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Plug-in hybrid electric vehicles release nearly five times greater planet-heating pollution than official figures show, according to a new report.

Widening Gap In Lab and Actual CO2 Output

Data reveals that PHEVs release just 19% less CO₂ than conventional gas and diesel vehicles, according to research carried out by a non-profit group. That contrasts significantly with laboratory estimates, which suggested a three-quarters decrease in pollution.

Researchers examined data from onboard fuel consumption meters of eight hundred thousand vehicles sold in the EU between 2021 and 2023. The team found that real-world CO₂ emissions from PHEVs in 2023 were nearly five times higher than official estimates, up from 3.5 times in 2021.

“Actual CO2 output are increasing, while lab-reported emissions are decreasing,” stated a senior analyst involved in the report. “That discrepancy is growing and creates a significant problem. Consequently, PHEVs pollute almost as heavily as gasoline cars.”

Primary Reasons Driving the Emissions Gap

Analysts linked most of the gap to overestimates of the “electric driving share” – the ratio of miles driven in electric power compared to overall mileage. They determined that just 27% of travel was done in EV mode, while official assumptions assumed over four-fifths.

Even, when operating in electric mode, emission levels were significantly higher than lab projections. That occurred because electric motors were insufficiently powerful enough to function independently, resulting to combustion motors burning gasoline for almost one-third of the distance covered in electric mode.

Regulatory and Economic Consequences

According to estimates, the underestimation of PHEV emissions allowed four major automaker companies to escape more than €5bn in penalties from 2021 and 2023, by artificially easing compliance with European Union fleet-average CO₂ targets.

Additionally, drivers of PHEVs would spend approximately €500 extra per year in operating costs than would be estimated under laboratory conditions.

“The bold statements that automakers like to make about their PHEV cars are obviously way off the truth,” stated a transport analyst. “Consumers are being misled into believing that by purchasing a PHEV, they are benefiting the planet and saving costs. In reality, PHEVs are little better than regular gas and diesel cars in terms of fuel use, CO₂ production, and running expenses.”

Policy Discussion and Industry Lobbying

Plug-in hybrid cars have recently been drawn again into political discussions as carmakers have pressed the European Union to weaken CO₂ standards. A proposed prohibition on sales of new internal combustion cars in 2035 has faced intense lobbying from the automotive sector and resistance from EU countries with large automotive industries.

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

An independent energy economics expert, who was unaffiliated with the study, described the analysis a “highly valuable addition” after years in which segments of the car sector claimed there was too little information to accurately evaluate real-world emissions.

“The results show, without question, that the gap between lab and actual PHEV energy use and CO₂ output is significantly larger than for gasoline or conventional cars,” they said. “Any regulatory adjustments concerning PHEVs should be made with utmost caution and in the light of that data.”