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PHEVs produce almost five times greater planet-heating pollution than lab-reported data show, according to a new analysis.

Growing Gap In Official and Actual CO2 Output

Statistics reveals that PHEVs emit only 19% lower CO₂ than traditional petrol and diesel cars, according to analysis carried out by a advocacy organization. That contrasts significantly with laboratory tests, which assumed a 75% decrease in pollution.

Researchers examined data from in-vehicle energy use monitors of 800,000 cars sold in the EU from 2021 and 2023. They found that real-world CO₂ output from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported emissions are falling,” said a senior researcher participating in the report. “That gap is widening and creates a serious problem. As a result, PHEVs emit almost as much as gasoline cars.”

Primary Factors Driving the Discrepancy

Analysts attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in battery mode relative to total mileage. They determined that only a quarter of travel was completed in EV mode, whereas official assumptions assumed 84%.

Even, when running in electric mode, pollution amounts were significantly higher than lab estimates. That occurred because electric motors were not strong enough to function alone, resulting to combustion motors burning gasoline for almost a third of the travel covered in EV mode.

Regulatory and Financial Implications

According to calculations, the underestimation of PHEV emissions allowed four large automaker groups to escape more than €5bn in fines between 2021 and 2023, by artificially simplifying compliance with EU fleet-average CO₂ targets.

Additionally, drivers of PHEVs would spend about €500 extra per year in operating costs than would be estimated under lab conditions.

“The bold statements that automakers often promote about their PHEV vehicles are clearly way off the mark,” commented a transport expert. “Consumers are being misled into believing that by purchasing a PHEV, they are helping the planet and saving money. In reality, PHEVs are only slightly better than standard petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Policy Discussion and Automotive Lobbying

Hybrid vehicles have recently been drawn back into political debates as automakers have lobbied the EU to relax CO₂ standards. A planned ban on sales of new combustion engine vehicles in 2035 has faced heavy pressure from the car sector and opposition from EU countries with significant car industries.

Some high-level officials have suggested plug-in hybrids as a possible “flexibility” option to include in the legislation.

One external energy policy specialist, who was not involved with the research, described the analysis a “highly valuable contribution” after years in which parts of the automotive sector argued there was too little data to properly assess actual CO2 output.

“These findings demonstrate, without question, that the difference in lab and actual PHEV fuel consumption and CO₂ output is much, much larger than for gasoline or conventional vehicles,” the expert stated. “All policy adjustments concerning PHEVs should be made with extreme care and considering that data.”