Plug-in Hybrid Cars Emit Nearly as Heavily as Petrol Vehicles, Study Reveals

Plug-in hybrid electric vehicles produce nearly 5x greater global warming pollution than official figures indicate, according to a new analysis.

Widening Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs release just one-fifth lower CO₂ than traditional gas and diesel cars, according to research carried out by a non-profit group. That contrasts sharply with lab estimates, which suggested a three-quarters decrease in pollution.

Researchers studied data from in-vehicle energy use monitors of 800,000 cars sold in Europe from 2021 and 2023. The team discovered that actual CO₂ emissions from PHEVs in 2023 were 4.9 times higher than official estimates, up from 3.5 times in 2021.

“Real-world emissions are increasing, while official figures are decreasing,” stated a lead researcher involved in the study. “That gap is growing and poses a significant issue. As a result, PHEVs emit almost as heavily as gasoline cars.”

Key Reasons Behind the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “electric driving share” – the percentage of kilometers driven in electric power compared to total mileage. They determined that only a quarter of travel was done in electric mode, whereas official estimates assumed over four-fifths.

Additionally, when running in electric mode, emission levels were well above official estimates. This occurred because electric motors were insufficiently powerful enough to function alone, resulting to engines using gasoline for almost one-third of the distance covered in EV mode.

Policy and Economic Implications

Based on estimates, the underestimation of PHEV emissions allowed four large automaker groups to escape over €5bn in fines from 2021 and 2023, by falsely simplifying adherence with European Union average fleet CO₂ targets.

Furthermore, drivers of PHEVs would pay approximately €500 extra per year in running expenses than would be assumed under laboratory tests.

“The bold claims that automakers often promote about their PHEV cars are clearly far from the truth,” stated a transport expert. “Buyers are being misled into thinking that by buying a PHEV, they are benefiting the planet and cutting costs. Actually, PHEVs are only slightly improved than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and running costs.”

Political Debate and Industry Lobbying

Hybrid vehicles have recently been drawn again into policy discussions as carmakers have pressed the EU to weaken CO₂ standards. A proposed ban on sales of new internal combustion cars in 2035 has faced intense pressure from the car industry and opposition from EU countries with significant automotive industries.

Several senior officials have suggested plug-in hybrids as a potential “compromise” solution to include in the legislation.

An external energy policy expert, who was unaffiliated with the research, called the report a “very useful addition” after years in which parts of the car sector argued there was too little data to accurately assess real-world CO2 output.

“The results demonstrate, beyond any doubt, that the gap between official and actual PHEV energy use and CO₂ output is significantly greater than for gasoline or diesel cars,” the expert said. “All policy changes regarding PHEVs should be implemented with utmost caution and considering this data.”