Plug-in Hybrid Vehicles Emit Almost as Heavily as Gasoline Vehicles, Study Finds

PHEVs emit almost five times greater global warming pollution than lab-reported figures indicate, as per a recent report.

Growing Discrepancy In Official and Actual CO2 Output

Data reveals that PHEVs release only 19% less CO₂ than traditional gas and diesel vehicles, according to research conducted by a non-profit group. That contrasts significantly with lab tests, which suggested a three-quarters decrease in pollution.

Analysts studied information from in-vehicle energy use monitors of 800,000 vehicles registered in Europe from 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, increased from three and a half times in 2021.

“Real-world CO2 output are rising, while official emissions are falling,” said a senior analyst participating in the study. “That discrepancy is growing and poses a serious problem. Consequently, PHEVs emit almost as much as petrol cars.”

Key Reasons Driving the Emissions Gap

Analysts attributed the majority of the difference to inflated estimates of the “utility factor” – the ratio of miles driven in battery mode compared to overall mileage. The team determined that only 27% of travel was completed in electric mode, while official assumptions assumed 84%.

Additionally, when operating in EV mode, pollution levels were significantly higher than official estimates. That occurred because electric motors were insufficiently powerful enough to operate alone, resulting to engines using gasoline for almost a third of the distance completed in electric mode.

Regulatory and Economic Consequences

Based on estimates, the lowballing of PHEV emissions allowed four large carmaker groups to escape more than €5bn in penalties between 2021 and 2023, by artificially easing compliance with European Union average fleet CO₂ targets.

Additionally, drivers of PHEVs could pay approximately €500 extra annually in running expenses than is estimated under lab conditions.

“The bold claims that automakers like to make about their PHEV cars are clearly way off the mark,” commented a transport expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting money. In reality, PHEVs are only slightly improved than standard petrol and diesel vehicles in terms of fuel use, CO₂ production, and running costs.”

Political Debate and Automotive Lobbying

Plug-in hybrid vehicles have recently been brought back into policy debates as carmakers have lobbied the European Union to relax CO₂ targets. A planned prohibition on sales of new combustion engine cars in 2035 has faced intense pressure from the car industry and opposition from EU countries with large automotive manufacturing.

Several senior officials have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

One external energy economics expert, who was unaffiliated with the study, called the analysis a “very useful contribution” after a long period in which segments of the car sector claimed there was too little information to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap in official and real-world PHEV energy use and CO₂ emissions is significantly greater than for gasoline or conventional vehicles,” the expert said. “All policy changes regarding PHEVs should be made with utmost care and in the light of this evidence.”