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Plug-in hybrid electric vehicles emit almost 5x more global warming pollution than official figures indicate, as per a recent analysis.

Widening Gap In Official and Actual CO2 Output

Statistics shows that PHEVs emit just one-fifth lower CO₂ than traditional gas and diesel cars, based on research carried out by a non-profit organization. That differs sharply with lab estimates, which suggested a three-quarters reduction in emissions.

Analysts studied data from onboard fuel consumption meters of 800,000 cars registered in the EU between 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are rising, while lab-reported figures are decreasing,” said a lead analyst involved in the study. “That discrepancy is widening and poses a serious problem. As a result, PHEVs pollute nearly as much as gasoline cars.”

Primary Reasons Behind the Discrepancy

Researchers attributed most of the difference to inflated estimates of the “electric driving share” – the percentage of miles driven in electric mode compared to overall mileage. The team determined that just 27% of driving was done in electric mode, while official estimates assumed 84%.

Additionally, when operating in EV mode, pollution levels were well above lab estimates. This happened because electric motors were insufficiently powerful sufficient to operate alone, leading to combustion motors burning gasoline for nearly one-third of the travel completed in electric mode.

Policy and Economic Consequences

According to estimates, the underestimation of PHEV CO2 output enabled four major carmaker companies to avoid more than €5bn in penalties from 2021 and 2023, by falsely simplifying compliance with European Union fleet-average CO₂ targets.

Furthermore, drivers of PHEVs would pay about €500 extra per year in operating costs than is estimated under laboratory conditions.

“The strong statements that manufacturers often promote about their plug-in hybrid vehicles are clearly far from the truth,” stated a transport expert. “Consumers are being misled into thinking that by purchasing a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are only slightly better than standard petrol and diesel cars in terms of energy use, CO₂ emissions, and operating costs.”

Policy Discussion and Automotive Pressure

Plug-in hybrid vehicles have recently been brought again into policy discussions as carmakers have pressed the EU to weaken CO₂ targets. A planned ban on sales of new combustion engine vehicles in 2035 has faced intense pressure from the automotive sector and opposition from EU countries with large automotive manufacturing.

Some high-level politicians have proposed plug-in hybrids as a possible “compromise” option to introduce in the legislation.

One external energy policy expert, who was not involved with the study, described the analysis a “highly valuable addition” after years in which parts of the car sector argued there was insufficient information to accurately assess actual emissions.

“The results show, beyond any doubt, that the gap between lab and actual PHEV energy use and CO₂ output is much, much larger than for petrol or conventional cars,” the expert stated. “Any policy adjustments regarding PHEVs should be implemented with extreme caution and considering that evidence.”