be implemented with utmost caution and considering this data.”