Plug-in Hybrid Cars Pollute Nearly as Much as Gasoline Cars, Study Finds

PHEVs emit almost five times more planet-heating pollution than lab-reported figures show, according to a recent analysis.

Widening Discrepancy Between Official and Real-World Emissions

Data shows that PHEVs release just 19% lower CO₂ than conventional gas and diesel cars, based on research carried out by a advocacy organization. That differs significantly with laboratory tests, which suggested a 75% reduction in pollution.

Researchers studied data from onboard energy use meters of eight hundred thousand vehicles registered in the EU from 2021 and 2023. The team discovered that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official figures, increased from three and a half times in 2021.

“Actual emissions are rising, while lab-reported emissions are decreasing,” said a senior researcher participating in the study. “That gap is widening and creates a serious problem. As a result, PHEVs emit nearly as much as gasoline vehicles.”

Key Reasons Driving the Emissions Gap

Researchers linked most of the difference to overestimates of the “electric driving share” – the ratio of miles driven in electric mode compared to overall distance. They determined that just a quarter of travel was completed in EV mode, whereas official assumptions suggested 84%.

Even, when running in electric mode, emission amounts were significantly higher than lab estimates. This happened because electric motors were not strong sufficient to operate alone, leading to combustion motors burning gasoline for nearly a third of the travel covered in EV mode.

Policy and Economic Consequences

Based on estimates, the lowballing of PHEV CO2 output allowed several large carmaker groups to avoid more than €5bn in penalties between 2021 and 2023, by falsely easing adherence with European Union average fleet CO₂ targets.

Additionally, owners of PHEVs would pay about €500 extra per year in running expenses than would be estimated under lab conditions.

“The strong statements that manufacturers often promote about their PHEV cars are obviously far from the truth,” stated a automotive expert. “Consumers are being duped into believing that by buying a PHEV, they are helping the planet and saving costs. In reality, PHEVs are little better than regular petrol and diesel vehicles in terms of energy consumption, CO₂ production, and operating costs.”

Political Discussion and Industry Pressure

Plug-in hybrid vehicles have lately been drawn back into policy discussions as automakers have pressed the European Union to weaken CO₂ targets. A proposed ban on sales of new combustion engine cars in 2035 has faced heavy pressure from the car industry and resistance from member states with large car manufacturing.

Several high-level officials have suggested PHEVs as a possible “flexibility” solution to include in the legislation.

An independent energy policy expert, who was not involved with the study, described the analysis a “highly valuable addition” after years in which segments of the car industry claimed there was insufficient data to accurately assess actual CO2 output.

“These findings show, without question, that the gap between lab and real-world PHEV energy use and CO₂ emissions is significantly greater than for petrol or diesel vehicles,” the expert said. “Any regulatory adjustments concerning PHEVs should be made with utmost caution and considering that evidence.”