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

Plug-in hybrid electric vehicles release nearly 5x more global warming emissions than official figures show, according to a new analysis.

Growing Gap In Lab and Real-World Emissions

Data reveals that PHEVs emit just one-fifth lower CO₂ than traditional petrol and diesel cars, based on analysis conducted by a non-profit organization. That differs significantly with lab estimates, which suggested a three-quarters reduction in pollution.

Analysts examined information from in-vehicle fuel consumption meters of eight hundred thousand cars sold in the EU between 2021 and 2023. The team found that actual CO₂ emissions from PHEVs in 2023 were 4.9 times greater than lab estimates, increased from 3.5 times in 2021.

“Real-world CO2 output are increasing, while lab-reported figures are falling,” said a senior researcher involved in the study. “This gap is growing and poses a significant issue. Consequently, PHEVs emit nearly as much as petrol vehicles.”

Primary Factors Behind the Emissions Gap

Analysts attributed most of the difference to overestimates of the “electric driving share” – the ratio of miles travelled in electric mode compared to total mileage. The team determined that only a quarter of travel was done in EV mode, while official assumptions suggested 84%.

Additionally, when operating in EV mode, pollution levels were well above official projections. That happened because electric motors were insufficiently powerful enough to function alone, resulting to combustion motors burning gasoline for nearly a third of the distance covered in EV mode.

Policy and Financial Consequences

Based on calculations, the underestimation of PHEV CO2 output enabled four major automaker groups to avoid more than €5bn in fines from 2021 and 2023, by artificially simplifying compliance with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs would pay about €500 more per year in running expenses than would be assumed under laboratory tests.

“The strong statements that manufacturers like to make about their plug-in hybrid vehicles are obviously far from the truth,” stated a automotive expert. “Consumers are being misled into thinking that by buying a PHEV, they are benefiting the environment and saving costs. Actually, PHEVs are little better than standard gas and diesel vehicles in terms of fuel consumption, CO₂ emissions, and operating expenses.”

Political Discussion and Automotive Pressure

Hybrid cars have recently been brought again into policy debates as carmakers have lobbied the EU to weaken CO₂ targets. A planned prohibition on sales of new internal combustion cars in 2035 has faced heavy lobbying from the automotive sector and resistance from EU countries with large automotive manufacturing.

Some senior officials have suggested plug-in hybrids as a potential “flexibility” option to introduce in the regulation.

One independent energy economics specialist, who was unaffiliated with the research, called the report a “very useful addition” after years in which parts of the car sector claimed there was insufficient data to properly assess real-world CO2 output.

“These findings demonstrate, beyond any doubt, that the gap between official and real-world PHEV energy use and CO₂ output is significantly larger than for petrol or conventional vehicles,” the expert stated. “Any policy changes concerning PHEVs should be implemented with extreme caution and in the light of that evidence.”